Reply
 
Thread Tools Display Modes
  #51  
Old 07-12-2018, 02:30 PM
DPRK DPRK is online now
Guest
 
Join Date: May 2016
Posts: 2,155
Quote:
Originally Posted by scr4 View Post
True, but I would concede that for climate control, 1F precision is sufficient, but 1C can be marginal. AC thermostats in Japan typically have 0.5C steps, and I think that's very much desirable. I've been in situations where setting it to 25.0 seemed too cool and 26.0 too warm.
Hmm. Room temperature is a nebulous standard; there is no way it is precisely defined to within 1 degree or 0.5 degree (and does the ventilation system even keep the air mixed that well?) Recommended temperatures are always given as ranges depending on the season, humidity, and possibly other considerations. Also, if 25.0 seems too cool, I would suggest wearing at least a T-shirt.
  #52  
Old 07-12-2018, 02:32 PM
beowulff's Avatar
beowulff beowulff is online now
Member
 
Join Date: May 2001
Location: Scottsdale, more-or-less
Posts: 16,018
Quote:
Originally Posted by rat avatar View Post
4 inches vs:
0.33333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 M

4 inches is exact and the metric equivalent is still an approximation.

But once again the issue is that 0.1 does not exist in Floating-Point.


You can stay with rational numbers like 1/3, but a main point of a decimal based system is to get rid of those fractions.
This is a completely ridiculous argument, and has nothing to do with units. All measurement systems will have numbers that can't be represented exactly in binary. So what? It's possible to represent them with any required accuracy.
  #53  
Old 07-12-2018, 02:38 PM
Kobal2's Avatar
Kobal2 Kobal2 is offline
Guest
 
Join Date: Mar 2008
Location: Paris, France
Posts: 17,233
Quote:
Originally Posted by Mogle View Post
you will never ever have exactly 4 inches.

That's what I keep telling my wife, but...
__________________
--- ---
I'm not sure how to respond to this, but that's never stopped me before.
  #54  
Old 07-12-2018, 02:38 PM
rat avatar's Avatar
rat avatar rat avatar is online now
Member
 
Join Date: Dec 2009
Location: Seattle, Wa
Posts: 4,849
Quote:
Originally Posted by rat avatar View Post
4 inches vs:
0.33333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 M

4 inches is exact and the metric equivalent is still an approximation.

But once again the issue is that 0.1 does not exist in Floating-Point.


You can stay with rational numbers like 1/3, but a main point of a decimal based system is to get rid of those fractions.

To add to this, because it is not a reason to not adopt SI units but because the implications are important.

Floating point is a form of finite mathematics and the distributive law and Associative law for multiplication do not always hold in finite math due to these representation errors. This breaks a lot of assumptions by compilers and programmers.

a * ( b * c ) may not equal ( a * b ) * c
a * ( b + c ) may not equal ( a * b ) + ( a * c )

These assumptions not holding will lead to compounding inaccuracies well beyond the issues caused by the normal loss of precision with floating point.

Decimal based systems, which have intrinsic representation errors can be really problematic because of their non-existence in base 2 when converting to smaller prefixes.

This is why banks and other critical users resort to using computationally expensive decimal data types, and why your online loan amortization tool, phone app or calculator never seems to match your statement.
  #55  
Old 07-12-2018, 02:43 PM
rat avatar's Avatar
rat avatar rat avatar is online now
Member
 
Join Date: Dec 2009
Location: Seattle, Wa
Posts: 4,849
Quote:
Originally Posted by beowulff View Post
This is a completely ridiculous argument, and has nothing to do with units. All measurement systems will have numbers that can't be represented exactly in binary. So what? It's possible to represent them with any required accuracy.
The pound is 16 ounces, the mile is 5280 feet, where the base prefixes in the Metric system are hard tied to a number that can't be represented in binary in the metric system. Or in other words, any move to a smaller sized unit has a rounding event.


Code:
exa	E	1000000000000000000	10^18
peta	P	1000000000000000	10^15
tera	T	1000000000000	10^12
giga	G	1000000000	10^9
mega	M	1000000	10^6
kilo	k	1000	10^3
hecto	h	100	10^2
deca	da	10	10^1
(none)	(none)	1	10^0
deci	d	0.1	10^−1
centi	c	0.01	10^−2
milli	m	0.001	10^−3
micro	μ	0.000001	10^−6
nano	n	0.000000001	10^−9
pico	p	0.000000000001	10^−12
femto	f	0.000000000000001	10^−15
atto	a	0.000000000000000001	10^−18

Are you really suggesting people don't use the prefixes of the system? Once again, I am not anti SI, but I can go from a mile to an inch and even to a mil with no loss in precision, but I can't do the same for a meter to a centimeter.

SI isn't a bad system, but it has very real limitations with very real implications.

Last edited by rat avatar; 07-12-2018 at 02:48 PM.
  #56  
Old 07-12-2018, 02:45 PM
Lemur866's Avatar
Lemur866 Lemur866 is online now
Charter Member
 
Join Date: Jul 2000
Location: The Middle of Puget Sound
Posts: 22,199
Quote:
Originally Posted by rat avatar View Post
4 inches vs:
0.33333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 M

4 inches is exact and the metric equivalent is still an approximation.

But once again the issue is that 0.1 does not exist in Floating-Point.


You can stay with rational numbers like 1/3, but a main point of a decimal based system is to get rid of those fractions.
Yes. So you can write 6 feet 4 inches, and it's exactly 6 and 1/3 feet.

So?

Yes, we have a name for a 1/12th of a foot. It's called an inch. How does giving 1/12th of a foot a name help us avoid rounding errors?

Any decimal expansion rounding error that applies to meters also applies to feet, inches, miles, furlongs, parsecs, light years, chains, rods, yards, leagues, or fathoms.

Again, you're not understanding the problem. You can write 4 feet 4 inches, and get exactly 4 and 1/3 feet. That doesn't give you a precise decimal expansion of 4.333333333... feet. It just gives you another way to write 4 1/3 feet. If you need to keep that fraction, then keep the fraction. You can use precise fraction with any unit. One third of a meter. One third of an inch. One third of a yard. One third of a furlong. One third of a light year. The fact that some of these fractional units are equivalent to integer values of other units is completely irrelevant! It doesn't matter that there's a vernacular name for 1/3 of a yard, but no name for 1/3 of a light year. If you absolutely positively must preserve that exact fraction, then preserve that goddam exact fraction.

Again, the only way you can preserve those exact fractions in a traditional system is to...preserve those exact fractions, and write them out as fractions, and then give them a special name so that instead of a fraction you've got an integer. Writing six feet four inches is EXACTLY THE SAME THING as writing six and one third feet.

Metric has nothing to do with it. Seriously. The only thing is that there are traditional names for some fractions of some traditional units, and there are not such traditional names for metric units. And? The fact that there is no name for one third of a meter is not a problem, just like the fact that there is no name for one third of a chain or one third of a rod or one third of a light year.

And of course, all these standardization of traditional units happened by happenstance. Different people used different traditional measures for different reasons, and it didn't matter how many firkens were in a hogshead, because there was no precise definition of a hogshead anyway. Then along came the industrial revolution, and we had to measure precisely how big a hogshead was, and then how many drams that equaled, and maybe we'll fudge the sizes so the relationships are integer multiples of each other.

Yes, there is no exact binary representation for 1/10th. There is also no exact binary representation for 1/7th. If those French Revolutionaries would have known that we were going to be using binary, they should have made metric hexadecimal rather than decimal, but they didn't. However, the fact that we have decimal names for things in the metric system doesn't make metric unsuited to binary representation, because traditional measurements have the exact same problem, you can't represent 1/10th of an ounce in binary either. Oh, there's no traditional named unit that's 1/10th of an ounce? And there is one that's 1/6th of an ounce? So what? How does that help? Oh, you can keep track of exact fractions using mixes of two named units and thus get integer representations of fractions? Guess what else gives you integer representations of fractions? Integer representation of fractions.
  #57  
Old 07-12-2018, 02:55 PM
ctnguy ctnguy is offline
Guest
 
Join Date: Sep 2008
Location: Cape Town
Posts: 917
Quote:
Originally Posted by senoy View Post
I've never thought about the decile thing. How do Celsius countries do it? If asked the temperature, we'll frequently give the decile. "It's going to be up in the 90s today." Or "It's going to be in the 40s tonight." What do you Celsius people do? Just refer to the actual projected high or low? If I say it's going to be in the 70s, that means something to most people. Do you say the low 20s? What if you're trying to differentiate between the low and the high decile? Does that just not happen? I'm actually interested.
Speaking only for myself, and from a Mediterranean-type climate that never freezes: I think most often I say something like "it's going to be about 25 today" or "it's going to drop to about 12 degrees tonight". For higher temperatures, often something like "over 30", "over 35", "over 40", as the case may be. Similarly for cold temperatures, "it's going to be under 10 tonight".
  #58  
Old 07-12-2018, 03:01 PM
rat avatar's Avatar
rat avatar rat avatar is online now
Member
 
Join Date: Dec 2009
Location: Seattle, Wa
Posts: 4,849
Quote:
Originally Posted by Lemur866 View Post
Yes. So you can write 6 feet 4 inches, and it's exactly 6 and 1/3 feet.

So?

Yes, we have a name for a 1/12th of a foot. It's called an inch. How does giving 1/12th of a foot a name help us avoid rounding errors?

Any decimal expansion rounding error that applies to meters also applies to feet, inches, miles, furlongs, parsecs, light years, chains, rods, yards, leagues, or fathoms.

Again, you're not understanding the problem. You can write 4 feet 4 inches, and get exactly 4 and 1/3 feet. That doesn't give you a precise decimal expansion of 4.333333333... feet. It just gives you another way to write 4 1/3 feet. If you need to keep that fraction, then keep the fraction. You can use precise fraction with any unit. One third of a meter. One third of an inch. One third of a yard. One third of a furlong. One third of a light year. The fact that some of these fractional units are equivalent to integer values of other units is completely irrelevant! It doesn't matter that there's a vernacular name for 1/3 of a yard, but no name for 1/3 of a light year. If you absolutely positively must preserve that exact fraction, then preserve that goddam exact fraction.

Again, the only way you can preserve those exact fractions in a traditional system is to...preserve those exact fractions, and write them out as fractions, and then give them a special name so that instead of a fraction you've got an integer. Writing six feet four inches is EXACTLY THE SAME THING as writing six and one third feet.

Metric has nothing to do with it. Seriously. The only thing is that there are traditional names for some fractions of some traditional units, and there are not such traditional names for metric units. And? The fact that there is no name for one third of a meter is not a problem, just like the fact that there is no name for one third of a chain or one third of a rod or one third of a light year.

And of course, all these standardization of traditional units happened by happenstance. Different people used different traditional measures for different reasons, and it didn't matter how many firkens were in a hogshead, because there was no precise definition of a hogshead anyway. Then along came the industrial revolution, and we had to measure precisely how big a hogshead was, and then how many drams that equaled, and maybe we'll fudge the sizes so the relationships are integer multiples of each other.

Yes, there is no exact binary representation for 1/10th. There is also no exact binary representation for 1/7th. If those French Revolutionaries would have known that we were going to be using binary, they should have made metric hexadecimal rather than decimal, but they didn't. However, the fact that we have decimal names for things in the metric system doesn't make metric unsuited to binary representation, because traditional measurements have the exact same problem, you can't represent 1/10th of an ounce in binary either. Oh, there's no traditional named unit that's 1/10th of an ounce? And there is one that's 1/6th of an ounce? So what? How does that help? Oh, you can keep track of exact fractions using mixes of two named units and thus get integer representations of fractions? Guess what else gives you integer representations of fractions? Integer representation of fractions.
Is the foot, the mile or the inch based on 1/7? No.

But yes, like I said up thread, had they ignored the thumbs and been octal, or even duodecimal or hexadecimal some modern problems would be easier to solve.

There are some problems like calculating the stable Lagrange points for the asteroid belt with the influences of Jupiter and Mars which are unsolvable in practical compute timelines due to these limitations. JPL has even reduced the precision of their ephemerides due to compute time because they have to use arb precision to get more accurate results which is not hardware accelerated. It may be easy to say just move to another number base, but we have a century of proofs often in non-linear domains that does not allow for this without a lot of work.

But lets be clear, I was responding to people making the claim that there is no reason for someone to use the customary units, but when you are a machinist building an airplane that is a few meters across, and your tolerances need to be within 25.40 μm (1 mil) if you use the customary units your job is a lot easier.

As I have stated multiple times that all systems have their limitations, but some systems have intrinsic limitations. So I don't know what your post relates to my claim anyway.

All systems have flaws, and this is one of the Metric system, and as I stated before the dollar has similar challenges in modern computer based world.The post I was replying to was pointing out that there are lots of use cases where this loss in precision is problematic, and that it can't just be ignored.

Last edited by rat avatar; 07-12-2018 at 03:05 PM.
  #59  
Old 07-12-2018, 03:01 PM
Nava Nava is online now
Guest
 
Join Date: Nov 2004
Location: Hey! I'm located! WOOOOW!
Posts: 39,800
Quote:
Originally Posted by senoy View Post
Yes, but 1 atmosphere is based on standard gravity which is a calculated average gravity at sea level. That's why water boils at very close to 100 at Sea Level and at 95 in Denver.
But it's not constant; the whole weather report is based on its variations, yet you speak as if it were constant.

And the 100ºC also requires distilled water, which isn't normally what's used for cooking.


Quote:
Originally Posted by senoy View Post
I've never thought about the decile thing. How do Celsius countries do it? If asked the temperature, we'll frequently give the decile. "It's going to be up in the 90s today." Or "It's going to be in the 40s tonight." What do you Celsius people do? Just refer to the actual projected high or low? If I say it's going to be in the 70s, that means something to most people. Do you say the low 20s? What if you're trying to differentiate between the low and the high decile? Does that just not happen? I'm actually interested.
How do you give someone's approximate age? The same expressions are used in Spanish. Couple of examples from Spain: Hoy hará... veintitantos (today it's.. twentysomething). ¿A cuánto estamos? Pues no sé, pero diría que veintimucho. (What's the temp? Dunnow but I'm guessing twentylots.) And "under 36" or "over 36" are of course important, that being more or less body temp (actual body temp will vary by person, time of day and health status). ¿Qué hace ahi fuera? ¡Más de 36 y subiendo! (how hot is it out there? Over 36 and climbing!)
__________________
Evidence gathered through the use of science is easily dismissed through the use of idiocy. - Czarcasm.

Last edited by Nava; 07-12-2018 at 03:06 PM.
  #60  
Old 07-12-2018, 03:05 PM
Kobal2's Avatar
Kobal2 Kobal2 is offline
Guest
 
Join Date: Mar 2008
Location: Paris, France
Posts: 17,233
Quote:
Originally Posted by rat avatar View Post
4 inches vs:
0.33333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 M

4 inches is exact and the metric equivalent is still an approximation.

And ? 1m = 39.3701 inches = 3.28084 feet. Y'all don't have an exact measure of this specific, arbitrary distance wot my unit system is based on, so yours is pure shite !1!!
(I jest, of course, but you get my point, right ?)
__________________
--- ---
I'm not sure how to respond to this, but that's never stopped me before.
  #61  
Old 07-12-2018, 03:11 PM
rat avatar's Avatar
rat avatar rat avatar is online now
Member
 
Join Date: Dec 2009
Location: Seattle, Wa
Posts: 4,849
Quote:
Originally Posted by Kobal2 View Post
And ? 1m = 39.3701 inches = 3.28084 feet. Y'all don't have an exact measure of this specific, arbitrary distance wot my unit system is based on, so yours is pure shite !1!!
(I jest, of course, but you get my point, right ?)
Not the base units or divisions, and it is a straw man to even suggest I am debasing the metric system. I said it is the best option for world standards multiple times.

But 1 foot = 0.3048 meters exactly.

As this is GQ, can you please point out where is said the metric system is pure shite !1!!? Or can you provide a cite that shows that my descriptions of the limitations (which all systems have) do not exist? I am quite confident I am being factually correct.

I'll bow out of this thread, as I forgot how passionate people are about this subject and it appears that talking about the historical justifications, and limitations of systems of measure is impractical.

But an accumulating loss in precision is a very real problem, especially when it is unavoidable by a particular system.

Last edited by rat avatar; 07-12-2018 at 03:14 PM.
  #62  
Old 07-12-2018, 03:13 PM
Nava Nava is online now
Guest
 
Join Date: Nov 2004
Location: Hey! I'm located! WOOOOW!
Posts: 39,800
Partial repeat, OOT in previous post.

Quote:
Originally Posted by senoy View Post
I've never thought about the decile thing. How do Celsius countries do it? If asked the temperature, we'll frequently give the decile. "It's going to be up in the 90s today." Or "It's going to be in the 40s tonight." What do you Celsius people do? Just refer to the actual projected high or low? If I say it's going to be in the 70s, that means something to most people. Do you say the low 20s? What if you're trying to differentiate between the low and the high decile? Does that just not happen? I'm actually interested.
How do you give someone's approximate age? The same expressions are used in Spanish. Couple of examples from Spain: Hoy hará... veintitantos (today it's.. twentysomething). ¿A cuánto estamos? Pues no sé, pero diría que veintimucho. (What's the temp? Dunnow but I'm guessing twentylots.) And "under 36" or "over 36" are of course important, that being more or less body temp (actual body temp will vary by person, time of day and health status). ¿Qué hace ahi fuera? ¡Más de 36 y subiendo! (how hot is it out there? Over 36 and climbing!)

One of the signs of a bad translator or adapter (which may actually mean a bad editor) is that they've converted temperatures and not used the usual rounding. "He had a high fever, above 38C" in a British edition becomes "he had a high fever, above 100.4F" in the American edition. Because yeah, the decimal is what's sooooo important.

Last edited by Nava; 07-12-2018 at 03:14 PM.
  #63  
Old 07-12-2018, 03:17 PM
Kobal2's Avatar
Kobal2 Kobal2 is offline
Guest
 
Join Date: Mar 2008
Location: Paris, France
Posts: 17,233
Quote:
Originally Posted by Orwell View Post
I cook a lot, actually. I know I like to cook my steaks to 125 and I like to BBQ at 225 to 250. I bake stuff at 350 most of the time, but sometimes at 300, 325, 400 or 425.

When I need to boil water, I heat it until I see the bubbles coming to the top. I don't stick a thermometer in it to see if it is 212 F or 100 C. When I need to freeze something, I stick it in the freezer until it's solid. No measurement necessary.

I was referring to teaspoons, tablespoons, etc. I think it would be much easier to use 5ml, 10ml, etc when trying to halve or double a recipe.

Don't worry boo, metric cookbook writers still use obnoxiously vague "units" like a pinch, a dash, a sprinkle, a spritz, "as needed" (if I knew how much was needed I wouldn't need to buy a fucking recipe, now would I ?!), a cup (FUCK YOU, that's the whole *point* of using a standardized unit system !), to taste (fuck you, did you put spme in that dish when I ate it in your restaurant or not ?!) and so on.
This is because professional cooks are universally assholes who don't want you to succeed and revel in the knowledge that your soufflé is going to be a fucking disaster.
__________________
--- ---
I'm not sure how to respond to this, but that's never stopped me before.
  #64  
Old 07-12-2018, 03:21 PM
Voyager's Avatar
Voyager Voyager is offline
Charter Member
 
Join Date: Aug 2002
Location: Deep Space
Posts: 44,233
Quote:
Originally Posted by Kobal2 View Post
And ? 1m = 39.3701 inches = 3.28084 feet. Y'all don't have an exact measure of this specific, arbitrary distance wot my unit system is based on, so yours is pure shite !1!!
(I jest, of course, but you get my point, right ?)
That's exactly why people have trouble converting - they don't think in metric units, but only convert. We deal in pounds of meat, but when we lived in Africa my mother had no trouble ordering a kilo of meat or half a kilo. You soon learn what a kilo looks like, just as we've learned what a pound looks like. We all know what a liter of soda looks like, don't we? That it is hard to convert from a 12 oz. can to a liter is not important.

In the US we mostly only deal with metric units once in a while. After my daughter lived in Germany for four years she thought in Centigrade temperatures, and know what was hot and what was cold without converting. In chip design we deal in nanometers, and we don't convert from nanoyards.

As for computers, it is not hard to write a decimal arithmetic package if needed. IBM1620s from the late '50s, early '60s looked like decimal machines. And people seem to be neglecting that changing from pounds to ounces or cups to pints to quarts requires conversion factors for each step, all incompatible, and none derivable from the name of the unit.
  #65  
Old 07-12-2018, 03:21 PM
senoy senoy is online now
Guest
 
Join Date: Feb 2018
Posts: 1,263
Quote:
Originally Posted by Nava View Post
How do you give someone's approximate age? The same expressions are used in Spanish. Couple of examples from Spain: Hoy hará... veintitantos (today it's.. twentysomething). ¿A cuánto estamos? Pues no sé, pero diría que veintimucho. (What's the temp? Dunnow but I'm guessing twentylots.) And "under 36" or "over 36" are of course important, that being more or less body temp (actual body temp will vary by person, time of day and health status). ¿Qué hace ahi fuera? ¡Más de 36 y subiendo! (how hot is it out there? Over 36 and climbing!)
Really? They just say in the 20s? That's a huge range. It goes from comfortable at 20 to hot at nearly 30. If you say in the 20s Celsius, it's not conveying anything. It's like saying that the temp is between 68 and 86 Fahrenheit, that's a huge range that will impact my behavior. If the high is 68, I'm going to pack a jacket. If it's 86, I'm going to bring a fan. In Fahrenheit, the deciles all roughly correspond to a similar temperature range. If it's the 70s, I know that it's a comfortable day. If it's the 80s, I know it's going to be very warm. If it's the 90s, I know it's sweltering. If it's the 60s, it's brisk. If you tell me that it's in the 10s Celsius, it could be a very chilly day to a quite comfortable one. It doesn't seem to be precise to say it that way.
  #66  
Old 07-12-2018, 03:21 PM
Lemur866's Avatar
Lemur866 Lemur866 is online now
Charter Member
 
Join Date: Jul 2000
Location: The Middle of Puget Sound
Posts: 22,199
I still don't understand how computers can more accurately represent traditional units than they can metric units.

The only way this can be true is if you're allowed to mix units. Feet and inches.

Except if your computer system is keeping track of feet and inches as separate values, how are you performing operations on those values?

I guarantee you that if you're using traditional units in your computer system, you're picking one unit and staying with that unit for the whole calculation, because otherwise is madness. You might use feet, but you're calculating everything in feet, not switching between feet and inches.

If someone inputs 5 feet 4 inches, that's fine. Now multiply that by 3, divide by sqrt(2), and multiply by a constant.

You're going to do the math by doing all the operations on 5 feet, and all the operations on 4 inches, and then add the values back together?

Dude, if you do that, then go ahead and do the same thing for thirds of a meter, if it's that important.

Much more likely you get the input in feet and fractional feet, and do one operation on one value, and output one value. And if so, the length of the unit is arbitrary.
  #67  
Old 07-12-2018, 03:24 PM
Voyager's Avatar
Voyager Voyager is offline
Charter Member
 
Join Date: Aug 2002
Location: Deep Space
Posts: 44,233
Quote:
Originally Posted by Kobal2 View Post
Don't worry boo, metric cookbook writers still use obnoxiously vague "units" like a pinch, a dash, a sprinkle, a spritz, "as needed" (if I knew how much was needed I wouldn't need to buy a fucking recipe, now would I ?!), a cup (FUCK YOU, that's the whole *point* of using a standardized unit system !), to taste (fuck you, did you put spme in that dish when I ate it in your restaurant or not ?!) and so on.
This is because professional cooks are universally assholes who don't want you to succeed and revel in the knowledge that your soufflé is going to be a fucking disaster.
They are just being pre Fanny Farmer traditional, back when all recipes were like that because it was expected girls would be taught to cook by their mothers.

I have lots of British recipe books which give both, and either measure works fine.
  #68  
Old 07-12-2018, 03:49 PM
Nava Nava is online now
Guest
 
Join Date: Nov 2004
Location: Hey! I'm located! WOOOOW!
Posts: 39,800
Quote:
Originally Posted by senoy View Post
Really? They just say in the 20s? That's a huge range. It goes from comfortable at 20 to hot at nearly 30. If you say in the 20s Celsius, it's not conveying anything. It's like saying that the temp is between 68 and 86 Fahrenheit, that's a huge range that will impact my behavior. If the high is 68, I'm going to pack a jacket. If it's 86, I'm going to bring a fan. In Fahrenheit, the deciles all roughly correspond to a similar temperature range. If it's the 70s, I know that it's a comfortable day. If it's the 80s, I know it's going to be very warm. If it's the 90s, I know it's sweltering. If it's the 60s, it's brisk. If you tell me that it's in the 10s Celsius, it could be a very chilly day to a quite comfortable one. It doesn't seem to be precise to say it that way.


My specific examples did not include "in the 20s", I have no idea where did you read that one.

"Twentysomething" and "twentylots" are two different ranges. One is low 20s (21 to 24), the other is high 20s (26 to 29).

My apologies if my trying to stick close to the original expressions rather than saying we speak exactly as in English (we don't) confused you.
__________________
Evidence gathered through the use of science is easily dismissed through the use of idiocy. - Czarcasm.
  #69  
Old 07-12-2018, 05:38 PM
krondys krondys is offline
Member
 
Join Date: Apr 2011
Location: Gillette, Wyoming
Posts: 952
Fractional meters are not harder to measure than fractional feet just because they are metric/SI.

Anywho, the decimalized form of metric is appreciated by American surveyors... we just use decimal feet for our measurements.

Also, one foot does not equal .3048 meters exactly... it is 1200/3937 meters! For the standard US Survey foot.
  #70  
Old 07-12-2018, 05:46 PM
scr4 scr4 is online now
Member
 
Join Date: Aug 1999
Location: Alabama
Posts: 14,941
Quote:
Originally Posted by rat avatar View Post
4 inches vs:
0.33333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333 M

4 inches is exact and the metric equivalent is still an approximation.
No. 4 inches is not exact. If you want to be specific, you say 4.0 inches, or 4.00000 inches, or whatever accuracy is appropriate for the situation.
  #71  
Old 07-12-2018, 05:54 PM
rat avatar's Avatar
rat avatar rat avatar is online now
Member
 
Join Date: Dec 2009
Location: Seattle, Wa
Posts: 4,849
Quote:
Originally Posted by scr4 View Post
No. 4 inches is not exact. If you want to be specific, you say 4.0 inches, or 4.00000 inches, or whatever accuracy is appropriate for the situation.
In general.

In a number with a decimal point, trailing zeros are significant.

AND

In a number without a decimal point, trailing zeros may or may not be significant.

4 and 4.0 are different by most convention, and that trailing 0 on 4.0 would tend to signify that it is only acculturate to one decimal place, when it would need infinite zeros to capture all of the precision.

So I am going to need a cite that an integer is not an exact value, or that 12 /3 !=4

Last edited by rat avatar; 07-12-2018 at 05:57 PM.
  #72  
Old 07-12-2018, 06:04 PM
scr4 scr4 is online now
Member
 
Join Date: Aug 1999
Location: Alabama
Posts: 14,941
Quote:
Originally Posted by rat avatar View Post
In general.

In a number with a decimal point, trailing zeros are significant.

AND

In a number without a decimal point, trailing zeros may or may not be significant.

4 and 4.0 are different by most convention, and that trailing 0 on 4.0 would tend to signify that it is only acculturate to one decimal place, when it would need infinite zeros to capture all of the precision.

So I am going to need a cite that an integer is not an exact value, or that 12 /3 !=4
We are talking about unit of measure. "4 inches" is a physical length, not 4 of some countable object. There is no situation where "4 inches" (or 4 meters, or 4 pounds, or 4 light-years, etc) is treated as an exact number.
  #73  
Old 07-12-2018, 06:06 PM
Chronos's Avatar
Chronos Chronos is offline
Charter Member
Moderator
 
Join Date: Jan 2000
Location: The Land of Cleves
Posts: 79,571
Quote:
Quoth rat avatar:

0.33333 of a meter is an approximation and rounding errors do matter.
4 inches is also an approximation, and a much less precise one than 0.33333 meter.

Quote:
Without standard gravity you can't actually accurately derive the newton (kg⋅m/s), pascal (kg⋅m^−1⋅s^−2), watt (kg⋅m2⋅s^−3) or other units.
Of course you can derive all of those without standard gravity. The kilogram is based on a lump of precious metal in Paris (but they're working to do away with that), the second is based on the frequency of light emitted by cesium atoms, and the meter is based on the second and the speed of light, and newtons, pascals, watts, and all the rest are derived from those base units. Standard gravity isn't involved at all.
Quote:
This is why banks and other critical users resort to using computationally expensive decimal data types, and why your online loan amortization tool, phone app or calculator never seems to match your statement.
No, banks use ordinary binary floating point calculations if the programmers were lazy and didn't bother looking up the right way to do it, and binary integer calculations if the programmers did it right. And they don't care at all about the lack of perfect binary representations of some numbers, because nobody ever cares about that much precision in finance. And if you have a calculator on your phone that disagrees with your bank statement, the most likely explanation is that the app writer was an idiot, and the second-most-likely is that the app is using a different compounding period than the bank is, neither of which has anything to do with the way the numbers are represented.
  #74  
Old 07-12-2018, 06:11 PM
scr4 scr4 is online now
Member
 
Join Date: Aug 1999
Location: Alabama
Posts: 14,941
Quote:
Originally Posted by senoy View Post
I've never thought about the decile thing. How do Celsius countries do it?
You only do the "decile thing" when you use units where 10 units is a convenient range. You don't do it with people's height, for example. You just say "around 5 ft 9".
  #75  
Old 07-12-2018, 06:16 PM
rat avatar's Avatar
rat avatar rat avatar is online now
Member
 
Join Date: Dec 2009
Location: Seattle, Wa
Posts: 4,849
A cite, from a book that most people interested in this area probably have access to.

A demonstration on why algebraic properties of floating point are neither associative nor distributive can be found in section 4.2.2 of:

The Art of Computer Programming; Volume 2, Seminumerical Algorithms. - Knuth D. (1969)


Quote:
Floating point computation is by nature inexact, and it is not difficult to misuse
it so that the computed answers consist almost entirely of “noise.” One of the
principal problems of numerical analysis is to determine how accurate the results
of certain numerical methods will be. A “credibility-gap” problem is involved
here: we don’t know how much of the computer’s answers to believe. Novice
computer users solve this problem by implicitly trusting in the computer as an
infallible authority; they tend to believe that all digits of a printed answer are
significant. Disillusioned computer users have just the opposite approach, they
are constantly afraid that their answers are almost meaningless. Many a serious
mathematician has attempted to give rigorous analyses of a sequence of floating
point operations, but has found the task to be so formidable that he has tried
to content himself with plausibility arguments instead.
Quote:
Several familiar rules of algebra are still, of course, conspicuously absent
from the collection of identities above; the associative law for floating point
multiplication is not strictly true, as shown in exercise 3, and the distributive law
between (x) and (+) can fail rather badly
  #76  
Old 07-12-2018, 06:18 PM
scr4 scr4 is online now
Member
 
Join Date: Aug 1999
Location: Alabama
Posts: 14,941
Quote:
Originally Posted by rat avatar View Post
A cite, from a book that most people interested in this area probably have access to.
Nobody is arguing that floating point is as exact as integers. We're just saying we never use integers to represent physical quantities like distance/length. Banking is different, a cent is a countable object (or an abstract concept) and not a physical quantity.

Last edited by scr4; 07-12-2018 at 06:20 PM.
  #77  
Old 07-12-2018, 06:22 PM
Lemur866's Avatar
Lemur866 Lemur866 is online now
Charter Member
 
Join Date: Jul 2000
Location: The Middle of Puget Sound
Posts: 22,199
Quote:
Originally Posted by rat avatar View Post
In general.

In a number with a decimal point, trailing zeros are significant.

AND

In a number without a decimal point, trailing zeros may or may not be significant.

4 and 4.0 are different by most convention, and that trailing 0 on 4.0 would tend to signify that it is only acculturate to one decimal place, when it would need infinite zeros to capture all of the precision.

So I am going to need a cite that an integer is not an exact value, or that 12 /3 !=4
There is no object in the world that is exactly 4 inches long. There might be objects that are 4.0 inches long, or 4.0000 inches long. But there is no such thing as an object that is precisely 4 integer inches long, because measurements don't work that way.

Again, 4 is a perfectly legitimate number. It's my favorite integer. And when I say that I have a 4 inch chef's knife, is that chef's knife 4 integer inches long?

Of course not, because even if those knives are manufactured with unearthly precision, they are going to vary by some number of atoms, they're going to expand or contract based on temperature, and so on.

So 4 is not a precise value for the measurement of a knife. It's a value that means somewhere between 3.5 and 4.5, not something more precise than 4.000000000000000000.

And again, if you need to keep track of integer values for length for some reason, how does the fact that the knife is in inches or feet make it more precise than if it is in centimeters or meters? Yes, you can divide a foot into 12 inches. You can divide a meter into 1/12th of a meter with exactly the same ease.
  #78  
Old 07-12-2018, 06:23 PM
pkbites's Avatar
pkbites pkbites is offline
Charter Member
 
Join Date: Apr 2000
Location: Majikal Land O' Cheeze!
Posts: 10,526
I remember back in the late 60's- early 70's when I was a kid in school and the push for metrics started in the USA. I was like "you just taught me inches, feet, pounds, etc, now you're telling me to forget that and do this?" So, yeah, I was resistant. But when I got older I realized our system is based on nothing and doesn't really make any sense.

what's really messed up is Puerto Rico. Speed limit signs in MPH, distance signs in KM. WTF?
__________________
I got tired of coming up with last-minute desperate solutions to impossible problems created by other fucking people!

William Stranix

Last edited by pkbites; 07-12-2018 at 06:24 PM.
  #79  
Old 07-12-2018, 06:34 PM
Lemur866's Avatar
Lemur866 Lemur866 is online now
Charter Member
 
Join Date: Jul 2000
Location: The Middle of Puget Sound
Posts: 22,199
Quote:
Originally Posted by rat avatar View Post
A cite, from a book that most people interested in this area probably have access to.

A demonstration on why algebraic properties of floating point are neither associative nor distributive can be found in section 4.2.2 of:

The Art of Computer Programming; Volume 2, Seminumerical Algorithms. - Knuth D. (1969)
Agreed that doing operations on floating point values can give you trouble if you're not careful, and when you start with X and divide by Y and then multiply by Y you might not end up with X again, but another number that's close to X but not exactly the same.

What does that have to do with the metric system? The fact that there is no exact representation for 1/10th in binary? How exactly does it make doing operations on metric measurements harder?

Again, dividing a meter into 10 parts doesn't give an exact representation in binary. Dividing a foot into 10 parts doesn't either. Dividing a foot into 12 parts doesn't either, and neither does dividing a meter into 12 parts. The only fractions that have exact representations in binary are 1/2, 1/4, 1/8, 1/16, and so on. 1/12 doesn't have one.

Yes, you can represent 1/12, not as 0.00010101... but as one divided by twelve, or 1/1100, and then you've preserved your exact representation with integer values. But that's not a representation of an exact foot divided exactly into exact inches, that's a representation of one divided by twelve, and if you want to divide a meter into twelve parts you can use the exact same method. Or a meter divided into ten parts.

Last edited by Lemur866; 07-12-2018 at 06:37 PM.
  #80  
Old 07-12-2018, 06:37 PM
am77494 am77494 is offline
Guest
 
Join Date: Mar 2012
Posts: 1,350
Quote:
Originally Posted by Nava View Post
And I'm not sure what do you mean by NTP and STP. In my world those are conditions, not units, and were abandoned decades ago in favor of stating the exact temperature.
Indeed those are conditions, but they were not abandoned in the chemical Engineering world.

When you deal with gases : Hydrogen, Natural Gas, Air, Ethylene, Propylene, Oxygen, etc etc they are bought and sold in volumes not weight and their flow is measured in volumes again.

So a Natural Gas plant in the US will have a capacity of say 1 Million SCFD (Standard cubic feet per day), while the same in China (or Europe) will be 1116 NM3/hr (Normal cubic meter per hour).

Note that it is not just the volume units that need conversion but the reference temperature too. Hope this helps.
  #81  
Old 07-12-2018, 06:45 PM
Cugel Cugel is offline
Guest
 
Join Date: Jan 2003
Location: Canberra
Posts: 855
Quote:
Originally Posted by pkbites View Post
what's really messed up is Puerto Rico. Speed limit signs in MPH, distance signs in KM. WTF?
Heh, I watch a lot factual TV, some of which comes from the UK. The presenters/writers routinely mix systems in the same sentence
  #82  
Old 07-12-2018, 06:49 PM
rat avatar's Avatar
rat avatar rat avatar is online now
Member
 
Join Date: Dec 2009
Location: Seattle, Wa
Posts: 4,849
Quote:
Originally Posted by Lemur866 View Post
There is no object in the world that is exactly 4 inches long. There might be objects that are 4.0 inches long, or 4.0000 inches long. But there is no such thing as an object that is precisely 4 integer inches long, because measurements don't work that way.

Again, 4 is a perfectly legitimate number. It's my favorite integer. And when I say that I have a 4 inch chef's knife, is that chef's knife 4 integer inches long?

Of course not, because even if those knives are manufactured with unearthly precision, they are going to vary by some number of atoms, they're going to expand or contract based on temperature, and so on.

So 4 is not a precise value for the measurement of a knife. It's a value that means somewhere between 3.5 and 4.5, not something more precise than 4.000000000000000000.

And again, if you need to keep track of integer values for length for some reason, how does the fact that the knife is in inches or feet make it more precise than if it is in centimeters or meters? Yes, you can divide a foot into 12 inches. You can divide a meter into 1/12th of a meter with exactly the same ease.
I was not making that argument, but are you saying that dividing physical objects into quarters or thirds is not common? Oddly enough I am probably one of the very few Americans who uses a metric tape measure, which I have because it won't walk away with coworkers or if it does it doesn't go very far.

Remember to read up thread, where I was discussing the debasement of other systems, not saying the metric system is not very useful.

Luckily for my use case the lack of a line 3.3333333333333333... CM isn't a huge issue, but I may be reading it wrong so I just took a quick picture.

https://imgur.com/a/YSTgJgq

Is this just user error?

Accuracy: closeness of a measured value to a standard or known value
Precision: closeness of two or more measurements to each other.
Once again, for people who need to divide physical quantities in portions, have a more difficult time doing so under decimal based systems. Obviously I have no problem with the metric system but I am curious why people are so vehemently defending it when knowing the limitations of a system is also critical to precision and accuracy. Some jobs like machinists are dividing values all day long so fractions maintain both accuracy and precision as defined above.

This is a single example and I didn't choose the /3 idea, but 333 Millimeters +-1mm is the best you can get in that case, and with that tape measure. There are more factors and options with systems that chose to pick number bases with more factors.

I am not sure why this is so controversial.

Last edited by rat avatar; 07-12-2018 at 06:50 PM.
  #83  
Old 07-12-2018, 06:59 PM
beowulff's Avatar
beowulff beowulff is online now
Member
 
Join Date: May 2001
Location: Scottsdale, more-or-less
Posts: 16,018
Quote:
Originally Posted by rat avatar View Post
I was not making that argument, but are you saying that dividing physical objects into quarters or thirds is not common? Oddly enough I am probably one of the very few Americans who uses a metric tape measure, which I have because it won't walk away with coworkers or if it does it doesn't go very far.

Remember to read up thread, where I was discussing the debasement of other systems, not saying the metric system is not very useful.

Luckily for my use case the lack of a line 3.3333333333333333... CM isn't a huge issue, but I may be reading it wrong so I just took a quick picture.

https://imgur.com/a/YSTgJgq

Is this just user error?

Accuracy: closeness of a measured value to a standard or known value
Precision: closeness of two or more measurements to each other.
Once again, for people who need to divide physical quantities in portions, have a more difficult time doing so under decimal based systems. Obviously I have no problem with the metric system but I am curious why people are so vehemently defending it when knowing the limitations of a system is also critical to precision and accuracy. Some jobs like machinists are dividing values all day long so fractions maintain both accuracy and precision as defined above.

This is a single example and I didn't choose the /3 idea, but 333 Millimeters +-1mm is the best you can get in that case, and with that tape measure. There are more factors and options with systems that chose to pick number bases with more factors.

I am not sure why this is so controversial.
It's controversial because it's nonsense.
If you knew anything about machining, you would know that all modern machine tools are programmed in decimal - either millimeters or microns or decimal inches. No CNC system has a fractional scale (although, they may be able to convert factional input to decimal). I design PCB, and I can pick my layout grid as mm or inches, but everything gets converted to the nearest mil (1/1000 of an inch) when it's output.
  #84  
Old 07-12-2018, 07:04 PM
Cugel Cugel is offline
Guest
 
Join Date: Jan 2003
Location: Canberra
Posts: 855
Quote:
Originally Posted by Orwell View Post
In between, each decile has an easily observable and relatable amount of coolness or warmth. That simply doesn't happen with the C scale.

<0 freezing
0-10 cold
11-20 cool
21-30 pleasant
31-40 hot
41+ stinker

or
<0 freezing
0-5 cold
6-10 also cold
11-15 cool but bearable
16-20 cool but pleasantish
21-25 nice
26-30 warm, approaching hot if you are active.
31-35 hot
36-40 unpleasantly hot
41+ real stinker

With personal modifications depending on what you're used to, and what you're doing.
  #85  
Old 07-12-2018, 07:11 PM
scr4 scr4 is online now
Member
 
Join Date: Aug 1999
Location: Alabama
Posts: 14,941
Quote:
Originally Posted by rat avatar View Post
Once again, for people who need to divide physical quantities in portions, have a more difficult time doing so under decimal based systems. Obviously I have no problem with the metric system but I am curious why people are so vehemently defending it when knowing the limitations of a system is also critical to precision and accuracy. Some jobs like machinists are dividing values all day long so fractions maintain both accuracy and precision as defined above.

This is a single example and I didn't choose the /3 idea, but 333 Millimeters +-1mm is the best you can get in that case, and with that tape measure. There are more factors and options with systems that chose to pick number bases with more factors.

I am not sure why this is so controversial.
I still don't understand your point. If you are using a ruler and pencil to make a mark, the best you're going to get is about 0.5mm accuracy anyway. Marking 350mm exactly isn't any more accurate than 333.33mm using the same tools.

Even if we accept that dividing physical quantities into equal portions is a common operation, you only end up with an integer result in a few special cases. Why would it be more common to divide 1 foot into 3 than, say, 1 foot into 5, or 13.7 inches into 3? My American tape measure doesn't have a mark at 2.4" or 4.57".

Anyway, I review mechanical drawings all the time, and everything is in decimal inches anyway. You never see "1/2 inch" in a drawing, you see 0.500.

Last edited by scr4; 07-12-2018 at 07:14 PM.
  #86  
Old 07-12-2018, 07:17 PM
rat avatar's Avatar
rat avatar rat avatar is online now
Member
 
Join Date: Dec 2009
Location: Seattle, Wa
Posts: 4,849
Quote:
Originally Posted by beowulff View Post
It's controversial because it's nonsense.
If you knew anything about machining, you would know that all modern machine tools are programmed in decimal - either millimeters or microns or decimal inches. No CNC system has a fractional scale (although, they may be able to convert factional input to decimal). I design PCB, and I can pick my layout grid as mm or inches, but everything gets converted to the nearest mil (1/1000 of an inch) when it's output.
Your ad hominem ignores the reality that G Code directives often have to be corrected for spring, tool parameters and that for critical applications the end product has to be tested to see if it is within spec.

I am not claiming to be an expert at all but I have fought the G4* codes enough to know that job shops can't ignore variables like cutter radius compensation.

But you most likely ship your designs off to a PCB service, and the programs are working with well known footprints and designs. FYI, I built a 3 axis milling machine for mechanical etching of PCBs from scratch, used Voronoi tool-paths and could still get away with a hot plate for a L6470. Have you ever CNC etched a board for a simple solder paste using expensive chips like HTSSOP28? It is a real bummer when they don't float to the right place.

Thats why talking about the facts tends to be a better idea than ad hominems.

You don't have to worry about it because someone else is doing QA for you, and circuit boards are fairly easy to do most QC anyway with just calibrated cameras. But that has only been true for the past couple of decades and takes a lot more then traditional machinist tools. And not many applications are that simple.

Last edited by rat avatar; 07-12-2018 at 07:19 PM.
  #87  
Old 07-12-2018, 07:18 PM
Lemur866's Avatar
Lemur866 Lemur866 is online now
Charter Member
 
Join Date: Jul 2000
Location: The Middle of Puget Sound
Posts: 22,199
Quote:
Originally Posted by rat avatar View Post
This is a single example and I didn't choose the /3 idea, but 333 Millimeters +-1mm is the best you can get in that case, and with that tape measure. There are more factors and options with systems that chose to pick number bases with more factors.

I am not sure why this is so controversial.
It's controversial because you're bouncing around.

Do you stand by your assertion that traditional measures are easier to represent on computer systems? Or not?

Yes, it's a tragedy that there's no exact marker for 1/3 of a meter on a metric tape measure. There's no such exact marker on a traditional tape measure either.

If you have something that's a foot long, it's easy to divide it in half, or thirds, or fourths, or sixths, or twelfths using a traditional ruler. Just line it up and mark every six inches, or four inches, or three inches, or two inches, or one inch.

But what if the object you want to divide isn't a foot long? If it's 14 inches long?

If you have an object of arbitrary size that you want to divide closely into fractions of 1/2, 1/3, 1/4, or whatever, you aren't any better off with a traditional tape measure, because one third of 12.234 feet isn't any integer value.

Also, if you're dealing with real world objects, the preciseness with which you can measure and the preciseness with which you can cut start to overwhelm your mathematical round errors. Oh, you don't have an exact 333.33333... millimeter spot on your tape measure? Yeah, but the line that marks 4 inches on a ruler is wider than a tenth of a millimeter anyway. You can't mark precisely 4.0000 inches with a pencil, because your pencil won't make lines that small. And you can't saw at exactly 4.0000 inches because your saw blade is wider than 0.00001 inches.

If you need that much precision, you can't use a regular ruler and a pencil and a saw, you have to use better tools.
  #88  
Old 07-12-2018, 07:19 PM
bob++ bob++ is offline
Guest
 
Join Date: Jan 2013
Location: Worcestershire UK
Posts: 6,202
Quote:
Originally Posted by Cugel View Post
Heh, I watch a lot factual TV, some of which comes from the UK. The presenters/writers routinely mix systems in the same sentence
Which is how it is here. Shopping list:

1 doz eggs
4 pints milk
½ litre cooking oil
500 grams sugar
6 botts beer (330ml)

I drive 2 miles to buy 50 litres of petrol in a car that does 25mpg.

A new baby's weight will be recorded as 3.8kg and the parents told they have an 8lb 6oz baby.

Last edited by bob++; 07-12-2018 at 07:19 PM.
  #89  
Old 07-12-2018, 07:40 PM
rat avatar's Avatar
rat avatar rat avatar is online now
Member
 
Join Date: Dec 2009
Location: Seattle, Wa
Posts: 4,849
Quote:
Originally Posted by Lemur866 View Post
It's controversial because you're bouncing around.

Do you stand by your assertion that traditional measures are easier to represent on computer systems? Or not?

Yes, it's a tragedy that there's no exact marker for 1/3 of a meter on a metric tape measure. There's no such exact marker on a traditional tape measure either.

If you have something that's a foot long, it's easy to divide it in half, or thirds, or fourths, or sixths, or twelfths using a traditional ruler. Just line it up and mark every six inches, or four inches, or three inches, or two inches, or one inch.

But what if the object you want to divide isn't a foot long? If it's 14 inches long?

If you have an object of arbitrary size that you want to divide closely into fractions of 1/2, 1/3, 1/4, or whatever, you aren't any better off with a traditional tape measure, because one third of 12.234 feet isn't any integer value.

Also, if you're dealing with real world objects, the preciseness with which you can measure and the preciseness with which you can cut start to overwhelm your mathematical round errors. Oh, you don't have an exact 333.33333... millimeter spot on your tape measure? Yeah, but the line that marks 4 inches on a ruler is wider than a tenth of a millimeter anyway. You can't mark precisely 4.0000 inches with a pencil, because your pencil won't make lines that small. And you can't saw at exactly 4.0000 inches because your saw blade is wider than 0.00001 inches.

If you need that much precision, you can't use a regular ruler and a pencil and a saw, you have to use better tools.
I looked through my past posts, I am bouncing around answering straw-men reply's. Which I admit is always a bad idea.

My message has been consistent.

1) The avoirdupois pound mass, and the wine gallon are useful in some domains, and were superior previous the the industrial revolution in a context of limited technology.
2) In some domains these systems are still easier to use but that is use-case dependent.
3) In general a unified form of measurement is better and SI is the best bet.
4) Neither decimal nor factorable systems are good or bad in a black and white fashion, both have trade-offs with real implications.
5) Do not confuse the Imperial based fluid measurements, which are an artifact of British currency with the US system which was based on Queen Anne's older rules.
6) It is mildly amusing to be having this conversation using hexadecimal, when the main point everyone seems to have is that 'customary units are bad because decimal is good enough'
Added:
7) I obviously am forced to deal with massive changes in scale more then the average dope user.

Last edited by rat avatar; 07-12-2018 at 07:44 PM.
  #90  
Old 07-12-2018, 07:48 PM
beowulff's Avatar
beowulff beowulff is online now
Member
 
Join Date: May 2001
Location: Scottsdale, more-or-less
Posts: 16,018
Quote:
Originally Posted by rat avatar View Post
I looked through my past posts, I am bouncing around answering straw-men reply's. Which I admit is always a bad idea.

My message has been consistent.

1) The avoirdupois pound mass, and the wine gallon are useful in some domains, and were superior previous the the industrial revolution in a context of limited technology.
2) In some domains these systems are still easier to use but that is use-case dependent.
3) In general a unified form of measurement is better and SI is the best bet.
4) Neither decimal nor factorable systems are good or bad in a black and white fashion, both have trade-offs with real implications.
5) Do not confuse the Imperial based fluid measurements, which are an artifact of British currency with the US system which was based on Queen Anne's older rules.
6) It is mildly amusing to be having this conversation using hexadecimal, when the main point everyone seems to have is that 'customary units are bad because decimal is good enough'
Added:
7) I obviously am forced to deal with massive changes in scale more then the average dope user.
Those are all reasonable points.
So, you retract your statement which lead to all this back-and-forth:
Quote:
SI becomes problematic with computers (not SI's falt) as an example
???

Last edited by beowulff; 07-12-2018 at 07:48 PM.
  #91  
Old 07-12-2018, 08:00 PM
rat avatar's Avatar
rat avatar rat avatar is online now
Member
 
Join Date: Dec 2009
Location: Seattle, Wa
Posts: 4,849
Quote:
Originally Posted by beowulff View Post
Those are all reasonable points.
So, you retract your statement which lead to all this back-and-forth:
???
Nope, see points #4, #6 and #7


I hope that the decimal floating-point unit of IBM's POWER cpus takes off, but as half precision is faster and good enough for sigmoid funcitons in ML I doubt it will. decimal128 may be in IEEE 754-2008 but I'll have to deal with relativity poor performing software implementations for now.

Feel free to provide a cite that I am in error about a large portion decimals haveing infinite representations in binary, and division by powers of 10 is one of them. I provided a cite, but for my current needs I can't even use the entire mantissa in the 8087 era FPUs because I have to avoid the count by two change in the binary number line too.

I will not concede that FP doesn't have it's very well known problems, including numbers that do not exist in binary like .1, .01 ... without evidence.

Last edited by rat avatar; 07-12-2018 at 08:04 PM.
  #92  
Old 07-12-2018, 08:37 PM
beowulff's Avatar
beowulff beowulff is online now
Member
 
Join Date: May 2001
Location: Scottsdale, more-or-less
Posts: 16,018
Quote:
Originally Posted by rat avatar View Post
Nope, see points #4, #6 and #7


I hope that the decimal floating-point unit of IBM's POWER cpus takes off, but as half precision is faster and good enough for sigmoid funcitons in ML I doubt it will. decimal128 may be in IEEE 754-2008 but I'll have to deal with relativity poor performing software implementations for now.

Feel free to provide a cite that I am in error about a large portion decimals haveing infinite representations in binary, and division by powers of 10 is one of them. I provided a cite, but for my current needs I can't even use the entire mantissa in the 8087 era FPUs because I have to avoid the count by two change in the binary number line too.

I will not concede that FP doesn't have it's very well known problems, including numbers that do not exist in binary like .1, .01 ... without evidence.
Please, just answer one question - what makes this precision problem worse for the metric system?
  #93  
Old 07-12-2018, 08:45 PM
rat avatar's Avatar
rat avatar rat avatar is online now
Member
 
Join Date: Dec 2009
Location: Seattle, Wa
Posts: 4,849
I finally found the term 'dyadic rational' deep down in the recesses of my grey matter, and the first google hit is Wikipedia of course. Which while always a questionable source due to their desire to simplify over accuracy has the most accessible description I can find.

https://en.wikipedia.org/wiki/Dyadic_rational

Note the image on the top of the page, and how it looks exactly like a USC ruler or tape measure, then note this statement in the opening block.

Quote:
These are precisely the numbers whose binary expansion is finite.
And the statement on use in measurement

Quote:
The inch is customarily subdivided in dyadic rather than decimal fractions; similarly, the customary divisions of the gallon into half-gallons, quarts, and pints are dyadic. The ancient Egyptians also used dyadic fractions in measurement, with denominators up to 64.
Hopefully this will help explain why I am having what seems like a debate in GQ.

Dyadic rationals are finite in floating point because floating point is made up of dyadic rationals. You still have problems with the epsilon, small values and large values but USC units are less impacted by cumulative FP errors in computers due to the very structure.

My claims are not made as an opinion, and I apologize for failing to remember the correct term.
  #94  
Old 07-12-2018, 08:51 PM
rat avatar's Avatar
rat avatar rat avatar is online now
Member
 
Join Date: Dec 2009
Location: Seattle, Wa
Posts: 4,849
Quote:
Originally Posted by beowulff View Post
Please, just answer one question - what makes this precision problem worse for the metric system?
As I didn't see this post with my last reply,

Addition, multiplication and subtraction of dyadic fractions always results in another dyadic fraction. And while division doesn't always end up being a dyadic fraction it is far more likely to do so then decimal to floating point.

Customary units are dyadic and floating point is dyadic and many numbers that are finite in decimal representations are not finite in dyadic form so you have rounding and representation errors.

UTF8 doesn't have good symbols for set theory and the dope doesn't support mathtex or other tools that would help so....

∴ math

Last edited by rat avatar; 07-12-2018 at 08:53 PM. Reason: Had to do at least one math char
  #95  
Old 07-12-2018, 09:16 PM
DavidwithanR DavidwithanR is offline
BANNED
 
Join Date: Feb 2018
Posts: 3,996
Quote:
Originally Posted by Orwell View Post
Exactly. I would have no problem with the metric system for lengths, weights and volumes, and would actually prefer it for some applications like wrenches and kitchen measurements. But not temperature. Yeah, I get the scientific rationale for 0=freezing and 100=boiling, but that means little in everyday life as we live it. Fahrenheit is much more intuitive and useful for weather and indoor and outdoor temps.
There is absolutely nothing intuitive about Fahrenheit or any other temperature scale. Nothing. You're just used to it - it really is that simple.

I just invented the one and only truly intuitive temperature scale. Comfortable is zero. Way too hot is +10; way too cold is -10. THAT'S intuitive. (And basically useless.)
  #96  
Old 07-12-2018, 09:21 PM
Isamu Isamu is offline
Guest
 
Join Date: Aug 2007
Location: Osaka
Posts: 5,841
Quote:
Originally Posted by Surreal View Post
Wrong. People prefer to use units of measurement that they're already familiar with, and the only real advantage of SI units is that the conversion factors (10X, 1000X, etc.) are simpler if you don't have access to a computer.
Wrong. Show me one person educated in a metric system who is an advocate for change to inches.
  #97  
Old 07-12-2018, 11:01 PM
beowulff's Avatar
beowulff beowulff is online now
Member
 
Join Date: May 2001
Location: Scottsdale, more-or-less
Posts: 16,018
Quote:
Originally Posted by rat avatar View Post
I finally found the term 'dyadic rational' deep down in the recesses of my grey matter, and the first google hit is Wikipedia of course. Which while always a questionable source due to their desire to simplify over accuracy has the most accessible description I can find.

https://en.wikipedia.org/wiki/Dyadic_rational

Note the image on the top of the page, and how it looks exactly like a USC ruler or tape measure, then note this statement in the opening block.



And the statement on use in measurement



Hopefully this will help explain why I am having what seems like a debate in GQ.

Dyadic rationals are finite in floating point because floating point is made up of dyadic rationals. You still have problems with the epsilon, small values and large values but USC units are less impacted by cumulative FP errors in computers due to the very structure.

My claims are not made as an opinion, and I apologize for failing to remember the correct term.
Yeah, that's all well and good in La La land, but I would like you to give me one (1) example where a change to a different measurement system was required to cope with the disastrous loss of precision in a computer program caused by the metric system.
  #98  
Old 07-12-2018, 11:02 PM
Lemur866's Avatar
Lemur866 Lemur866 is online now
Charter Member
 
Join Date: Jul 2000
Location: The Middle of Puget Sound
Posts: 22,199
I still don't understand why it is easier to represent traditional measures using computers compared to metric measures.

Hint: you can have half a meter and it is represented in binary as 0.1. Same as half a foot. Yes, it is true that there is no traditional name for the half meter, but there's no traditional name for half a mile, or half a furlong. OK, we could call half a foot six inches instead. But if you're calculating using a computer algorithm and switching back and forth between feet and inches, you're doing it wrong.
  #99  
Old 07-12-2018, 11:09 PM
Kiwi Fruit's Avatar
Kiwi Fruit Kiwi Fruit is offline
Charter Member
 
Join Date: Apr 2003
Location: Hamilton, NZ, Male
Posts: 778
Quote:
Originally Posted by bob++ View Post
Which is how it is here. Shopping list:

1 doz eggs
4 pints milk
½ litre cooking oil
500 grams sugar
6 botts beer (330ml)

I drive 2 miles to buy 50 litres of petrol in a car that does 25mpg.

A new baby's weight will be recorded as 3.8kg and the parents told they have an 8lb 6oz baby.
That is Britain's not very sincere attempt to use metric measurements. My shopping list for the same things would be:

1 doz eggs (but some packs are in tens rather than dozens)
2 or 3 litres of milk (probably 2 as that is a standard size container)
500 ml cooking oil
500 grams sugar
6 stubbies of beer (330 or maybe 355 ml)

I drive 3 km to buy 50 litres of diesel in a car that does 6 l/100km.

The baby's weight thing repeats here though. Official weight might be 3800 gm but all parents seem to say the lbs and ozs thing. Weird as nothing else is measured in lbs/ozs so how do you do the comparison? Only to every other baby, I suppose.

I weigh myself in kg, even though my scales can be switched between that, lbs, and stones/pounds, and I grew up using stones and pounds.

Temperatures are always Celsius. Today is in the mid-teens, yesterday was in the low teens. Summer is low to mid twenties, sometimes high twenties. In a way, that is a narrower range than the deciles used in Fahrenheit.
  #100  
Old 07-12-2018, 11:58 PM
rat avatar's Avatar
rat avatar rat avatar is online now
Member
 
Join Date: Dec 2009
Location: Seattle, Wa
Posts: 4,849
Quote:
Originally Posted by beowulff View Post
Yeah, that's all well and good in La La land, but I would like you to give me one (1) example where a change to a different measurement system was required to cope with the disastrous loss of precision in a computer program caused by the metric system.
Strawman, but I already offered a few cases where ignoring this very real math problem causes issues.

Including

Stock market crashes:

https://www5.in.tum.de/~huckle/Vancouv.pdf

Rocket crashes due to casting a dyadic float to an int

http://www-users.math.umn.edu/~arnol...rs/ariane.html

Or the failure of patriot missiles to hit it's target due to the binary expansion of 1/10 that is the same issue.

http://www-users.math.umn.edu/~arnol...skeel-siam.pdf

Quote:
A 24-bit representation of 0.1 was used to multiply the clocktime,
yielding a result in a pair of 24-bit registers.

Here is another example where a very popular python package numpy, has a test using the software Decimal implementation because of the implications for financial transactions (same decimal vs float problem)

https://github.com/numpy/numpy/blob/...t_financial.py

You can also do a google search for: "What Every Computer Scientist Should Know About Floating-Point Arithmetic, by David Goldberg"

https://docs.oracle.com/cd/E19957-01..._goldberg.html

Quote:
Floating-point representations have a base (which is always assumed to be even) and a precision p. If = 10 and p = 3, then the number 0.1 is represented as 1.00 × 10-1. If = 2 and p = 24, then the decimal number 0.1 cannot be represented exactly, but is approximately 1.10011001100110011001101 × 2-4.
That paper is pretty much the "here let me google that for you" answer to the huge number of stack exchange questions that come in about the problem.

As you are an expert, or at least your ad hominem claimed before, it is worth your time understanding this just in case. Eagle, Proteus ,or Altium Designer or what ever you use will take care of it where tolerances matter like standard footprints, but it is important if you also write code.

But it is less likely in your case, DIP packages were spaced at 2.54mm because they were originally 0.1". The choice of 2.54cm == 1 inch was intentional due to the need to consider dyadic issues. Even the choices of ball pitch on BGA is intentional thus 0.40, 0.50, 0.65, 0.75, 0.80, 1.00mm. At 1mm, where there may be errors the size of panels at manufactures limits the impact, and for the smaller sizes they chose values on purpose that wouldn't lead to issues.

0.65/100 will be ~0.006500000000000001 as an example but even 0.65/100000 which is bigger then you have to worry about is ~6.5000000000000004e-06.

Be glad you are in an industry where you don't have to deal with this, it is not an easy problem to deal with. I guess you may work with UHF needs, but even with 100-µm conductor line the critical dimensions tend to deal more with the relative error, and routing will typically push out dimensions more based on bigger issues like min distances manufacturing tolerances etc. Meaning that the hard parts like via placement is relative and the error won't accumulate like with banking errors or missile trajectories. As the scale of panelization is typically limited by panel size of the manufacture it is just something you can ignore as long as the vias are where they need to be and the pick and place can get close enough.

Not all needs are as lucky.

Last edited by rat avatar; 07-13-2018 at 12:02 AM.
Reply

Bookmarks

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is Off
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 11:40 AM.

Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2018, vBulletin Solutions, Inc.

Send questions for Cecil Adams to: cecil@straightdope.com

Send comments about this website to: webmaster@straightdope.com

Terms of Use / Privacy Policy

Advertise on the Straight Dope!
(Your direct line to thousands of the smartest, hippest people on the planet, plus a few total dipsticks.)

Copyright © 2018 STM Reader, LLC.

 
Copyright © 2017