5 ms·

Note that this "rant" is by Velvel Kahan [1], who won the Turing Award for designing the IEEE 754 floating point standard [2] (among other things), which is use

by ubasu 13y ago

Note that this "rant" is by Velvel Kahan [1], who won the Turing Award for designing the IEEE 754 floating point standard [2] (among other things), which is used for specifying floating point computations on almost all computers today. So perhaps he has a little more context on this than yourself. [1] http://en.wikipedia.org/wiki/William_Kahan http://en.wikipedia.org/wiki/William_Kahan [2] http://en.wikipedia.org/wiki/IEEE_754-2008 http://en.wikipedia.org/wiki/IEEE_754-2008

kefka 13y ago
But that sounds like an argument to appeal by authority. Firstly, the title page says "presented March 1, 1998". That's pretty old. And then the PDF shows creation date 'July 30, 2004'. I'll assume that there were 6 years of updates to this file between the 2 dates. So that still is about 10 years old document. How have things changed since then?
- pavpanchekha 13y ago
  Appeal to authority? Ah, I think you misunderstand why that is considered an invalid form of argument. An appeal to authority occurs when one appeals to an authority in an unrelated field in order to bolster an argument from a different field. For example, while watching football yesterday, I saw a commercial where a football player told me that CenturyLink had the fastest internet. This is an implicit appeal to authority. The player is undoubtedly an authority on how to play football, but this authority is unrelated to the question of choosing a good internet service. On the other hand, if this player were to tell me which football video games were most realistic, this would not be an invalid form of argument, since he in fact has some authority on what makes a football video game realistic (Of course, there may be higher authorities yet). In this case, William Kahan actually has authority on the proper use of floating point, as the designer of IEEE 754 and a well-known authority in numerical analysis. His credentials in programming language design, granted, are weaker, but you cannot deny that his authority does in fact extend to the object of our discussion.
  - scott_s 13y ago
    His credentials, however, do not make his argument correct.
pcwalton 13y ago
I'm not questioning the author's credentials, nor do I even think he's wrong about what's most useful in his field (scientific computing). I just think that programming language design considerations (not wanting to admit implicit conversions) outweigh his objections.
- deleted 13y ago
  [deleted]
- acqq 13y ago
  If you claim that Java was right to implement that so and the next language who ignores his complaints is also, then just accept that both Java and the next language have weaknesses expressing the computational tasks, from the point of view of the people who do have to write that kind of code. Note that for a very long time Windows didn't use FPU at all. They also "didn't need it." And I think they started to think differently once they looked enough what Apple does. A lot can be programmed without FPU, but the edge in the industry is gained by using the hardware fully. Not doing what's easiest. And the FPU hardware doesn't introduce penalties when reading 32-bit values and doing 64-bit computations.
  - pcwalton 13y ago
    That example is not comparable. The issue is not whether something is expressible. All 32-bit and 64-bit arithmetic operations are expressible in both C and Java (although I'd argue that Java makes it easier to know which you're getting). The issue is just what the default should be, and whether introducing temporaries should change the value of an expression. This is impossible to measure objectively, because we're talking formally about the exact same set of operations, just about which default is more intuitive/convenient/leading to fewer bugs/etc.
    - acqq 13y ago
      I don't agree that it's "impossible to measure objectively." The practice to store floating values with less bits but calculate with more is very old, specifically, older than C. It's not accidental, it survived because it's needed. As long as we don't have infinite memory and want to have huge inputs and outputs we'll need 32-bit floats. And as long we want to calculate with less error, and we need it, we'll need doubles as intermediate calculations.

by ubasu 13y ago

kefka 13y ago

But that sounds like an argument to appeal by authority. Firstly, the title page says "presented March 1, 1998". That's pretty old. And then the PDF shows creation date 'July 30, 2004'. I'll assume that there were 6 years of updates to this file between the 2 dates. So that still is about 10 years old document. How have things changed since then?

pavpanchekha 13y ago
Appeal to authority? Ah, I think you misunderstand why that is considered an invalid form of argument. An appeal to authority occurs when one appeals to an authority in an unrelated field in order to bolster an argument from a different field. For example, while watching football yesterday, I saw a commercial where a football player told me that CenturyLink had the fastest internet. This is an implicit appeal to authority. The player is undoubtedly an authority on how to play football, but this authority is unrelated to the question of choosing a good internet service. On the other hand, if this player were to tell me which football video games were most realistic, this would not be an invalid form of argument, since he in fact has some authority on what makes a football video game realistic (Of course, there may be higher authorities yet). In this case, William Kahan actually has authority on the proper use of floating point, as the designer of IEEE 754 and a well-known authority in numerical analysis. His credentials in programming language design, granted, are weaker, but you cannot deny that his authority does in fact extend to the object of our discussion.
- scott_s 13y ago
  His credentials, however, do not make his argument correct.

pcwalton 13y ago

I'm not questioning the author's credentials, nor do I even think he's wrong about what's most useful in his field (scientific computing). I just think that programming language design considerations (not wanting to admit implicit conversions) outweigh his objections.

deleted 13y ago
[deleted]
acqq 13y ago
If you claim that Java was right to implement that so and the next language who ignores his complaints is also, then just accept that both Java and the next language have weaknesses expressing the computational tasks, from the point of view of the people who do have to write that kind of code. Note that for a very long time Windows didn't use FPU at all. They also "didn't need it." And I think they started to think differently once they looked enough what Apple does. A lot can be programmed without FPU, but the edge in the industry is gained by using the hardware fully. Not doing what's easiest. And the FPU hardware doesn't introduce penalties when reading 32-bit values and doing 64-bit computations.
- pcwalton 13y ago
  That example is not comparable. The issue is not whether something is expressible. All 32-bit and 64-bit arithmetic operations are expressible in both C and Java (although I'd argue that Java makes it easier to know which you're getting). The issue is just what the default should be, and whether introducing temporaries should change the value of an expression. This is impossible to measure objectively, because we're talking formally about the exact same set of operations, just about which default is more intuitive/convenient/leading to fewer bugs/etc.
  - acqq 13y ago
    I don't agree that it's "impossible to measure objectively." The practice to store floating values with less bits but calculate with more is very old, specifically, older than C. It's not accidental, it survived because it's needed. As long as we don't have infinite memory and want to have huge inputs and outputs we'll need 32-bit floats. And as long we want to calculate with less error, and we need it, we'll need doubles as intermediate calculations.