4 ms·

Memory capacity and commercial compiler development

30 points by johndcook 15y ago

cwzwarich 15y ago
I am not sure I totally get the author's point. Many commercial compilers had already implemented and shipped many of the optimizations later found in GCC before GCC did, although these compilers were often for a different class of machine than the average desktop Linux PC. Is he saying that GCC implemented them just as they became viable on lower end hardware?
- derleth 15y ago
  > Is he saying that GCC implemented them just as they became viable on lower end hardware? To begin with, gcc didn't target low-end hardware; low-end hardware of 1985 (the beginning of the GNU Project) wasn't capable of running serious OSes, so Stallman ignored it in favor of workstations built around Motorola 68000 CPUs (I believe). But that's beside the point: He's saying that once lower-end systems began to be as capable of the optimizations as high-end systems were previously, the expectations of compilers for low-end systems began to match the expectations of compilers for high-end systems. He's also implicitly making the point that, once CPU speed is above a certain minimum, the thing that most limits a computer is a shortage of RAM. A compiler for an MS-DOS system with a few hundred K of RAM can't do advanced register scheduling (not that the 8088 has a lot of registers to begin with) or code transformations but that's OK, because nobody expects it to. All people expect is for their Borland Pascal or Pacific C or whatever compiler to emit machine code that correctly implements their algorithm and, if it's a bit slow, they'll grab Ralf Brown's Interrupt List and other reference material and start hacking assembly. In Linux, in 2011, people expect gcc to not only correctly unroll loops, but to transform recursive functions into an iterative form and then unroll the resulting loop. (gcc can, actually, do this.) They expect gcc to use MMX opcodes in somewhat-ingenious ways to speed up string handling; and as an aside most of the more interesting opcodes of the x86 ISA are another thing the solo MS-DOS hackers didn't have to worry much about until near the end of the MS-DOS era. They expect, in short, a compiler that would have been at home on a very high-end system as recently as the early 1990s and is therefore too complex for any single human to write unaided. (Well, perhaps Knuth could, but Knuth doesn't scale.)
mathattack 15y ago
Interesting. Seems like a rare instance of increased computing power hurting individual programmer productivity. Then again increased computing power in general enables more complex software with more specializes software. I have heard that Safari is the product of a very small team, but that's the exception.
- ars 15y ago
  It has not hurt the productivity - it's just now more productivity is expected. The individual productivity is probably higher than before, but the need (or expectation) is even higher than that.
  - mathattack 15y ago
    You said what I meant to say, but much more concisely, or dare I say productively? :-)
shaggyfrog 15y ago
> When I started out in the compiler business in the 80s many commercial compilers were originally written by one person. A very good person who dedicated himself (I have never heard of a woman doing this) Grace Hopper?
- naz 15y ago
  I too found that side-note a bit unnecessary. "Himself" works just fine as a gender-neutral pronoun.
- deleted 15y ago
  [deleted]
- kragen 15y ago
  Not to mention Betty Snyder Holberton, Adele Mildred "Millie" Coss, and I think Jean Sammet. You can probably add Elizabeth Rather to the list; although she was the head of a company at the time, I'm sure there are commercial compilers from the company that she wrote singlehandedly. She also has the distinction of having done this during the 1980s, when the bar for a compiler was a lot higher.
- derleth 15y ago
  Did any of Grace Hopper's work get released commercially? She was an admiral in the Navy, after all.
  - shaggyfrog 15y ago
    Is that really the point, though? kragen's sibling post makes a better case.
kenjackson 15y ago
The author is generally right. But it's not unique to compilers. Many things were often written by just one person in the early days, but rarely so now. PC and console games, for example, were often written by one person. Now of course there are huge studios that do it (although mobile games can now be written by one person). Programs have seen an explosion in feature set. For compilers this feature set includes optimzation, and additionally things like AutoComplete/IntelliSense, debug information, precompiled headers, etc... With that said optimization probably dominates, in terms of headcount, what most compiler devs work on.
derleth 15y ago
It's also no longer the case that a single person can build a commercially competitive automobile or airplane. Even ignoring all the relevant regulations, most people buying those things expect features like anti-lock breaking and navigation systems and wings that are not made out of canvas stretched across cunningly-bent pieces of wood. On the other hand, a modern kit car would make the young Karl Benz green with envy. A modern kit airplane would make the Wright brothers... well, they were pretty emotionally reserved, but I think I can safely say they would be intensely interested in every single aspect. I think the main part he leaves out is that not only do we have better, more complex tools, we have better, more complex tools to build tools. The continuing expansion of expectations is only natural given our continuing expansion of capacity.
beagle3 15y ago
And yet, Mike Pall singlehandedly wrote LuaJit2 which is, by far, the best ever compiler for a dynamic language. None other comes close at this time.

30 points by johndcook 15y ago

I am not sure I totally get the author's point. Many commercial compilers had already implemented and shipped many of the optimizations later found in GCC before GCC did, although these compilers were often for a different class of machine than the average desktop Linux PC. Is he saying that GCC implemented them just as they became viable on lower end hardware?

derleth 15y ago
> Is he saying that GCC implemented them just as they became viable on lower end hardware? To begin with, gcc didn't target low-end hardware; low-end hardware of 1985 (the beginning of the GNU Project) wasn't capable of running serious OSes, so Stallman ignored it in favor of workstations built around Motorola 68000 CPUs (I believe). But that's beside the point: He's saying that once lower-end systems began to be as capable of the optimizations as high-end systems were previously, the expectations of compilers for low-end systems began to match the expectations of compilers for high-end systems. He's also implicitly making the point that, once CPU speed is above a certain minimum, the thing that most limits a computer is a shortage of RAM. A compiler for an MS-DOS system with a few hundred K of RAM can't do advanced register scheduling (not that the 8088 has a lot of registers to begin with) or code transformations but that's OK, because nobody expects it to. All people expect is for their Borland Pascal or Pacific C or whatever compiler to emit machine code that correctly implements their algorithm and, if it's a bit slow, they'll grab Ralf Brown's Interrupt List and other reference material and start hacking assembly. In Linux, in 2011, people expect gcc to not only correctly unroll loops, but to transform recursive functions into an iterative form and then unroll the resulting loop. (gcc can, actually, do this.) They expect gcc to use MMX opcodes in somewhat-ingenious ways to speed up string handling; and as an aside most of the more interesting opcodes of the x86 ISA are another thing the solo MS-DOS hackers didn't have to worry much about until near the end of the MS-DOS era. They expect, in short, a compiler that would have been at home on a very high-end system as recently as the early 1990s and is therefore too complex for any single human to write unaided. (Well, perhaps Knuth could, but Knuth doesn't scale.)

mathattack 15y ago

Interesting. Seems like a rare instance of increased computing power hurting individual programmer productivity. Then again increased computing power in general enables more complex software with more specializes software. I have heard that Safari is the product of a very small team, but that's the exception.

ars 15y ago
It has not hurt the productivity - it's just now more productivity is expected. The individual productivity is probably higher than before, but the need (or expectation) is even higher than that.
- mathattack 15y ago
  You said what I meant to say, but much more concisely, or dare I say productively? :-)

shaggyfrog 15y ago

> When I started out in the compiler business in the 80s many commercial compilers were originally written by one person. A very good person who dedicated himself (I have never heard of a woman doing this) Grace Hopper?

naz 15y ago
I too found that side-note a bit unnecessary. "Himself" works just fine as a gender-neutral pronoun.
deleted 15y ago
[deleted]
kragen 15y ago
Not to mention Betty Snyder Holberton, Adele Mildred "Millie" Coss, and I think Jean Sammet. You can probably add Elizabeth Rather to the list; although she was the head of a company at the time, I'm sure there are commercial compilers from the company that she wrote singlehandedly. She also has the distinction of having done this during the 1980s, when the bar for a compiler was a lot higher.
derleth 15y ago
Did any of Grace Hopper's work get released commercially? She was an admiral in the Navy, after all.
- shaggyfrog 15y ago
  Is that really the point, though? kragen's sibling post makes a better case.

kenjackson 15y ago

The author is generally right. But it's not unique to compilers. Many things were often written by just one person in the early days, but rarely so now. PC and console games, for example, were often written by one person. Now of course there are huge studios that do it (although mobile games can now be written by one person). Programs have seen an explosion in feature set. For compilers this feature set includes optimzation, and additionally things like AutoComplete/IntelliSense, debug information, precompiled headers, etc... With that said optimization probably dominates, in terms of headcount, what most compiler devs work on.

derleth 15y ago

It's also no longer the case that a single person can build a commercially competitive automobile or airplane. Even ignoring all the relevant regulations, most people buying those things expect features like anti-lock breaking and navigation systems and wings that are not made out of canvas stretched across cunningly-bent pieces of wood. On the other hand, a modern kit car would make the young Karl Benz green with envy. A modern kit airplane would make the Wright brothers... well, they were pretty emotionally reserved, but I think I can safely say they would be intensely interested in every single aspect. I think the main part he leaves out is that not only do we have better, more complex tools, we have better, more complex tools to build tools. The continuing expansion of expectations is only natural given our continuing expansion of capacity.

beagle3 15y ago

And yet, Mike Pall singlehandedly wrote LuaJit2 which is, by far, the best ever compiler for a dynamic language. None other comes close at this time.