Search found 692 matches

by rbarreira
Thu Dec 12, 2013 7:36 am
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: How could a compiler break the lockless hashing method?
Replies: 312
Views: 33757

Re: How could a compiler break the lockless hashing method?

I don't believe the compiler writers would bother to do this stuff if it didn't actually speed up some actual programs out there. Their job is to generate the best possible code while complying with the spec. Our job is to write programs, but if we want those programs to work reliably, we also have...
by rbarreira
Wed Dec 11, 2013 6:42 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: How could a compiler break the lockless hashing method?
Replies: 312
Views: 33757

Re: How could a compiler break the lockless hashing method?

I don't believe the compiler writers would bother to do this stuff if it didn't actually speed up some actual programs out there. Their job is to generate the best possible code while complying with the spec. Our job is to write programs, but if we want those programs to work reliably, we also have...
by rbarreira
Wed Dec 11, 2013 6:29 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: How could a compiler break the lockless hashing method?
Replies: 312
Views: 33757

Re: How could a compiler break the lockless hashing method?

What I am asking of the compiler is "get out of the way and let the hardware do what it will do." Don't try to make assumptions. That is not a reasonable request of you, because not only is there different hardware out there but even on x86 there are many different ways to calculate "x * 2": - the ...
by rbarreira
Wed Dec 11, 2013 5:25 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: How could a compiler break the lockless hashing method?
Replies: 312
Views: 33757

Re: How could a compiler break the lockless hashing method?

Sorry you feel that way. I simply have my opinion, developed over several years of compiler development. Objection, facts not in evidence. Please show us which conforming C compiler you actually developed? Or any other compiler that was used by anyone except yourself, your students or coworkers. Di...
by rbarreira
Wed Dec 11, 2013 5:23 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: How could a compiler break the lockless hashing method?
Replies: 312
Views: 33757

Re: How could a compiler break the lockless hashing method?

No. You just refuse to read. Use the best math available on the cpu, and let overflow happen when it must. But that is exactly what the compilers try to do. They use the "best math" (in which best is usually dictated by performance and not some irrelevant notion of "best" which can still give diffe...
by rbarreira
Wed Dec 11, 2013 5:05 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: How could a compiler break the lockless hashing method?
Replies: 312
Views: 33757

Re: How could a compiler break the lockless hashing method?

But all I get back is "but it is undefined behavior according to the standard." Well, this discussion can of course never come to a conclusion, because there are two camps that argue from different underlying axioms. On the one side there are people that take it for granted that "Standards are ther...
by rbarreira
Wed Dec 11, 2013 4:44 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: How could a compiler break the lockless hashing method?
Replies: 312
Views: 33757

Re: How could a compiler break the lockless hashing method?

What I am asking of the compiler is "get out of the way and let the hardware do what it will do." Don't try to make assumptions. That is not a reasonable request of you, because not only is there different hardware out there but even on x86 there are many different ways to calculate "x * 2": - the ...
by rbarreira
Wed Dec 11, 2013 4:41 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: How could a compiler break the lockless hashing method?
Replies: 312
Views: 33757

Re: How could a compiler break the lockless hashing method?

Sorry you feel that way. I simply have my opinion, developed over several years of compiler development. Objection, facts not in evidence. Please show us which conforming C compiler you actually developed? Or any other compiler that was used by anyone except yourself, your students or coworkers. Di...
by rbarreira
Wed Dec 11, 2013 4:35 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: How could a compiler break the lockless hashing method?
Replies: 312
Views: 33757

Re: How could a compiler break the lockless hashing method?

I don't believe the compiler writers would bother to do this stuff if it didn't actually speed up some actual programs out there. Their job is to generate the best possible code while complying with the spec. Our job is to write programs, but if we want those programs to work reliably, we also have...
by rbarreira
Wed Dec 11, 2013 4:23 pm
Forum: Computer Chess Club: Programming and Technical Discussions
Topic: How could a compiler break the lockless hashing method?
Replies: 312
Views: 33757

Re: How could a compiler break the lockless hashing method?

What I am asking of the compiler is "get out of the way and let the hardware do what it will do." Don't try to make assumptions. That is not a reasonable request of you, because not only is there different hardware out there but even on x86 there are many different ways to calculate "x * 2": - the ...