Author: Robert Hyatt
Date: 20:34:16 09/29/02
Go up one level in this thread
On September 28, 2002 at 23:35:51, Tom Likens wrote: >On September 28, 2002 at 12:32:41, Robert Hyatt wrote: > >>On September 28, 2002 at 11:12:29, Tom Likens wrote: >> >>>On September 27, 2002 at 23:37:43, Robert Hyatt wrote: >>> >>>[snip!] >>> >>>>>>>So reality is that the above result in reality is even more positive for >>>>>>>AMD than it looks like. We simply cannot trust these intel c++ compiles. >>>>>> >>>>>>Sure you can. I have tested the 6.0 release of their compiler exhaustively, >>>>>>comparing various optimizations with a known good executable from gcc 2.95.2, >>>>>>and the intel compiler is producing perfect code from a comparison of the >>>>>>two... >>> >>>Actually, in my tests it's producing *significantly* faster code (especially, if >>>you use the profile-enabled optimizations). >>> >>>regards, >>>--tom >> >>I hope I had said the intel compiler was faster. However, Vincent keeps saying >>it produces bad code that doesn't work. I think he just writes bad code himself >>and then complains when the compiler does something that is unexpected, even >>if it is legal. I use the intel compiler everywhere, including my cluster where >>several have carefully compared program output between intel and gcc to check >>for correctness. >> >>Intel is faster and correct, which is all I want. :) > >I haven't seen any incorrect code being produced with the 6.x compiler series. >My engine is written in C++ and it stresses most compilers fairly hard (it >breaks >BoundsChecker completely when I compile it under Windows). So far, the output >of the Intel version has matched the gcc version exactly (except for the speed). > >It's possible that Vincent is using (and counting on the behavior of) some >of the compiler specific functions such as rand(). If so, even with the same >initial >seed he would get different results, which he may consider an error. I don't think that is his problem. He posted some floating point code that he claimed Intel broke. I tried it and it worked perfectly, so I can't comment on what he is doing. Perhaps it is broken when run on an AMD processor, I don't know. But I do know it is working perfectly on the 6.x Intel compilers using Intel hardware. > >On the other hand, I'm willing to give Vincent the benefit of the doubt. If he >has >a code snippet or two that he would be willing to post, that produces incorrrect >code >under the Intel compiler, I would be interested in seeing it. He posted a couple already and I tried them. They worked just fine on intel. > >Vincent? > >And yes, fast *and* correct is the goal. So far, the Intel compiler has been >impressive. >One of the more pleasant surprises was the compatability with gcc. Even the gcc >inline assembly routines I threw at it (which use AT&T syntax), compiled >correctly >the first time out of the box. I've always been, and still am, very loyal to >gcc. But >having a second quality compiler under Linux is an embarrasment of riches. >Compiling my code under both compilers keeps it (and me) "honest". > >regards, >--tom
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