Author: Tom Likens
Date: 20:35:51 09/28/02
Go up one level in this thread
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. 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. 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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