problem with gcc 4.2 produced OpenMP code
problem with gcc 4.2 produced OpenMP code
- Subject: problem with gcc 4.2 produced OpenMP code
- From: Chinh Nguyen <email@hidden>
- Date: Fri, 17 Oct 2008 10:28:01 -0500
We have an MP version of our app on all platforms using OpenMP. We
currently use icc to build the 32-bit Carbon MP version. I was
interested in using gcc 4.2 to compile the MP version of our app
because it would allow me to continue mixing objective-c code in our c
code without resorting to writing wrappers. This makes porting from
Carbon to Cocoa easier (I'm currently compiling all the c source files
with the objective-c compiler in our Cocoa build). After successfully
building a 32-bit Cocoa MP version of our app with gcc 4.2, I ran our
test suite so I could compare timings between the icc and gcc 4.2
builds. The gcc 4.2 produced build didn't even pass certification
(the icc version does). The app doesn't crash... it just hangs. It's
stuck in an infinite loop but when we pause it with the debugger,
we're staring at OpenMP's library assembler code so we can't tell what
the problem is.
FWIW, the icc version will only pass our test suite when we use the -
fp precise option (it defaults to fast). I couldn't find any similar
option with gcc but I'm not sure accuracy is the problem because the
fast option with icc doesn't hang our app, it just doesn't provide the
accuracy our app requires. The point may be moot because I think icc
produced code is faster than gcc produced code but I just want to
confirm it.
PS. I was able to build a 64-bit MP Cocoa version of our app using
gcc 4.0 and icc (but using Xcode 3.0 -- see earlier email about
building 64-bit app). That took some serious finagling in Xcode but
it works which is awesome. I thought I was going to have to resort to
make scripts. However, I still can't build the 64-bit MP Cocoa
version with Xcode 3.1 even when using icc's linker.
-Chinh Nguyen
email@hidden
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