OpenMP loops run not parallel

vw61 — Wed, 16 Dec 2009 14:44:25 GMT

Hi,

in our application we have some loops parallelized by OMP. Compiled with VC they run parallel, compiled with Intel compiler they don't.

Some informations to my system: Windows 7 Ultimate, Visual Studio 9.0, Microsoft .Net Framework V. 3.5 SP1. We use an evaluation version of Parallel Studio.

Thanks for any help,
Volker

Re: OpenMP loops run not parallel

Kevin_Magee__Intel_ — Wed, 16 Dec 2009 16:29:49 GMT

Hi,

Please double check that the intel compiler is being invoked with the '/Qopenmp' flag. The setting for this is located in "Configuration Properties>C/C++>Language>OpenMP Support" in the project properties dialog.

If that flag is set, do you have a reproducing case that you can share?

Thanks,

-Kevin

Re: OpenMP loops run not parallel

vw61 — Thu, 17 Dec 2009 14:41:23 GMT

Quoting - Kevin Magee (Intel)

Hi,

the flag is set.

But I have solved the issue.

Here is a little simplified sample of my code:

signed int numTiles = 10;
bool reduceThreads = false, abort = false, badAlloc = false, unknown = false;
omp_set_num_threads(4);

do
{
if (reduceThreads)
{
omp_set_num_threads(1);
reduceThreads = abort = badAlloc = false;
}

#pragma omp parallel for schedule(dynamic, 1)
for (int i = 0; i < numTiles; i++)
{
if (abort)
continue;

unsigned int tileX = i % getNumTilesX();
unsigned int tileY = i / getNumTilesX();
unsigned int state = ACTIVATED;
if (((state & ACTIVATED) == ACTIVATED))
{
try
{
{
#pragma omp critical
removeSomething(tileX, tileY);
}
makeSomething(tileX, tileY);
}
catch (std::bad_alloc&)
{
if (omp_get_num_threads() > 1)
{
reduceThreads = abort = badAlloc = true;
}
else
{
abort = badAlloc = true;
}
//continue;
}
catch (ExGenerationError&)
{
abort = true;
//continue;
}
catch (...)
{
abort = unknown = true;
//continue;
}
}
}
}
while (reduceThreads);

At first the continue statements were not commended. In this case the compiler runs without error message.
But the message OpenMP DEFINED LOOP WAS PARALLELIZED came not.

In the second step I commended the last three continue statements. The message OpenMP DEFINED LOOP WAS PARALLELIZED came and all was nice.

Any explanations?

Thanks,
Volker

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OpenMP loops run not parallel

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