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Beginner
32 Views

Access violation : sounds a bug in the last SDK ?

Hi,
I have the following code that works well :
#pragma unroll
for(uint i = 0; i < MLT_SAMPLING_TASK_PER_SAMPLER; i++, taskId++)
{
clTask task = tasks[taskId];
clMLTSample sample = task.mltSample;
if (sample.requestNewMLTSample && sample.score > bestScore)
{
bestScore = sample.score;
bestScoreTaskId = taskId;
}
}
#pragma unroll for(uint i = 0; i < MLT_SAMPLING_TASK_PER_SAMPLER; i++, taskId++) { clTask task = tasks[taskId]; clMLTSample sample = task.mltSample; if (sample.requestNewMLTSample && sample.score > bestScore) { bestScore = sample.score; bestScoreTaskId = taskId; } }
But when I replace 2 lines with (to minimize the memory access) I got an access violation !
clMLTSample sample = tasks[taskId].mltSample;
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10 Replies
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Beginner
32 Views

Is this OpenCL or Host code? From the looks of it it looks like a host code so it has nothing to do with Intel OpenCL SDK.
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Beginner
32 Views

No, it is OpenCL kernel code !!!!
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Beginner
32 Views

No reaction from the Intel Team ?
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Highlighted
Employee
32 Views

Hello,

I'm not sure it's legal to use #pragma unroll in OpenCL C code. Does the problem persist when you remove those instructions?

Doron Singer
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Beginner
32 Views

It is something that I have found on the Intel pages... so at least for the Intel SDK it should work.
Anyway, I have test without... and I still have the crash :-(
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Employee
32 Views

Good. Next question: What is a "clTask"? Is it a typedef to an OpenCL native type, or is it some user-defined struct?
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Beginner
32 Views

clTask is a typedef to a struct.
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Employee
32 Views

I'm not sure the assignment operator is defined for structs in C. You can use the printf extension to make sure the struct doesn't contain garbage data after the assignment.
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Beginner
32 Views

Assignment operation for structs is very much defined in C (http://en.wikipedia.org/wiki/Struct_%28C_programming_language%29#Assignment).

These 2 pieces of code are identical in their functionality for a good compiler. Lazy compiler might allocate space from stack for clTask task but those days are long gone.
clTask task = tasks[taskId];
clMLTSample sample = task.mltSample;

clMLTSample sample = tasks[taskId].mltSample;

If the only difference between working and non working version are those pieces of code then this indeed is a bug in Intel's implementation.
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Highlighted
Employee
32 Views

In that case, we'll look into this.
Thanks for reporting (in case it's not obvious from my posts, I'm not on the compiler side of things :))

Doron
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