Access violation : sounds a bug in the last SDK ?

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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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.

No, it is OpenCL kernel code !!!!

No reaction from the Intel Team ?

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

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 :-(

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

clTask is a typedef to a struct.

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.

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.

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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