Compute-sanitizer detecting No Memcheck error?

Accelerated Computing CUDA CUDA Programming and Performance
1

Hello,

I am using computer-sanitizer --tool memcheck [MyAppName] to detect the error sources. Strangely, there is no Memcheck error after the whole scan whilst I can get illegal memory access by using cudaGetLastError(). Is there something i miss from the command line?

Regards

Abdoulaye

2

Without an example to look at, one can only speculate. For example, your code could contain the use of uninitialized data. In different environments, e.g. running with and without compute-sanitizer, this uninitialized data may take different values, which may cause different addresses to be computed, only some of which cause access to data outside existing memory allocations. You could give --tool initcheck a try, but I am not sure what kind of errors it is able to find.

While tools like compute-sanitizer can be a great help, it is best to think of them as complements to, and not replacements for, other software engineering methods, such as code reviews.

3

@njuffa i think that the memcheck keeps running now on my program. On the first time, it executes my kernel functions without any issue until on a particular one (where an illegal address undoubtly occurs) then it becomes stuck from there for at least one hour. Is it normal?

4

codes can run slower under compute-sanitizer

I agree that without an example its just speculation as to what may be happening.

You might wish to try the latest version of CUDA, to see if the problem persists.

5

I have the CUDA 11.7 version. I used to run cuda-memcheck for the same kernel functions in the past but it did not take much time as now. I understand that the program is slower when it comes to do memcheck. I just notified compute-sanitizer takes much longer.

6

@Robert_Crovella I have a very long cuda program so I am going to give an example below :

MyKernel <<<>>>(); // The kernel which is giving illegal memory access.
cudaDeviceSynchronize();
exit(0); // I used this command in order to kill the program then get the errors results from compute-sanitizer.
7

Sorry, that isn’t useful to me. Perhaps others will be able to help.

I wouldn’t be able to offer any further suggestions without a complete example. Yes, I understand that might require considerable effort on your part.

8

@Robert_Crovella I have new stuff for you. By placing cudaGetLastError() right after the faulty kernel, i got “the launch timed out and was terminated”. Apparently, there was timeout but compute-sanitize did not finish yet scanning my kernel.

9

It’s always a good idea to do rigorous, proper CUDA error checking. Particularly when you are having trouble with a CUDA code. I usually advise that people do that before they ask for help on forums.