AnsweredAssumed Answered

Incorrect results when multiple processes use the same GPU

Question asked by ajk on Jul 29, 2014
Latest reply on Aug 13, 2014 by benc

Hello. I've noticed strange behaviour of our scientific application when launching several instances on the same GPU - sometimes it gives incorrect results.

I've reproduced this behaviour on the small program (see attachment).

1. It creates two slightly different matrix multiplication kernels.

2. Creates three buffers a, b, c.

3. First kernel multiplies a * b and writes result to c. Second kernel multiplies b * a and writes result to the same c.

4. It launches kernel 1, kernel 2 in the loop several times (at the end of the loop, kernel 1 always), then gets the result back and compares it with gold a * b.

When executing (see attachment): correct result on all platforms (AMD, Intel, NVIDIA).

When executing (which launches 9 instances of the program in parallel): some of the instances gave wrong result on AMD platform (tested on FirePro W9100 with fglrx-13.352.1014 and fglrx-14.20), on Intel and NVIDIA - always correct results.