May not be beneficial

Accelerated Computing HPC Compilers Legacy PGI Compilers
#1

When a loop in a function that you are trying to compile renders the output:

Loop not parallelized: may not be beneficial

What is it basing its criteria for that response on? It seems a little arbitrary to me.

Also, is there a pgcc command to tell the pgcc compiler to not parallelize a loop if the intensity is below a certain value: say 5.00?

Any help appreciated. Thanks in advance.

Newport_j

#2

What is it basing its criteria for that response on?

It’s generally based on the number of instructions plus other heuristics. There’s overhead required to set-up and tear-down threads so if there isn’t enough work in a loop, parallelization can hurt performance due to this overhead.

  • Mat