[PATCH] D25346: [test-suite] [Polybench] run tests twice with -ffp-contract=on/off

[Renato Golin via llvm-commits]

rengolin added a comment.

In https://reviews.llvm.org/D25346#564284, @sebpop wrote:

> As I was mentioning, this is intended only for the Polybench, that are following a pretty regular pattern of testing loop kernels.
>  The patch makes 2mm run correctly for CFLAGS="", "-Ofast", and "-O3 -ffp-contract=on".
>  I have not looked at the other failing benchmarks to say whether this can apply to those.
>  I know that oggenc would be impossible to modify like this.


Right. Abe was trying to change the Make/CMake files, which could be a one-size-fits-all solution. If that works, I think we should go with that.

> There are also these resource problems I was mentioning:
> 
> - compilation time will double: e.g., Polly will optimize both kernels,
> - compute time on the device will more than double: running the kernel twice, plus an extra loop over both outputs to compare with FP_TOLERANCE.

Those two are true for all solutions we can come up with. 2mm takes 100s on ARM and 3mm takes 150s. Doubling ~50 could make it several minutes longer.

You were proposing getting something running first, then change later, but with a tolerance of 0.0001 after all aggregations, I think we could have FP=on and that tolerance in fpcmp and just run the default as a first approach, then later expand the FP=off compare.

Of course, that only works if the tolerance is low enough on all 50.

> - memory requirements on the device will almost double: added one extra output array, input arrays are not modified, so no need to duplicate them,

Abe's solution wouldn't incur in additional memory consumption, but it would take longer to prepare/compile/run two completely different models of the same benchmark.

cheers,
--renato


https://reviews.llvm.org/D25346