Re: [Polybench-discussion] cholesky produces NaNs

[Louis-Noel P. <po...@cs...>]

Hi Sven,

No it's not expected in the sense the output should not contain NaN, and I can reproduce. This implies the way the array is initialized is incorrect (the current system cannot be solved with Cholesky algo).
I've checked in a fix, now the matrix is SDP and you should not experience NaNs anymore. Initialization takes much longer, I went for the naive solution and get a SDP matrix from a "random" one with matmult...

Thanks,

++

On Aug 10, 2012, at 10:50 AM, Sven Verdoolaege wrote:

> When I compile the cholesky benchmark with -O3.-DPOLYBENCH_DUMP_ARRAYS,
> the output contains lots of NaNs (even for -DMINI_DATASET).
> Is that expected?
> 
> It doesn't look like it's a meaningful result.
> It also makes it difficult to check the correctness of a mapping
> to a CUDA device.  Apparently, the floating point operations on those
> devices are slightly different.  If the results are floating point numbers,
> then you can still compare the results with CPU results by allowing
> some relative error, but some of the NaNs have different signs on
> CUDA vs CPU and so the difference doesn't satisfy any tolerance.
> 
> Could the array be initialized with something that is expected
> to produce meaningful results?
> 
> (This is with revision 31 of https://polybench.svn.sourceforge.net/svnroot/polybench)
> 
> Thanks,
> 
> skimo

-- 
Louis-Noel Pouchet
po...@cs...