[Users] Cactus-built LAPACK, BLAS giving incorrect results

Erik Schnetter schnetter at cct.lsu.edu
Fri May 27 18:20:43 CDT 2011

On Fri, May 27, 2011 at 5:13 PM, Kelly, Bernard J.
<bernard.j.kelly at nasa.gov> wrote:
> Hi Erik. Responses below ...
> On 5/27/11 4:19 PM, "Erik Schnetter" <schnetter at cct.lsu.edu> wrote:
>>Here are some possible explanations:
>>(1) That's impossible.
>>(2) You sent this on April 1, and the message got delayed.
> Sadly it's happening, and I sent the first report in on 27 May 2011.
>>(3) Some sort of weird compiler problem. Can you re-build from scratch
>>without optimisation? Can you look at the screen when LAPACK/BLAS are
>>compiled to ensure that these are also built without optimisation?
> I wasn't explicitly trying to -avoid- optimisation for this, since this
> was being compiled at the same time as the overall cactus executable.
> (checking ...) the overall config for my machine is passing "-O2" in
> [F77|F90|C|CXX]_OPTIMISE_FLAGS. I've switched this to "-O0", and am
> recompiling ...
> OK; I have a newly built liblapack.a and libblas.a in the scratch
> directory for this unoptimised run. Same (incorrect) result as before.
>>(4) A linker problem, and the code actually uses a different (not the
>>Cactus built-in version) of LAPACK/BLAS. Can you rebuild with
>>SILENT=no as make option, and look at the final link line to see which
>>LAPACK and BLAS versions are used?
> That's not it. I explicitly linked that simple test program against the
> Cactus-built LAPACK + BLAS:
> ifort lapack_test.F90 -o lapack_test.exe
> -L../configs/handpugh/scratch/external/LAPACK -llapack
> -L../configs/handpugh/scratch/external/BLAS -lblas
> ... and that's where I got the wrong results ...

It may still be that another library called "lapack" is found first.
Can you leave out all -L and -l options, and give the library name

ifort lapack_test.F90 -o lapack_test.exe

I'm also trying your example on my notebook, but am still compiling.


Erik Schnetter <schnetter at cct.lsu.edu>   http://www.cct.lsu.edu/~eschnett/

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