Floating divide by zero error in dfeast_scsrgv

[Dalklint__Anna]

Hi,

I am using the FEAST eigenvalue solver to solve a generalized eigenvalue problem with symmetric sparse matrices in Fortran (Compiler: ifort 2020). I store the upper triangular parts of the matrices, i.e. set UPLO = 'U'.

Currently, I receive an error from ifort "forrtl: error (73): floating divide by zero", which is traced back to the dfeast_scsrgv call. I know that the matrices in the generalized eigenvalue problem may contain small values (i.e. values close to zero). So the sparse patterns might contain zero values. Could this be the cause of the error?

I have tried setting fpm(27) = 1 and fpm(28) = 1 to check input matrices, but this is not recognized by the dfeast_scsrgv call (it isn't listed in the output: List of input parameters fpm(1:64)-- if different from default). Is this a known issue?

Thank you,

Anna

[Ron_Green]

You may want to try the option -no-ftz

https://software.intel.com/content/www/us/en/develop/documentation/fortran-compiler-developer-guide-and-reference/top/compiler-reference/compiler-options/compiler-option-details/floating-point-options/ftz-qftz.html

this may or may not help.  If you think you are in the realm of denormals FTZ could be causing the zeroes.