[petsc-users] MUMPS error and superLU error

[Hong]

venkatesh:

> On Tue, May 26, 2015 at 9:02 PM, Hong <hzhang at mcs.anl.gov> wrote:
>
>> 'A serial job in MATLAB for the same matrices takes < 60GB. '
>> Can you run this case in serial? If so, try petsc, superlu or mumps to
>> make sure the matrix is non-singular.
>>
> B matrix is singular but I get my result in Petsc and Mumps for small
> matrices.
>

You are lucky to get something out of a singular matrix using LU
factorization, likely due to arithmetic roundoff. Is the obtained solution
useful?

Suggest reading petsc or slepc manual on how to dump out null space when a
matrix is singular.

Hong

>
>> Both mumps and superlu_dist show crash in MatFactorNumeric(). Mumps gives
>> error
>> [16]PETSC ERROR: Error reported by MUMPS in numerical factorization
>> phase: Cannot allocate required memory 65710 megabytes.
>>
>> Does your code work for smaller problems?
>>
> Yes code works for small problems
>
>> Try using more processors?
>>
>> Why use such huge '-mat_mumps_icntl_14 200000' (percentage of estimated
>> workspace increase)? The default is 20. Try 40?
>>
>> Superlu_dist usually uses less memory than mumps, but it also crashes. I
>> guess something wrong with your matrix. Is it singular?
>>
> The B matrix is singular. So Super Lu cant be used is it ?
>
>
>> Run superlu_dist on a slightly smaller matrix with option
>> '-mat_superlu_dist_statprint' which displays memory usage info., e.g.,
>>
> Ok I will do that and check.
>
>> petsc/src/ksp/ksp/examples/tutorials (maint)
>> $ mpiexec -n 2 ./ex2 -pc_type lu -pc_factor_mat_solver_package
>> superlu_dist -mat_superlu_dist_statprint
>> Nonzeros in L       560
>> Nonzeros in U       560
>> nonzeros in L+U     1064
>> nonzeros in LSUB    248
>> NUMfact space (MB) sum(procs):  L\U 0.01 all 0.05
>> Total highmark (MB):  All 0.05 Avg 0.02 Max 0.02
>> EQUIL time             0.00
>> ROWPERM time           0.00
>> COLPERM time           0.00
>> SYMBFACT time          0.00
>> DISTRIBUTE time        0.00
>> FACTOR time            0.00
>> Factor flops 1.181000e+04 Mflops     4.80
>> SOLVE time             0.00
>> SOLVE time             0.00
>> Solve flops 2.194000e+03 Mflops     4.43
>> SOLVE time             0.00
>> Solve flops 2.194000e+03 Mflops     5.14
>> Norm of error 1.18018e-15 iterations 1
>>
>> Hong
>>
>>
>> On Tue, May 26, 2015 at 9:03 AM, venkatesh g <venkateshgk.j at gmail.com>
>> wrote:
>>
>>> I posted a while ago in MUMPS forums but no one seems to reply.
>>>
>>> I am solving a large generalized Eigenvalue problem.
>>>
>>> I am getting the following error which is attached, after giving the
>>> command:
>>>
>>> /cluster/share/venkatesh/petsc-3.5.3/linux-gnu/bin/mpiexec -np 64 -hosts
>>> compute-0-4,compute-0-6,compute-0-7,compute-0-8 ./ex7 -f1 a72t -f2 b72t
>>> -st_type sinvert -eps_nev 3 -eps_target 0.5 -st_ksp_type preonly
>>> -st_pc_type lu -st_pc_factor_mat_solver_package mumps -mat_mumps_icntl_14
>>> 200000
>>>
>>> IT IS impossible to allocate so much memory per processor.. it is asking
>>> like around 70 GB per processor.
>>>
>>> A serial job in MATLAB for the same matrices takes < 60GB.
>>>
>>> After trying out superLU_dist, I have attached the error there also
>>> (segmentation error).
>>>
>>> Kindly help me.
>>>
>>> Venkatesh
>>>
>>>
>>>
>>
>
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