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Hello,

I can successfully use the PARDISO to solve my problem with iparm(4)=0. However when I try to use it as an iterative solver by setting iparm(4)=61 and keepping all the other parameters the same, it gives error. I turn on msglvl=1 to check the detail, and it says:

---------------------------------------------------------------------------------------------------------------------------------

=== PARDISO is running in In-Core mode, because iparam(60)=0 ===

Percentage of computed non-zeros for LL^T factorization

37 % 87 % 100 %

*** Error in PARDISO ( numerical_factorization) error_num= -1

*** Error in PARDISO: cgs error iparam(20) -22

=== PARDISO: solving a complex nonsymetric system ===

The local (internal) PARDISO version is : 103911000

1-based array indexing is turned ON

PARDISO double precision computation is turned ON

Minimum degree algorithm at reorder step is turned ON

Single-level factorization algorithm is turned ON

Summary: ( starting phase is reordering, ending phase is solution )

================

Times:

======

Time spent in calculations of symmetric matrix portrait (fulladj): 0.000010 s

Time spent in reordering of the initial matrix (reorder) : 0.000014 s

Time spent in symbolic factorization (symbfct) : 0.000065 s

Time spent in copying matrix to internal data structure (A to LU): 0.000000 s

Time spent in factorization step (numfct) : 0.000088 s

Time spent in iterative solver at solve step (cgs) : 0.000259 s cgx iterations -22

Time spent in allocation of internal data structures (malloc) : 0.002747 s

Time spent in additional calculations : 0.000025 s

Total time spent : 0.003208 s

Statistics:

===========

< Parallel Direct Factorization with number of processors: > 6

< Hybrid Solver PARDISO with CGS/CG Iteration >

< Linear system Ax = b >

number of equations: 4

number of non-zeros in A: 8

number of non-zeros in A (%): 50.000000

number of right-hand sides: 4

< Factors L and U >

< Preprocessing with multiple minimum degree, tree height >

< Reduction for efficient parallel factorization >

number of columns for each panel: 128

number of independent subgraphs: 0

number of supernodes: 2

size of largest supernode: 2

number of non-zeros in L: 8

number of non-zeros in U: 1

number of non-zeros in L+U: 9

gflop for the numerical factorization: 0.000000

gflop/s for the numerical factorization: 0.000364

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In this example I use phase=13. I also tried to use phase=11 with iparm(4)=0 and then followed by phase=23 with iparm(4)=61. It gives similar error message.

For the above example, the other non zero iparms I use is:

iparm(1)=1

iparm(3)=1

iparm(10)=13

. I also tried to use the iparm in the example file pardiso_unsym_complex_f.f , but similar error message appears.

How should I modified the code to make the iterative solver works? Thank you.

Best regards,

CC

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Hi,

Based on manual it's mean that iterative algorithm show slow convergence that can happened in case when main matrix and matrix for preconditioner differ a lot. I've modified example pardiso_complex_unsym_f and didn't got such error - which version of MKL do you use?

With best regards,

Alexander Kalinkin

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