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bryce155

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11-07-2012
06:42 PM

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Parallel iterative solver (CG or FGMRES)

I have a Incomplete Cholesky preconditioner and run the CG using RCI communication and it behaved very poor. THere is only a very little improvement from sequential and parallel mode. It took 80 secs for parallel and 86 for sequential. I am using intel Xeon X5650 2.67. Is it normal for iterative solver? I used the latest MKL 11. It scaled almost linear with direct solver (Pardiso)

Thanks,

Bryce

8 Replies

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Hi,
CG is RCI interface that doesn't affect performance of whole algorithm. Does your implementation of multiplication on stiffness matrix and precondition parallel or not?
With best regards,
Alexander Kalinkin

Alexander_K_Intel2

Employee

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11-07-2012
06:59 PM

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Hi Alex,
Thanks for the prompt response.
I used 2 calls of mkl_dcsrtrsv in the preconditioner solve RCI=3 and mkl_dcsrsymv for matrix multiplication. Does it mean that those function dont perform well in parallel?
Best regards,
Bryce

bryce155

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11-07-2012
07:19 PM

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Bryce, yes, that's may be the problem: level 2 Sparse Triangular solvers (mkl_dcsrtrsv) is not threaded, but computing of m-v product of a sparse symmetrical matrix (mkl_dcsrsymv () ) is threaded.
--Gennady

Gennady_F_Intel

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11-08-2012
01:05 AM

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Ok. Just one more question. Do you plan to include any parallel preconditioner for the iterative solver such as Block Jacobi (or block incomplete cholesky) or multigrid,etc?

bryce155

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11-08-2012
07:40 AM

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Gennady_F_Intel

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11-08-2012
11:18 AM

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the only one thing I can say, that there are no such plans in the nearest release of MKL.

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Thank you Fedorov. I am still wondering the backward and forward substitutions in Pardiso were already parallel. Can we expect the same thing for the triangular solver in the near future?
Thanks,

bryce155

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11-12-2012
11:16 AM

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Gennady_F_Intel

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11-12-2012
09:24 PM

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Hello,
there are no such plans in the nearest future.
Gennady

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yanpu_z_

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04-18-2013
10:37 PM

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I also noticed that when linking the parallel MKL libraries, the backward and forward substitutions (Ax=L*U*x=b<==>L*y=b, U*x=y) is almost the same as its sequential versions. Although the CPU usage is close to 100%, the speed for solving the equation A*x=b is not accelerated at all.

I also expect the triangular solver can be parallized in the near future.

Thanks very much!

For more complete information about compiler optimizations, see our Optimization Notice.