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Hello. I have encountered some unexpected behaviour when using the RCI FGMRES solver.
I am solving a system A x = b with 200 unknowns. A is a badly conditioned matrix (of size 200 x 200), x is the vector we are solving for, and b is the RHS vector (that I know). I also know the correct solution of x.
I am solving this system using both the FGMRES solver with initial solution vector set to zero, and by doing a direct solve using LAPACKE_dgesv.
The solver is used in a c# environment.
I have attached a .zip file containing the code to reproduce the issue. This is a VisualStudio solution which targets .Net framework 4.7.2.
Program.cs contains all the code and input data, and the only dependency are the MKL .dll files. We are using MKL version 2020.0.2.1 and Windows 10 Pro Ver. 21H2.
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Hi David,
Thanks for posting in Intel Communities.
>>We are using MKL version 2020.0.2.1 and Windows 10 Pro Ver. 21H2.
Sorry, we no longer support this product/version. We would like to request you download the latest product as mentioned below and let us know if the issue persists to get further assistance.
https://www.intel.com/content/www/us/en/developer/tools/oneapi/base-toolkit-download.html
Best Regards,
Shanmukh.SS
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Dear Shanmukh,
Thanks for the quick reply.
I confirm the same behaviour in version 2024.0.0
Kind Regards,
David
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The issue can be closed. I realised that ipar[14] was set to the default value 150, i.e. I was running a restarted FGMRES. If I modify this to a higher value the solver does converge in exactly 200 iterations as expected.
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Hi,
It’s great to know that the issue has been resolved, in case you run into any other issues please feel free to create a new thread.
Best Regards,
Shanmukh.SS
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