[petsc-users] [petsc-maint] Assistance Needed with PETSc KSPSolve Performance Issue

[Yongzhong Li]

Hi Matt,

I have rerun the program with the keys you provided. The system output when performing ksp solve and the final petsc log output were stored in a .txt file attached for your reference.

Thanks!
Yongzhong

From: Matthew Knepley <knepley at gmail.com>
Date: Wednesday, June 12, 2024 at 6:46 PM
To: Yongzhong Li <yongzhong.li at mail.utoronto.ca>
Cc: petsc-users at mcs.anl.gov <petsc-users at mcs.anl.gov>, petsc-maint at mcs.anl.gov <petsc-maint at mcs.anl.gov>, Piero Triverio <piero.triverio at utoronto.ca>
Subject: Re: [petsc-maint] Assistance Needed with PETSc KSPSolve Performance Issue
你通常不会收到来自 knepley at gmail.com 的电子邮件。了解这一点为什么很重要<https://urldefense.us/v3/__https://aka.ms/LearnAboutSenderIdentification__;!!G_uCfscf7eWS!Yfo9Sj1FioTY_hbQkkkF2sbCwllFU-V5CHUuDrxbor7fV_x0ZipVlX0pNA0DVF4dgKpaGDiA3saQdP5M_n-IhQWNlnw5k9ey79U$ >
On Wed, Jun 12, 2024 at 6:36 PM Yongzhong Li <yongzhong.li at mail.utoronto.ca<mailto:yongzhong.li at mail.utoronto.ca>> wrote:
Dear PETSc’s developers, I hope this email finds you well. I am currently working on a project using PETSc and have encountered a performance issue with the KSPSolve function. Specifically, I have noticed that the time taken by KSPSolve is
ZjQcmQRYFpfptBannerStart
This Message Is From an External Sender
This message came from outside your organization.

ZjQcmQRYFpfptBannerEnd
Dear PETSc’s developers,
I hope this email finds you well.
I am currently working on a project using PETSc and have encountered a performance issue with the KSPSolve function. Specifically, I have noticed that the time taken by KSPSolve is almost two times greater than the CPU time for matrix-vector product multiplied by the number of iteration steps. I use C++ chrono to record CPU time.
For context, I am using a shell system matrix A. Despite my efforts to parallelize the matrix-vector product (Ax), the overall solve time remains higher than the matrix vector product per iteration indicates when multiple threads were used. Here are a few details of my setup:

  *   Matrix Type: Shell system matrix
  *   Preconditioner: Shell PC
  *   Parallel Environment: Using Intel MKL as PETSc’s BLAS/LAPACK library, multithreading is enabled
I have considered several potential reasons, such as preconditioner setup, additional solver operations, and the inherent overhead of using a shell system matrix. However, since KSPSolve is a high-level API, I have been unable to pinpoint the exact cause of the increased solve time.
Have you observed the same issue? Could you please provide some experience on how to diagnose and address this performance discrepancy? Any insights or recommendations you could offer would be greatly appreciated.

For any performance question like this, we need to see the output of your code run with

  -ksp_view -ksp_monitor_true_residual -ksp_converged_reason -log_view

  Thanks,

     Matt

Thank you for your time and assistance.
Best regards,
Yongzhong
-----------------------------------------------------------
Yongzhong Li
PhD student | Electromagnetics Group
Department of Electrical & Computer Engineering
University of Toronto
https://urldefense.us/v3/__http://www.modelics.org__;!!G_uCfscf7eWS!Yfo9Sj1FioTY_hbQkkkF2sbCwllFU-V5CHUuDrxbor7fV_x0ZipVlX0pNA0DVF4dgKpaGDiA3saQdP5M_n-IhQWNlnw5Ugt9PLY$ <https://urldefense.us/v3/__http://www.modelics.org__;!!G_uCfscf7eWS!cuLttMJEcegaqu461Bt4QLsO4fASfLM5vjRbtyNhWJQiInbjgNwkGNdkFE1ebSbFjOUatYB0-jd2yQWMWzqkDFFjwMvNl3ZKAr8$>



--
What most experimenters take for granted before they begin their experiments is infinitely more interesting than any results to which their experiments lead.
-- Norbert Wiener

https://urldefense.us/v3/__https://www.cse.buffalo.edu/*knepley/__;fg!!G_uCfscf7eWS!Yfo9Sj1FioTY_hbQkkkF2sbCwllFU-V5CHUuDrxbor7fV_x0ZipVlX0pNA0DVF4dgKpaGDiA3saQdP5M_n-IhQWNlnw5mUCkHxo$ <https://urldefense.us/v3/__http://www.cse.buffalo.edu/*knepley/__;fg!!G_uCfscf7eWS!Yfo9Sj1FioTY_hbQkkkF2sbCwllFU-V5CHUuDrxbor7fV_x0ZipVlX0pNA0DVF4dgKpaGDiA3saQdP5M_n-IhQWNlnw5Y2rcb10$ >
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20240613/cca5c687/attachment-0001.html>
-------------- next part --------------
An embedded and charset-unspecified text was scrubbed...
Name: ksp_petsc_log.txt
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20240613/cca5c687/attachment-0001.txt>