Summary: | Small change in FFT size results in 100x slower FFT using default backend | ||
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Product: | Eigen | Reporter: | John Abedor <jabedor> |
Component: | Unsupported modules | Assignee: | Nobody <eigen.nobody> |
Status: | CONFIRMED --- | ||
Severity: | Performance Problem | CC: | chtz, gael.guennebaud |
Priority: | Normal | ||
Version: | 3.3 (current stable) | ||
Hardware: | All | ||
OS: | All | ||
Whiteboard: |
Description
John Abedor
2019-05-17 21:02:42 UTC
I'm pretty sure this is mostly because 100000 nicely factorizes into numbers <=5 but 100001 does not. Very likely FFTW does much more sophisticated things to work on "odd-sized" inputs (i.e., sizes with large factors). If anyone knows how to implement this for the default backend (without entirely copying FFTW), patches are welcome. An obvious workaround is of course to use the FFTW-backend, if necessary. -- GitLab Migration Automatic Message -- This bug has been migrated to gitlab.com's GitLab instance and has been closed from further activity. You can subscribe and participate further through the new bug through this link to our GitLab instance: https://gitlab.com/libeigen/eigen/issues/1717. |