Big potential speedup for Jacobian_sparse_CSR::FindFlatIndex()

[Martin Reinecke]

I noticed that Jacobian_sparse_CSR::FindFlatIndex() uses linear search to determine the desired index. However, since the values in mColIdxs are sorted, a bisection search will also work and will be much faster, especially for large matrices.

A quick test showed that switching to bisection search reduced the time for Jacobian generation for the r_process test from about 400 seconds to 40 seconds on my machine.

Would you be interested in a patch?

[Jonas Lippuner]

Definitely!

I knew that the Jacobian generation takes a significant amount of runtime, but I never did more fine-grained profiling to figure out exactly which part dominates. Thank you so much for looking into this, this is awesome!

[Martin Reinecke]

Great!

I can't open a pull request for SkyNet myself, but you can find the patched repository at https://bitbucket.org/mreineck_/skynet/commits/all

[Jonas Lippuner]

If you go to your forked SkyNet repo, then click on Pull requests, then "create pull request" you should be able to create a pull request from your master branch to my master branch.

[Jonas Lippuner]

Pull request merged. Works beautifully, thanks!

[Jonas Lippuner]

Merged