[TMath] Add Gradient and Laplacian methods for arrays

[pitkajuh]

This Pull request:

Changes or fixes:

Dear All. This pull request adds gradient and Laplacian methods for arrays. These can be used to calculate one-dimensional first and second order derivatives. Should there also be methods for calculating higher order derivatives and dimensions?

I am open to any feedback regarding the code.

Checklist:

• tested changes locally
• updated the docs (if necessary)

This PR fixes #14304

[phsft-bot]

Can one of the admins verify this patch?

[ferdymercury]

See my suggestions for Gradient. Consider applying the same kind of changes to Laplacian. Thanks!

[ferdymercury]

Sorry, I edited now, crash should be gone

[pitkajuh]

Changes ok.

[ferdymercury]

Changes ok.

Thanks! From my side, the only thing left is improving the documentation of Laplacian, try copy-pasting from Gradient and adapting.

[pitkajuh]

Changes ok.

Thanks! From my side, the only thing left is improving the documentation of Laplacian, try copy-pasting from Gradient and adapting.

Thank you for providing suggestions and taking your time to review the code.

[ferdymercury]

You are welcome. Min N must be changed for Laplacian. Thanks!

[pitkajuh]

You are welcome. Min N must be changed for Laplacian. Thanks!

Done.

[github-actions]

Test Results

     9 files       9 suites   1d 16h 55m 38s ⏱️
 2 635 tests  2 635 ✅ 0 💤 0 ❌
22 356 runs  22 356 ✅ 0 💤 0 ❌

Results for commit 61618a1.

♻️ This comment has been updated with latest results.

[ferdymercury]

Related post: https://root-forum.cern.ch/t/numerical-derivative-from-array

[ferdymercury]

Why the change in roofitcore and bindings?

Also go to "Files changed" tab and revise the comments on testTMath.cxx, they are marked as resolved by mistake.

Thanks a lot!

[pitkajuh]

Why the change in roofitcore and bindings?

Also go to "Files changed" tab and revise the comments on testTMath.cxx, they are marked as resolved by mistake.

Thanks a lot!

Thank you for commenting. I am not sure what happened, but I think that the changes occured accidentally when merging from updated master branch. Those changes have been removed and I accepted the changes to the to testTMath.cxx.

I noticed that there is one suggestion on TMath.h (https://github.com/root-project/root/pull/15100/files#r1563955528) and I am not whether it has been implemented to the code. I am having an issue trying to resolve this suggestion. For some reason it does not disappear from the files changed tab, and after trying to accept suggestion multiple times, it get added to the code multiple times. So I ended up with something like this

template <typename T>
T *TMath::Gradient(Long64_t n, T *f, double h)
{
   if (!f) {
      ::Error("TMath::Gradient", "Input parameter f is empty.");
      return nullptr;
   } else if (n < 2) {
      ::Error("TMath::Gradient", "Input parameter n=%lld is smaller than 2.", n);
      return nullptr;
   }
  if (!f) {
      ::Error("TMath::Gradient", "Input parameter f is empty.");
      return nullptr;
   } else if (n < 2) {
      ::Error("TMath::Gradient", "Input parameter n=%lld is smaller than 2.", n);
      return nullptr;
   }
  if (!f) {
      ::Error("TMath::Gradient", "Input parameter f is empty.");
      return nullptr;
   } else if (n < 2) {
      ::Error("TMath::Gradient", "Input parameter n=%lld is smaller than 2.", n);
      return nullptr;
   }
  if (!f) {
      ::Error("TMath::Gradient", "Input parameter f is empty.");
      return nullptr;
   } else if (n < 2) {
      ::Error("TMath::Gradient", "Input parameter n=%lld is smaller than 2.", n);
      return nullptr;
   }
   Long64_t i = 1;

I removed the redundant if statements and the suggestion still shows up in the files changed tab. I am not sure what to do.

[ferdymercury]

That might be just a 'browser cache' issue. Refresh your window, now it looks correct to me.

[lmoneta]

LGTM!
Thank you for this new addition in TMath