WIP: 0 GNN layers on last IPU + Fingerprinting

[callumm-graphcore]

Changelogs

• Allow having 0 GNN layers (i.e. only the task heads) on the last IPU in a pipeline split

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Checklist:

• Was this PR discussed in an issue? It is recommended to first discuss a new feature into a GitHub issue before opening a PR.
• Add tests to cover the fixed bug(s) or the new introduced feature(s) (if appropriate).
• Update the API documentation is a new function is added, or an existing one is deleted.
• Write concise and explanatory changelogs above.
• If possible, assign one of the following labels to the PR: feature, fix or test (or ask a maintainer to do it for you).

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discussion related to that PR

[DomInvivo]

Approved changes, can merge when all test pass

[s-maddrellmander]

One tiny question, apologies if I'm missing anything here.
But otherwise the logic looks good to me. Interested to see the results of this.

What exactly is the motivation with having no GNN layers on the final IPU, making more space for heads / fine-tuning ?

[s-maddrellmander]

Maybe I'm missing something obvious, in which case apologies.
Aren't you missing the original forward pass in the case the extra_return_names is missing?

Suggested change

	# Keep original code if no extra_return_names
	# Keep original code if no extra_return_names
	else:
	g = self.gnn.forward(g)

My suspicion is that this will fix the failing tests

[callumm-graphcore]

Sorry Sam, this was more about me sharing some extra code with Kerstin than making a change to the library, I will look at your comments tomorrow

[s-maddrellmander]

No worries! Just saw there was an outstanding PR and glanced thought, ping me when there’s something concrete to review. :)

[codecov]

Codecov Report

Merging #488 (5ee8bc1) into main (a8e715c) will decrease coverage by 0.96%.
Report is 68 commits behind head on main.
The diff coverage is 3.27%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #488      +/-   ##
==========================================
- Coverage   71.42%   70.46%   -0.96%     
==========================================
  Files          93       95       +2     
  Lines        8527     8845     +318     
==========================================
+ Hits         6090     6233     +143     
- Misses       2437     2612     +175     

Flag	Coverage Δ
unittests	70.46% <3.27%> (-0.96%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
ipu	49.14% <ø> (ø)