Fix #178: Make MNT{4,6}-753, cp6_782 tests run conditionally

[z-tech]

Make MNT{4,6}-753, cp6_782 tests run conditionally

Fixes #178
Fixes #180

What does this PR do?

• updates ci.yml so that tests for MNT{4,6}-753 and cp6_782 are run only when either:

  • a) relevant source code changes
  • b) dependencies are updated

• I sanity checked the following conditions:

  • code was updated
  • code was not updated
  • deps were updated
  • deps were not updated

---

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• Targeted PR against correct branch (master)
• Linked to Github issue with discussion and accepted design OR have an explanation in the PR that describes this work.
• Wrote unit tests n/a
• Updated relevant documentation in the code n/a
• Added a relevant changelog entry to the Pending section in CHANGELOG.md n/a
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[Pratyush]

This is a good start! Nice find on the action. However as things stand this is a bit too aggressive, because it doesn't handle when the dependencies change. I think the way to handle that would be to check the current Cargo.lock against the previous Cargo.lock. To perform the comparison we would need to cache the old Cargo.lock.

[z-tech]

Okay sweet I think this does what we want LMK

[Pratyush]

Looks great! Maybe the only diff would be to update the other cache action invocation (line 52) to v3 also.

[Pratyush]

I think we can avoid the mnt4_753-deps-updated- prefix, as the Cargo.lock file is shared across the entire workspace. So we'd be unnecessarily creating an additional cache entry and possibly causing false cache misses if we use this key. Ditto for the other curves.

[z-tech]

That last change didn't result in "cache hits" like I expected...

Does cargo generate-lockfile need to be added before the cache invocation at line 53?

[z-tech]

Second run seems to work as expected. I'll wait for you to let me know when to merge.

[Pratyush]

Mostly looks good to me! A minor optimization that we could do would be to simply check to see if the cache exists, instead of downloading it also. See https://github.com/actions/cache#inputs for how to do this. Thanks for the great work!

[z-tech]

Mostly looks good to me! A minor optimization that we could do would be to simply check to see if the cache exists, instead of downloading it also. See https://github.com/actions/cache#inputs for how to do this. Thanks for the great work!

Sweet! Thanks for the help! I made a little note: arkworks-rs/algebra#720