Evaluate Capsul v3 overhead when running many Morphologist pipelines

[sapetnioc]

No description provided.

[denisri]

nb iterations	v2	v3	time factor
50	6.6s	11.8s	x 1.8
500	75s	135s	x 1.8

so capsul v3 is about twice slower than v2 with FOM completion.
It can probably be improved since ProcessMetadata.metadata_modifications() parses parameters on the whole pipeline, is called for each instance of the iteration, and could probably be cached. But not in all cases since the pipeline state may be modified from one iteration to another (if iterating over switches states for instance), so such a cache should depend on the pipeline nodes activation state, at least.

[denisri]

If re-using the same meta_modifications across iterations, the time for 500 iterations completion for Morphologist drops to 32s, which now is 4 times faster, and 2.3 times faster than capsul v2 with FOM.
Now we need to be able to determine (in a fast way) if the pipeline state has changed between iterations. We could store all nodes states with the cache when doing metadata_modifications() perhaps.

[denisri]

The cache has been implemented. The cache hash key takes into account plugs states, and inner nodes states for pipelines. I think it is enough (but if I have forgotten anything, we could fix it).
Completion is now officially faster than v2/FOMs by a factor 2.3. Completion took 32.3s for 500 iterations.

[denisri]

There has been changes in schemas and completion, so we have to re-assess the performance of path completions.

[denisri]

After the merge of the branch rethink_schemas, the time to perform completion for 500 iterations of Morphologist is now 111s. This means that we have gone back to the situation before the cache optimization. I guess the cache has been removed ?