Call BranchMorpher after dw deduplication

[kaushikcfd]

Some timings on the graphs (~36k nodes) implemented in https://github.com/illinois-ceesd/drivers_y2-isolator:

With this patch:

$ time python -O -m mpi4py isolator_injection_run.py -i run_params_combustion.yaml -r restart_data/isolator_init-000000 --log --lazy
real    2m48.997s
user    2m51.500s
sys     0m10.912s

Without this patch:

$ time python -O -m mpi4py isolator_injection_run.py -i run_params_combustion.yaml -r restart_data/isolator_init-000000 --log --lazy                                                                                                                                                                                                                                             
real    3m20.631s                                                                                                                                                                                                                              
user    3m22.686s                                                                                                      
sys     0m11.08

[inducer]

Please add more context to the docstring, contrastng with CachedMapper and specifically mentioning that this is about equality after the mapper applies, and describe the resulting complexity reduction.

[kaushikcfd]

Done!

[inducer]

Thanks! A few more notes/thoughts below.

[inducer]

Suggested change

	A mapper that reuses the same object instances for equal segments of
	graphs.
	A mapper that reuses the same object instances for segments of
	graphs that become equal after processing by subclasses of this mapper,
	where the equality test happens immediately after a new node is created.

[inducer]

Suggested change

	equal array expressions but unequal instances, and because of this it
	different instances representing equal array expressions, and, because of this, it

[inducer]

I think what you want to say instead here is that this avoids building potentially large repeated subexpexpressions in the first place, rather than having to (expensively) merge them after the fact.

[inducer]

Hmm, wait. If it's used like this, I would argue that that's equivalent to just using a CopyMapper. I figured the data-wrapper-deduplicator should inherit from this to avoid building large identical subtrees in the first place.

[inducer]

Added test_post_map_equal_node_reuser_intestine to investigate whether this is equivalent to a CopyMapper, and at least in that example, it appears to be. It remains to figure out where the difference in execution time comes from.

[inducer]

Still: "morph" isn't good terminology.