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add a few more expression simplifications #2211

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merged 12 commits into from
Oct 10, 2022

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valentinsulzer
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@valentinsulzer valentinsulzer commented Aug 2, 2022

Description

A few more simplifications of the expression tree. Spotted these while debugging but I doubt they will be very common

Type of change

Please add a line in the relevant section of CHANGELOG.md to document the change (include PR #) - note reverse order of PR #s. If necessary, also add to the list of breaking changes.

  • New feature (non-breaking change which adds functionality)
  • Optimization (back-end change that speeds up the code)
  • Bug fix (non-breaking change which fixes an issue)

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  • No style issues: $ flake8
  • All tests pass: $ python run-tests.py --unit
  • The documentation builds: $ cd docs and then $ make clean; make html

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  • Code is commented, particularly in hard-to-understand areas
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codecov bot commented Aug 3, 2022

Codecov Report

Base: 99.64% // Head: 99.64% // Increases project coverage by +0.00% 🎉

Coverage data is based on head (e28b196) compared to base (82a705c).
Patch coverage: 100.00% of modified lines in pull request are covered.

Additional details and impacted files
@@           Coverage Diff            @@
##           develop    #2211   +/-   ##
========================================
  Coverage    99.64%   99.64%           
========================================
  Files          361      361           
  Lines        19918    19932   +14     
========================================
+ Hits         19847    19861   +14     
  Misses          71       71           
Impacted Files Coverage Δ
pybamm/expression_tree/binary_operators.py 100.00% <100.00%> (ø)
pybamm/expression_tree/state_vector.py 100.00% <100.00%> (ø)

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@@ -1257,6 +1253,16 @@ def simplified_division(left, right):
r_left, r_right = right.orphans
return (left * r_right) / r_left

# Cancelling out common terms
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Aren't there more simplifications here? I think this catches things like (a*b)/(a*c) but wouldn't catch (b*a)/(c*a)? Is it much overhead to check for these?

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Yeah, just adding things as I see them come up in expression trees

# Or simplify A @ (B @ b +- C @ c) to (A @ B @ b) +- (A @ C @ c) if (A @ B)
# and (A @ C) are constant
# Don't do this if either b or c is a number as this will lead to matmul errors
if (
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Do we need A to be constant here too? I.e. left.is_constant()?

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yeah, good point

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thanks, looks good!

@valentinsulzer valentinsulzer merged commit dbc7a6c into develop Oct 10, 2022
@valentinsulzer valentinsulzer deleted the more-expression-simplifications branch October 10, 2022 15:26
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2 participants