Improved itermonomials

[ctsiagkalis]

Brief description of what is fixed or changed

itermonomials now computes only the necessary monomials and returns a generator object

Release Notes

• polys
  • itermonomials is now a generator.
  • itermonomials now accepts (besides the list of variables) either a list of degrees (one degree for each variable) or an integer (same degree for all the variables) for either the min_degrees and max_degrees parameters. min_degrees can also be omitted, in which case it corresponds to a 0 (single int) or a list of 0's.

[sympy-bot]

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• polys

  • itermonomials is now a generator. (#16561 by @ctsiagkalis)

  • itermonomials now accepts (besides the list of variables) either a list of degrees (one degree for each variable) or an integer (same degree for all the variables) for either the min_degrees and max_degrees parameters. min_degrees can also be omitted, in which case it corresponds to a 0 (single int) or a list of 0's. (#16561 by @ctsiagkalis)

This will be added to https://github.com/sympy/sympy/wiki/Release-Notes-for-1.5.

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#### Brief description of what is fixed or changed

itermonomials now computes only the necessary monomials and returns a generator object


#### Release Notes

<!-- BEGIN RELEASE NOTES -->

* polys
    * itermonomials is now a generator.
    * itermonomials now accepts (besides the list of variables) either a list of degrees (one degree for each variable) or an integer (same degree for all the variables) for either the `min_degrees` and `max_degrees` parameters. `min_degrees` can also be omitted, in which case it corresponds to a 0 (single int) or a list of 0's.

<!-- END RELEASE NOTES -->

Update

The release notes on the wiki have been updated.

[jksuom]

There is trailing whitespace that should be removed:

File contains trailing whitespace: /home/travis/build/sympy/sympy/sympy/polys/monomials.py, line 43.

This is the first error, there may be others. You can find them by running bin/test quality.

[asmeurer]

Please try to write instructive release notes. I updated it, but please check that what I wrote is correct and that I didn't miss anything.

[asmeurer]

Perhaps we should make the function a generator (with yield statements instead of return).

[ctsiagkalis]

Thanks for all your comments and suggestions.
I updated itermonomials to return always a generator object (even in the trivial cases as you suggested), and also updated the release notes.
@asmeurer
I seem to have some issues with the tests. I tried running bin/test quality monomials.py or python bin/test quality monomials py but it always shows no error and passes the tests. Am I doing this wrong?

[jksuom]

Changing the return type to generator has caused some failures. One of the places that have to be fixed is here

sympy/sympy/integrals/heurisch.py

Lines 566 to 569 in 136766a

	if A > 1 and B > 1:
	monoms = itermonomials(V, A + B - 1 + degree_offset)
	else:
	monoms = itermonomials(V, A + B + degree_offset)

On the two lines, monoms should be defined as tuple(itermonomials(...)). That should take care of a number of errors. You can check them locally by running bin/test heurisch.

[codecov]

Codecov Report

Merging #16561 into master will increase coverage by 0.038%.
The diff coverage is 93.846%.

@@             Coverage Diff              @@
##           master    #16561       +/-   ##
============================================
+ Coverage   73.83%   73.868%   +0.038%     
============================================
  Files         619       619               
  Lines      159454    159488       +34     
  Branches    37430     37446       +16     
============================================
+ Hits       117725    117811       +86     
+ Misses      36270     36224       -46     
+ Partials     5459      5453        -6

[jksuom]

Can you add tests for the degree list cases as well?

[jksuom]

The new test examples look good. One change would still be needed: yield {S(1)} should be yield S(1), that is, it should return the number S(1) instead of the set {S(1}. The relevant examples should then work with set(...) instead of next(...).

[ctsiagkalis]

The new test examples look good. One change would still be needed: yield {S(1)} should be yield S(1), that is, it should return the number S(1) instead of the set {S(1}. The relevant examples should then work with set(...) instead of next(...).

You are right. I'll change it for consistency in the tests. I will also change lines 38-40 in test_monomials.py to use set() instead of next().

EDIT:
Messed up the commit message so i force-pushed to change it.

[jksuom]

I think this is ready to be merged. The old total degree part could probably be implemented better as a generator but that is not necessary in this PR. Thank you for your contribution.

[ctsiagkalis]

I think this is ready to be merged. The old total degree part could probably be implemented better as a generator but that is not necessary in this PR. Thank you for your contribution.

I am glad I helped. This was my first PR and I have to admit that you helped me very much. Thank you for everything.