Sparse triangular and diagonal solve bug

[sylee957]

References to other Issues or PRs

Brief description of what is fixed or changed

from sympy import *

m1 = SparseMatrix.diag([1, 2, 3])
m2 = Matrix([[1, 2], [3, 4], [5, 6]])
m1.diagonal_solve(m2)

Dense diagonal solve doesn't have this bug, but sparse diagonal solve is only solving the first column and giving the colunm vector.
Looks like sparse solver is using more inferiorly overridden version.

I've also found same bug for upper and lower triangular solve

Other comments

Release Notes

• matrices
  • Fixed SparseMatrix.diagonal_solve only solving the first column of the RHS matrix.
  • Fixed SparseMatrix.upper_triangular_solve and SparseMatrix.lower_triangular_solve only solving the first column of the RHS matrix.
  • Fixed SparseMatrix.upper_triangular_solve and SparseMatrix.lower_triangular_solve not working if RHS is an immutable matrix.

[sympy-bot]

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• matrices

  • Fixed SparseMatrix.diagonal_solve only solving the first column of the RHS matrix. (#17254 by @sylee957)

  • Fixed SparseMatrix.upper_triangular_solve and SparseMatrix.lower_triangular_solve only solving the first column of the RHS matrix. (#17254 by @sylee957)

  • Fixed SparseMatrix.upper_triangular_solve and SparseMatrix.lower_triangular_solve not working if RHS is an immutable matrix. (#17254 by @sylee957)

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#### References to other Issues or PRs
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#### Brief description of what is fixed or changed

```python
from sympy import *

m1 = SparseMatrix.diag([1, 2, 3])
m2 = Matrix([[1, 2], [3, 4], [5, 6]])
m1.diagonal_solve(m2)
```
Dense diagonal solve doesn't have this bug, but sparse diagonal solve is only solving the first column and giving the colunm vector.
Looks like sparse solver is using more inferiorly overridden version. 

I've also found same bug for upper and lower triangular solve

#### Other comments


#### Release Notes

<!-- Write the release notes for this release below. See
https://github.com/sympy/sympy/wiki/Writing-Release-Notes for more information
on how to write release notes. The bot will check your release notes
automatically to see if they are formatted correctly. -->

<!-- BEGIN RELEASE NOTES -->
- matrices
  - Fixed `SparseMatrix.diagonal_solve` only solving the first column of the RHS matrix.
  - Fixed `SparseMatrix.upper_triangular_solve` and `SparseMatrix.lower_triangular_solve` only solving the first column of the RHS matrix.
  - Fixed `SparseMatrix.upper_triangular_solve` and `SparseMatrix.lower_triangular_solve`  not working if RHS is an immutable matrix.

<!-- END RELEASE NOTES -->

Update

The release notes on the wiki have been updated.

[chankruze]

Looks Good To Me !

[sylee957]

I see there are some other issues with upper_triangular_solve and lower_triangular_solve

m1 = SparseMatrix.diag([1, 2, 3])
m2 = Matrix([[1, 2], [3, 4], [5, 6]])
m1.upper_triangular_solve(m2)

It gives a completely wrong result like Matrix([[1, 2], [3/2, 4], [5/3, 6]])
It may be quick to fix.

[codecov]

Codecov Report

Merging #17254 into master will increase coverage by 0.02%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##            master    #17254      +/-   ##
============================================
+ Coverage   74.548%   74.568%   +0.02%     
============================================
  Files          623       623              
  Lines       161785    161784       -1     
  Branches     37966     37967       +1     
============================================
+ Hits        120608    120640      +32     
+ Misses       35827     35793      -34     
- Partials      5350      5351       +1