Added support for complex values in QR

[brownbaerchen]

Due Diligence

• General:
  • title of the PR is suitable to appear in the Release Notes
• Implementation:
  • unit tests: all split configurations tested
  • unit tests: multiple dtypes tested
  • NEW unit tests: MPS tested (1 MPI process, 1 GPU)
  • benchmarks: created for new functionality
  • benchmarks: performance improved or maintained
  • documentation updated where needed

Description

As torch supports complex values in QR decomposition, only minimal changes are needed to make heat support it as well. Only the type check needs to be altered and the complex conjugate needs to be taken in a few places, that's it.

There is already a very similar PR open for this (#2040). However, it lacks testing. Here, I added tests. The diff is quite large because I split the test in subtests, but I actually changed very little there.

Issue/s resolved: #2039, #2040

Changes proposed:

• Allow complex values in QR

Type of change

• New feature

[github-actions]

Thank you for the PR!

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.68%. Comparing base (95cb222) to head (75df28a).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2105   +/-   ##
=======================================
  Coverage   91.68%   91.68%           
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  Files          89       89           
  Lines       13945    13945           
=======================================
  Hits        12786    12786           
  Misses       1159     1159           

Flag	Coverage Δ
unit	91.68% <100.00%> (ø)

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