Refactor diagnostics

[janfb]

What does this implement/fix? Explain your changes

• added a separate function for generating posterior samples for a batch of observations (using batching where possible)
• refactor SBC to outsource posterior sampling to that function
• refactor TARP to be similar to SBC
• adapt tutorial

run_sbc or run_tarp will do everything for the user, including posterior sampling. But now it is possible to first obtain posteroir samples and then pass them to _run_sbc and then to _run_tarp, without having to generate them again.

[codecov]

Codecov Report

Attention: Patch coverage is 88.23529% with 8 lines in your changes missing coverage. Please review.

Project coverage is 75.85%. Comparing base (0bdb9c5) to head (66e3b83).

Files	Patch %	Lines
sbi/diagnostics/tarp.py	75.86%	7 Missing ⚠️
sbi/diagnostics/sbc.py	94.44%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1196      +/-   ##
==========================================
- Coverage   84.35%   75.85%   -8.51%     
==========================================
  Files          96       97       +1     
  Lines        7702     7673      -29     
==========================================
- Hits         6497     5820     -677     
- Misses       1205     1853     +648     

Flag	Coverage Δ
unittests	75.85% <88.23%> (-8.51%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
sbi/diagnostics/__init__.py	100.00% <100.00%> (ø)
sbi/utils/diagnostics_utils.py	100.00% <100.00%> (ø)
sbi/diagnostics/sbc.py	95.77% <94.44%> (+0.42%)	⬆️
sbi/diagnostics/tarp.py	67.85% <75.86%> (-10.17%)	⬇️

... and 23 files with indirect coverage changes

[michaeldeistler]

This has a lot of overlap with the PR with the test for MDN calibration, which one should I review?

[janfb]

This has a lot of overlap with the PR with the test for MDN calibration, which one should I review?

this one please. The MDN only adds the test, but copied all the changes from here.

[michaeldeistler]

Awesome! A few comments below.