Index into diag in Tridigaonal * Diagonal

[jishnub]

The impact on performance is largely negligible in common cases, but it might help in reducing branching.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 93.89%. Comparing base (51923a5) to head (7c24094).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1454   +/-   ##
=======================================
  Coverage   93.89%   93.89%           
=======================================
  Files          34       34           
  Lines       15934    15934           
=======================================
  Hits        14961    14961           
  Misses        973      973           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.