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New larft branches - #1399

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Reference-LAPACK:masterfrom
jprhyne:new-larft-branches-only-larft
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New larft branches#1399
jprhyne wants to merge 5 commits into
Reference-LAPACK:masterfrom
jprhyne:new-larft-branches-only-larft

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@jprhyne

@jprhyne jprhyne commented Sep 9, 2026

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Description
As discussed in PR #1373 this is the proposed changes to just larft. I propose adding computing the conjugate transpose of the T factor associated with the LQ and RQ factorizations. (I also took another look at the documentation and fixed the mistakes I made from #1373. Thanks all!)

The key difference between the larft implementation in this PR and #1373 is that I am no longer using larft_ut as the terminating case and thus need to add the new branches to the level 2 implementation.

The current implementation requires us to apply the conjugate transpose of this T factor, so we are effectively always doing I - VT**H V. This allows for a more obvious connection between (QR,LQ) and (QL,RQ), but prevents us from using the space the R or L matrix as a workspace to hold T. This becomes a problem for an algorithm I want to submit to LAPACK where we compute a panel factorization as follows:

Q = I - VTV**H

where we store V and T where Q will be on output. I have a write-up associated with this algorithm I made for my Master's project that I can add if further justification is needed.
Checklist

  • The documentation has been updated.
  • If the PR solves a specific issue, it is set to be closed on merge. (N/A)

@codecov

codecov Bot commented Sep 9, 2026

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Codecov Report

❌ Patch coverage is 66.97531% with 214 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.33%. Comparing base (9eaccc1) to head (bc00df8).
✅ All tests successful. No failed tests found.

Files with missing lines Patch % Lines
SRC/clarft_lvl2.f 66.66% 29 Missing ⚠️
SRC/zlarft_lvl2.f 66.66% 29 Missing ⚠️
SRC/dlarft_lvl2.f 68.23% 27 Missing ⚠️
SRC/slarft_lvl2.f 68.23% 27 Missing ⚠️
SRC/clarft.f 66.23% 26 Missing ⚠️
SRC/zlarft.f 68.67% 26 Missing ⚠️
SRC/dlarft.f 65.27% 25 Missing ⚠️
SRC/slarft.f 65.27% 25 Missing ⚠️
Additional details and impacted files

Impacted file tree graph

@@            Coverage Diff             @@
##           master    #1399      +/-   ##
==========================================
- Coverage   69.36%   69.33%   -0.03%     
==========================================
  Files        6122     6122              
  Lines      486337   486647     +310     
  Branches    23268    23268              
==========================================
+ Hits       337330   337426      +96     
- Misses     148569   148783     +214     
  Partials      438      438              
Components Coverage Δ
BLAS 97.94% <ø> (ø)
CBLAS 96.98% <ø> (ø)
LAPACK 82.30% <66.97%> (-0.09%) ⬇️
LAPACKE 2.17% <ø> (ø)
TMGLIB 55.69% <ø> (ø)
BLAS testing 88.33% <ø> (ø)
CBLAS testing 89.63% <ø> (ø)
LAPACK testing 82.24% <ø> (ø)
LAPACKE testing ∅ <ø> (∅)
Files with missing lines Coverage Δ
SRC/dlarft.f 72.04% <65.27%> (-27.96%) ⬇️
SRC/slarft.f 72.04% <65.27%> (-27.96%) ⬇️
SRC/clarft.f 71.57% <66.23%> (-28.43%) ⬇️
SRC/zlarft.f 71.57% <68.67%> (-28.43%) ⬇️
SRC/dlarft_lvl2.f 68.96% <68.23%> (-29.15%) ⬇️
SRC/slarft_lvl2.f 68.96% <68.23%> (-29.15%) ⬇️
SRC/clarft_lvl2.f 67.41% <66.66%> (-30.74%) ⬇️
SRC/zlarft_lvl2.f 67.41% <66.66%> (-30.74%) ⬇️

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