bdsqr: Fix INFO return when NCVT=NRU=NCC=0#1285
Open
jschueller wants to merge 1 commit into
Open
Conversation
Problem: When NCVT = NRU = NCC = 0 (no singular vectors requested), BDSQR calls the dqds algorithm. If dqds failed with INFO = 1 or 3, the routine returned immediately with that error, even though the standard QR algorithm could still compute the singular values. Only INFO = 2 triggered the fallback. Change `IF( INFO .NE. 2 ) RETURN` to `IF( INFO .EQ. 0 ) RETURN` after the dqds call, so the standard QR fallback runs on any dqds failure (INFO=1,2,3) and not only INFO=2. Closes Reference-LAPACK#242
langou
approved these changes
Jun 11, 2026
Contributor
|
Looks good to me. Thanks! |
martin-frbg
approved these changes
Jun 11, 2026
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
3 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Problem: When NCVT = NRU = NCC = 0 (no singular vectors requested), BDSQR calls the dqds algorithm. If dqds failed with INFO = 1 or 3, the routine returned immediately with that error, even though the standard QR algorithm could still compute the singular values. Only INFO = 2 triggered the fallback.
Change
IF( INFO .NE. 2 ) RETURNtoIF( INFO .EQ. 0 ) RETURNafter the dqds call, so the standard QR fallback runs on any dqds failure (INFO=1,2,3) and not only INFO=2.Closes #242