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fails of tests for QR and LQ decompositions #973
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Stable reproduced, if there is only one parameter NB in input file. That's why there are no fails for general input file.
It seems, root-cause is also clear. Test have 2 cycles
DO 40 IK = 1, NK DO 30 INB = 1, NNBIf
NNB >= 2, then factorized matrix becomes correct again, since factorization is performed byLQT01(orGELQF) due toIK = 1. But ifNNB = 1, then factorization is done byGELS, which callsGEQRFform = nand test fails for next iterations ofIK.Actually, I still have no idea for proper solution to fix this behavior. Construction of the test is complicated. I believe, that we should somehow avoid call of QR in test for LQ.
- added a commit that references this issue
on Jun 13, 2026 Hi @dklyuchinskiy, let us know if #1298 fixes the issue. It should fix something. The difference between GEQRS (before #900) and GELS (after #900) is that GELS scales the matrix A so the QR factorization in output of GELS is scaled and this is not what CHKLQ expects, so what @jschueller in #1298 did is good and should help. Julien.
Hi @dklyuchinskiy, let us know if #1298 fixes the issue. It should fix something. The difference between GEQRS (before #900) and GELS (after #900) is that GELS scales the matrix A so the QR factorization in output of GELS is scaled and this is not what CHKLQ expects, so what @jschueller in #1298 did is good and should help. Julien.
Hi, Julien!
Unfortunately, at the moment I can not double check status of the issue, but looking into PR with proposed fixes I believe it should help. The problem was that QR factorization was being called in tests of LQ for specific configuration NB, M and N, but now it is fixed. Thanks!
Hello!
I have been running tests for QR and LQ (
xlintstd_dtest) and sometimes I have got failures likeUsually, I need to change input file to reproduce error.
My investigation shows, that root-cause is PR 900 with replacement
GELQSbyGELS(in example of LQ). Behavior of the test is changed a bit (seeTESTING/LIN/dchklq.f):Before:
LQT01is called to factorize matrix byGELQFfor every combination of parametersmandnand this factorized matrix is used at any check of test parameterk.Now:
LQT01is again called to factorize matrix, but later arrayAFis cleared toAto callGELSsince factorization is now performed inside call ofGELS. But, unfortunately, ifm = nin call ofGELSthen factorization is done byGEQRFinsteadGELQF(checkSRC/dgels.f). And this is a main difference. For upper triangular matrix QR factorization doing nothing, which lead to failure oftest(1)andtest(2)on the next iteration of parameterk, since arraysAandAFare equal.@angsch please take a look.
Input is attached input qr and lq.txt