Hi all, I do not know if this forum is the most appropriate, but as it based using gfortran I will try to start here.
I usually build the ATLAS library in some beta version without any numerical problem that I remember. In a circumstantial way, I have to use the system ATLAS library and, today, I am getting some incorrect numerical results with the DGBSV lapack fortran subroutine, which is described below with a simple test. Perhaps, I am not using the correct sintaxis in the interface, maybe in the compiler flags or the link ones? Please, any ideas? Thanks in advance. Regards. Jorge. -- A simple test: it is built for the General Band Matrix Factorization and Multiple Right-Hand Side Solver DGBSV lapack fortran subroutine, and it is based from: IBM Documentation SGBSV, DGBSV, CGBSV, and ZGBSV (General Band Matrix Factorization and Multiple Right-Hand Side Solve) https://www.ibm.com/docs/en/essl/6.2?topic=blaes-sgbsv-dgbsv-cgbsv-zgbsv-general-band-matrix-factorization-multiple-right-hand-side-solve $ cat /proc/version Linux version 5.13.19-200.fc34.x86_64 (mockbu...@bkernel01.iad2.fedoraproject.org) (gcc (GCC) 11.2.1 20210728 (Red Hat 11.2.1-1), GNU ld version 2.35.2-5.fc34) #1 SMP Sat Sep 18 16:32:24 UTC 2021 $ sudo dnf --best reinstall atlas* $ which gfortran /usr/beta/gcc-trunk/bin/gfortran $ gfortran --version GNU Fortran (GCC) 12.0.0 20210914 (experimental) $ gfortran -march=native -mtune=native -fall-intrinsics -fcheck=all -fimplicit-none -fmax-errors=4 -fPIC -std=f2018 -Wall -Waliasing -Warray-temporaries -Wcharacter-truncation -Werror -Wextra -Wimplicit-interface -Wimplicit-procedure -Wintrinsic-shadow -Wline-truncation -Wuse-without-only -Wrealloc-lhs-all -Wsurprising -Wtabs -Wuninitialized -Wunused-parameter -Og -o trouble.exe trouble.f90 -L/usr/lib64/atlas -llapack -lf77blas -lcblas -ltatlas (Note: the same results either -ltatlas, -lsatlas, -flto=auto flags). $ ./trouble.exe (snip) info = 1 # <-- i.e. the solution has not been computed. $ cat trouble.f90 module m_interfase implicit none private public :: idp, iin, dgbsv integer, parameter :: idp = kind (1.0d0) integer, parameter :: iin = kind (1) interface subroutine dgbsv (n, kl, ku, nrhs, ab, ldab, ipiv, b, ldb, info) integer info, kl, ku, ldab, ldb, n, nrhs integer ipiv (*) double precision ab (ldab,*), b (ldb,*) external dgbtrf, dgbtrs, xerbla intrinsic max end subroutine dgbsv end interface end module m_interfase ! program trouble use m_interfase, only: iin, idp, dgbsv implicit none real (idp), parameter :: cero = 0.0_idp real (idp), parameter :: uno = 1.0_idp real (idp), parameter :: dos = 2.0_idp real (idp), parameter :: tres = 3.0_idp real (idp), parameter :: cuat = 4.0_idp real (idp), parameter :: cinc = 5.0_idp real (idp), parameter :: seis = 6.0_idp real (idp), parameter :: siet = 7.0_idp real (idp), parameter :: ocho = 8.0_idp real (idp), parameter :: nuev = 9.0_idp real (idp), dimension (9,9), parameter :: & ccc = reshape ( [ & uno, dos, tres, cero, cero, cero, cero, cero, cero, & ! 1 dos, uno, dos, tres, cero, cero, cero, cero, cero, & ! 2 tres, dos, uno, dos, tres, cero, cero, cero, cero, & ! 3 cuat, tres, dos, uno, dos, tres, cero, cero, cero, & ! 4 cero, cuat, tres, dos, uno, dos, tres, cero, cero, & ! 5 cero, cero, cuat, tres, dos, uno, dos, tres, cero, & ! 6 cero, cero, cero, cuat, tres, dos, uno, dos, tres, & ! 7 cero, cero, cero, cero, cuat, tres, dos, uno, dos, & ! 8 cero, cero, cero, cero, cero, cuat, tres, dos, uno & ! 9 ], [9,9]) real (idp), dimension (9,3), parameter :: & vvv = reshape ( [ & uno, uno, uno, uno, uno, uno, uno, uno, uno, & ! 1 uno, -uno, uno, -uno, uno, -uno, uno, -uno, uno, & ! 2 uno, dos, tres, cuat, cinc, seis, siet, ocho, nuev & ! 3 ], [9,3]) real (idp), dimension (9,9) :: aaa real (idp), dimension (9,3) :: bbb integer (iin), dimension (9) :: ipiv integer (iin) :: nn, klo, kup, nrhs, lda, ldb, info integer (iin) :: i ! nn = size (aaa,1) klo = 2 kup = 3 nrhs = size (bbb,2) lda = 2 * klo + kup + 1 ldb = nn aaa = ccc bbb = vvv ipiv = 0 ! write (*,*) write (*,*)" dgbsv (General Band Side) test " write (*,*) write (*,*)" system matrix: aaa " do i = 1, nn write (*,*) real (aaa (i,:)) end do write (*,*) write (*,*)" source: bbb " do i = 1, nn write (*,*) real (bbb (i,:)) end do write (*,*)" nn = ", nn write (*,*)" klo = ", klo write (*,*)" kup = ", kup write (*,*)" nrhs = ", nrhs write (*,*)" lda = ", lda write (*,*)" ldb = ", ldb ! N KL KU NRHS A LDA IPIV B LDB INFO) ! | | | | | | | | | | !call dgbsv (9 , 2 , 3 , 3 , aaa, 8 , ipiv, bbb, 9, info) call dgbsv (nn, klo, kup, nrhs, aaa, lda, ipiv, bbb, ldb, info) ! write (*,*) write (*,*)" output aaa: " do i = 1, nn write (*,*) real (aaa (i,:)) end do write (*,*) write (*,*)" output bbb: " do i = 1, nn write (*,*) real (bbb (i,:)) end do write (*,*) write (*,*)" output ipiv: ", ipiv write (*,*) write (*,*)" info = ", info end program trouble --
