Hi Hong,

Thank you for having a look, I copied/pasted your code snippet into ex28.c and the error indeed appears if you change that col[0]. That's because you did not allow a new non-zero location in the matrix with the option MAT_NEW_NONZERO_LOCATION_ERR.

I spent the day debugging the code and already checked my calls to MatSetValues:

For all MatSetValues calls corresponding to the row/col location in the error messages in the subsequent assembly, the numerical value associated with that row/col was exactly (0.0,0.0) (complex arithmetic) so it shouldn't be inserted w.r.t. the option MAT_IGNORE_ZERO_ENTRIES. It seems MatSetValues still did it anyway.

I was able to solve the problem by adding MatSetOption(L,MAT_NEW_NONZERO_LOCATIONS,PETSC_FALSE) after my first assembly. However I don't know why it fixed it as the manual seems to say this is just for efficiency purposes

It "should be specified after the first matrix has been fully assembled. This option ensures that certain data structures and communication information will be reused (instead of regenerated during successive steps, thereby increasing efficiency"

So I'm still puzzled by why I got that error in the first place. Unless "regenerated" implies resetting some attributes of the preallocated non-zero structure / first assembly?


Thibaut


On 22/10/2019 17:06, Zhang, Hong wrote:
Thibaut:
Check your code on MatSetValues(), likely you set a value "to a new nonzero at global row/column (200, 160) into matrix" L.
I tested petsc/src/mat/examples/tests/ex28.c by adding
@@ -95,6 +95,26 @@ int main(int argc,char **args)
   /* Compute numeric factors using same F, then solve */
   for (k = 0; k < num_numfac; k++) {
     /* Get numeric factor of A[k] */
+    if (k==0) {
+      ierr = MatZeroEntries(A[0]);CHKERRQ(ierr);
+      for (i=rstart; i<rend; i++) {
+        col[0] = i-1; col[1] = i; col[2] = i+1;
+        if (i == 0) {
+          ierr = MatSetValues(A[k],1,&i,2,col+1,value+1,INSERT_VALUES);CHKERRQ(ierr);
+        } else if (i == N-1) {
+          ierr = MatSetValues(A[k],1,&i,2,col,value,INSERT_VALUES);CHKERRQ(ierr);
+        } else {
+          ierr = MatSetValues(A[k],1,&i,3,col,value,INSERT_VALUES);CHKERRQ(ierr);
+        }
+      }
+      if (!rank) {
+      i = N - 1; col[0] = N - 1;
+        ierr = MatSetValues(A[k],1,&i,1,col,value,INSERT_VALUES);CHKERRQ(ierr);
+      }
+      ierr = MatAssemblyBegin(A[k],MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
+      ierr = MatAssemblyEnd(A[k],MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
+    }
+

It works in both sequential and parallel. If I set col[0] = 0, then I get the same error as yours.
Hong

    Dear PETSc developers,

    I'm extending a validated matrix preallocation/assembly part of my
    code to solve multiple linear systems with MUMPS at each iteration
    of a main loop, following the example
    src/mat/examples/tests/ex28.c that Hong Zhang added a few weeks
    ago. The difference is that I'm using just 1 matrix to solve
    different systems.

    I'm trying to investigate a nasty bug arising when I try to
    assemble "for a second time" that MPIAIJ matrix. The issue arises
    only in parallel, serial works fine.

    Creating 1 MPIAIJ matrix, preallocating it "perfectly" with the
    case where I have the fewest zero entries in the non-zero
    structure, before getting its symbolic factorization.

    Further in the main loop, I'm solely changing its entries
    *retaining the non-zero structure*.

    Here is the simplified Fortran code I'm using:

    ! Fill (M,N) case to ensure all non-zero entries are preallocated
    CALL set_equations(M,N)

    CALL alloc_matrix(L)
      ! --> Call MatSeqAIJSetPreallocation/MatMPIAIJSetPreallocation
      ! --> Sets MAT_IGNORE_ZERO_ENTRIES,
    MAT_NEW_NONZERO_ALLOCATION_ERR, MAT_NO_OFF_PROC_ENTRIES to true

    CALL assemble_matrix(L)
      ! --> Calls MatSetValues with ADD_VALUES
      ! --> Call MatAssemblyBegin/MatAssemblyEnd

    ! Tell PETSc that new non-zero insertions in matrix are forbidden
    CALL MatSetOption(L,MAT_NEW_NONZERO_LOCATION_ERR,PETSC_TRUE,ierr)

    CALL set_mumps_parameters()

    ! Get symbolic LU factorization using MUMPS
    CALL MatGetFactor(L,MATSOLVERMUMPS,MAT_FACTOR_LU,F,ierr)
    CALL MatGetOrdering(L,MATORDERINGNATURAL,rperm,cperm,ierr)
    CALL MatLUFactorSymbolic(F,L,rperm,cperm,info,ierr)

    CALL initialize_right_hand_sides()

    ! Zero matrix entries
    CALL MatZeroEntries(L,ierr)

    ! Main loop
    DO itr=1, maxitr

      DO m = 1, M
        DO n = 1, N

        CALL set_equations(m,n)
        CALL assemble_matrix(L) ! ERROR HERE when m=1, n=1, CRASH IN
    MatSetValues call

        ! Solving the linear system associated with (m,n)
        CALL MatLUFactorNumeric(F,L,info,ierr)
        CALL MatSolve(F,v_rhs(m,n),v_sol(m,n),ierr)

        ! Process v_rhs's from v_sol's for next iteration

        CALL MatZeroEntries(L,ierr)

        END DO
      END DO

    END DO


    Testing on a small case, the error I get is

    [1]PETSC ERROR: --------------------- Error Message
    --------------------------------------------------------------
    [1]PETSC ERROR: Argument out of range
    [1]PETSC ERROR: Inserting a new nonzero at global row/column (200,
    160) into matrix
    [1]PETSC ERROR: See
    https://www.mcs.anl.gov/petsc/documentation/faq.html
    <https://www.mcs.anl.gov/petsc/documentation/faq.html> for trouble
    shooting.
    [1]PETSC ERROR: Petsc Release Version 3.12.0, unknown
    [1]PETSC ERROR: Configure options --PETSC_ARCH=cplx_gcc_debug
    --with-scalar-type=complex --with-precision=double
    --with-debugging=1 --with-valgrind=1 --with-debugger=gdb
    --with-fortran-kernels=1 --download-mpich --download-fblaslapack
    --download-scalapack --download-metis --download-parmetis
    --download-ptscotch --download-mumps --download-slepc
    --COPTFLAGS="-O0 -g" --CXXOPTFLAGS="-O0 -g" --FOPTFLAGS="-O0 -g
    -fbacktrace"
    [1]PETSC ERROR: #1 MatSetValues_MPIAIJ() line 634 in
    /home/thibaut/Packages/petsc/src/mat/impls/aij/mpi/mpiaij.c
    [1]PETSC ERROR: #2 MatSetValues() line 1375 in
    /home/thibaut/Packages/petsc/src/mat/interface/matrix.c
    [1]PETSC ERROR: #3 User provided function() line 0 in User file
    application called MPI_Abort(MPI_COMM_SELF, 63) - process 0


    which I don't understand. That element was not in the non-zero
    structure and wasn't preallocated. I printed the value to be
    inserted at this location (200,160) and it is exactly
    (0.0000000000000000,0.0000000000000000) so this entry should not
    be inserted due to MAT_IGNORE_ZERO_ENTRIES, however it seems it
    is. I'm using ADD_VALUES in MatSetValues but it is the only call
    where (200,160) is inserted.


        - I zero the matrix entries with MatZeroEntries which retains
    the non-zero structure (checked when I print the matrix) but tried
    to comment the corresponding calls.

        - I tried to set MAT_NEW_NONZERO_LOCATION_ERR AND
    MAT_NEW_NONZERO_ALLOCATION_ERR to PETSC_FALSE without effect.


    Perhaps there's something fundamentally wrong in my approach, in
    any case would you have any suggestions to identify the exact
    problem?

    Using PETSc 3.12.0. Thanks for your support,


    Thibaut

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