PETSc挂起MatView()

Question

我试图在马登塞中创建和打印PETSc矩阵。我的MWE是这样的：

static char help[] = "";

#include <petscmat.h>
#include <petscviewer.h>

int main(int argc,char **args)
{
  Mat            A;
  PetscInt       Istart,Iend,m = 2,n = 2;
  PetscErrorCode ierr;
  PetscMPIInt    rank,size;
  PetscViewer    viewer;

  ierr = PetscInitialize(&argc,&args,(char*)0,help);if (ierr) return ierr;
  ierr = MPI_Comm_rank(PETSC_COMM_WORLD,&rank);CHKERRQ(ierr);
  ierr = MPI_Comm_size(PETSC_COMM_WORLD,&size);CHKERRQ(ierr);
  ierr = PetscOptionsGetInt(NULL,NULL,"-m",&m,NULL);CHKERRQ(ierr);
  ierr = PetscOptionsGetInt(NULL,NULL,"-n",&n,NULL);CHKERRQ(ierr);

  ierr = MatCreateDense(PETSC_COMM_WORLD, PETSC_DECIDE, PETSC_DECIDE, m, n, NULL, &A); CHKERRQ(ierr);
  ierr = MatSetUp(A);CHKERRQ(ierr);

  ierr = MatGetOwnershipRange(A,&Istart,&Iend);CHKERRQ(ierr);

  MatZeroEntries(A);

  printf("rank: %d, istart: %d, iend: %d\n", rank, Istart, Iend);

  ierr = MatAssemblyBegin(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);
  ierr = MatAssemblyEnd(A,MAT_FINAL_ASSEMBLY);CHKERRQ(ierr);

  ierr = MatSetOption(A,MAT_SYMMETRIC,PETSC_TRUE);CHKERRQ(ierr);

  ierr = PetscViewerCreate(PETSC_COMM_WORLD,&viewer);CHKERRQ(ierr);
  ierr = PetscViewerASCIIOpen(PETSC_COMM_WORLD, "out.txt", &viewer);
  ierr = MatView(A, viewer); CHKERRQ(ierr);

  ierr = MatDestroy(&A);CHKERRQ(ierr);
  ierr = PetscViewerDestroy(&viewer);CHKERRQ(ierr);
  ierr = PetscFinalize();
  return ierr;
}

问题是，当在多个进程上运行时，程序突然挂起MatView()函数，而不是写入out.txt文件。我在这里做错什么了？

Answer 1

奇怪的是，这是由Lubuntu 18.10的MPI包中的一些bug引起的。我一更新到Lubuntu 19.04，问题就消失了。

提示:在这种情况下，总是尝试运行make check。测试集将自动生成和运行，您可以观察PETSc行为而不需要大量的手工测试和错误。