You are seeing half precision (like 7 digits) in 10-20% of the entries and full in the rest.
Someone will probably chime in who knows about this but I can see where a serial matrix is printed in ASCII Matlab in MatView_SeqAIJ_ASCII in src/mat/impls/aij/seq/aij.c. I think this line is operative and is should clearly work: ierr = PetscViewerASCIIPrintf(viewer,"%D %D %18.16e\n",i+1,a->j[j]+1,(double)a->a[j]);CHKERRQ(ierr); Could you run in serial (this code could very well be used for MPI Mats also) with Matlab/ASCII to verify that you have this problem. And you could modify this print statement and remake PETSc, if that's easy, to verify that this code is operative. I think %18.16e should print 16 digits even if they are 0s ... On Tue, May 14, 2019 at 8:34 PM Sanjay Govindjee <s...@berkeley.edu> wrote: > I'm seeing half precision on at least 10 to 20% of the entries :( > Knowing I should see full precision, I will dig deeper. > > -sanjay > > On 5/14/19 5:22 PM, Mark Adams wrote: > > I would hope you get full precision. How many digits are you seeing? > > On Tue, May 14, 2019 at 7:15 PM Sanjay Govindjee via petsc-users < > petsc-users@mcs.anl.gov> wrote: > >> I am using the following bit of code to debug a matrix. What is the >> expected precision of the numbers that I will find in my ASCII file? >> As far as I can tell it is not the full double precision that I was >> expecting. >> >> call PetscViewerASCIIOpen(PETSC_COMM_WORLD, >> tangview,K_view, ierr) >> call PetscViewerSetFormat(K_view, >> PETSC_VIEWER_ASCII_MATLAB, ierr) >> call MatView (Kmat, K_view, ierr) >> >> -sanjay >> >> >