[mvapich-discuss] MPI IO, MPI_Read does not read in correct buffer from previous MPI_Write

[Ryan Crocker]

Hi all, 

So i've written some binary files, the binary output is compatible with ensight gold formatted vector field files.  I can read them in with paraview and they look fine, but what i'd like to do is recover the raw data.   When i read them in all the header files look fine, but when i try to read back in the data vectors i just get all the same number in the vector.  I'm pretty sure it doesn't matter, but i'm writing this on a few hundred cores, and reading on 1.  I posted this on the mpich forum too, but when i tried with mvapich i have the same issue.

 I've posted the write, then subsequent read below.

write snippet:

  call MPI_FILE_OPEN(comm,file,IOR(MPI_MODE_WRONLY,MPI_MODE_CREATE),mpi_info,iunit,ierr)
  
  ! Write header (only root)
  if (irank.eq.iroot) then
     buffer = trim(adjustl(name))
     size = 80
     call MPI_FILE_WRITE(iunit,buffer,size,MPI_CHARACTER,status,ierr)
     buffer = 'part'
     size = 80
     call MPI_FILE_WRITE(iunit,buffer,size,MPI_CHARACTER,status,ierr)
     ibuffer = 1
     size = 1
     call MPI_FILE_WRITE(iunit,ibuffer,size,MPI_INTEGER,status,ierr)
     buffer = 'hexa8'
     size = 80
     call MPI_FILE_WRITE(iunit,buffer,size,MPI_CHARACTER,status,ierr)
  end if
  
  ! Write the data
  disp = 3*80+4+0*ncells_hexa*4
  call MPI_FILE_SET_VIEW(iunit,disp,MPI_REAL_SP,fileview_hexa,"native",mpi_info,ierr)
  call MPI_FILE_WRITE_ALL(iunit,buffer3_hexa(:,1),ncells_hexa_,MPI_REAL_SP,status,ierr)
  disp = 3*80+4+1*ncells_hexa*4
  call MPI_FILE_SET_VIEW(iunit,disp,MPI_REAL_SP,fileview_hexa,"native",mpi_info,ierr)
  call MPI_FILE_WRITE_ALL(iunit,buffer3_hexa(:,2),ncells_hexa_,MPI_REAL_SP,status,ierr)
  disp = 3*80+4+2*ncells_hexa*4
  call MPI_FILE_SET_VIEW(iunit,disp,MPI_REAL_SP,fileview_hexa,"native",mpi_info,ierr)
  call MPI_FILE_WRITE_ALL(iunit,buffer3_hexa(:,3),ncells_hexa_,MPI_REAL_SP,status,ierr)


read snippet:

 parallel_sum(ncells_hexa_,ncells)

  allocate(buffer3(ncells,3))
 
  openfile=trim(workdir)//'/'//'V/V.000002'
  call MPI_FILE_OPEN(comm,openfile,MPI_MODE_RDONLY,mpi_info,iunit,ierr)
  
  ! Read header 
     bsize = 80
     call MPI_FILE_READ(iunit,cbuffer,bsize,MPI_CHARACTER,status,ierr)
     print*,trim(cbuffer)

     bsize = 80
     call MPI_FILE_READ(iunit,cbuffer,bsize,MPI_CHARACTER,status,ierr)
     print*,trim(cbuffer)

     bsize = 1
     call MPI_FILE_READ(iunit,ibuffer,bsize,MPI_INTEGER,status,ierr)
     print*,ibuffer

     bsize = 80
     call MPI_FILE_READ(iunit,cbuffer,bsize,MPI_CHARACTER,status,ierr)
     print*,trim(cbuffer),ncells


   ! Read the data
  disp = 3*80+4+0*ncells*4
  call MPI_FILE_SET_VIEW(iunit,disp,MPI_REAL_SP,fileview_hexa,"native",mpi_info,ierr)
  call MPI_FILE_READ_ALL(iunit,buffer3(:,1),ncells,MPI_REAL_SP,status,ierr)

  disp = 3*80+4+1*ncells*4
  call MPI_FILE_SET_VIEW(iunit,disp,MPI_REAL_SP,fileview_hexa,"native",mpi_info,ierr)
  call MPI_FILE_READ_ALL(iunit,buffer3(:,2),ncells,MPI_REAL_SP,status,ierr)

  disp = 3*80+4+2*ncells*4
  call MPI_FILE_SET_VIEW(iunit,disp,MPI_REAL_SP,fileview_hexa,"native",mpi_info,ierr) 
  call MPI_FILE_READ_ALL(iunit,buffer3(:,3),ncells,MPI_REAL_SP,status,ierr)
    
  ! Close the file
  call MPI_FILE_CLOSE(iunit,ierr) 

Thanks for the help, 

Ryan Crocker
University of Vermont, School of Engineering
Mechanical Engineering Department


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