Katana Login Node Scratch Disk Usage

In this page, the procedure for using the login node's scratch for running jobs interactively or in an interactive batch environment is described. Unlike the compute nodes' scratch, the login node's scratch is always mounted. On the login node, you can access it simply with

katana:~ % cd /scratch/mydir
    or
katana:~ % cd /net/katana/scratch/mydir

In an interactive batch environment, you are actually on a compute node, so that "cd /scratch" will send you to "/net/katana-aXX/scratch".

It is recommended that the user store files in a user-created sub-directory (mkdir /scratch/userID) for the user's own file management purposes.

Enclosed below is an MPI FORTRAN program in which each processor (or rank, in MPI terminology) writes its rank number (as output) to the Katana scratch in a file whose name has the rank built into it. The master process (or rank 0) writes also the sum of the ranks to its corresponding file.

      Program Scratch_Example
      implicit none
      include "mpif.h"
      integer p, total, ierr, master, myid, my_int, dest, tag
      character*40 filename
      data master, tag, dest/0, 0 ,0/
      
c**Starts MPI processes ...
      call MPI_Init(ierr)                            ! starts MPI
      call MPI_Comm_rank(MPI_COMM_WORLD, myid, ierr) ! get current process id
      call MPI_Comm_size(MPI_COMM_WORLD, p, ierr)    ! get # procs

C**define and open output file for each rank to katana LOGIN NODE scratch
      write(filename,"('/scratch/kadin/myoutput.dat.',i1)")myid
      open(unit=11, file=filename,form='formatted',status='unknown')

      my_int = myid    ! result of local proc
C**write local output to its own output file
      write(11,"('Contents of process ',i2,' is ',i8)")myid,my_int

      call MPI_Reduce(my_int, total, 1, MPI_INTEGER, MPI_SUM, dest,
     &                  MPI_COMM_WORLD, ierr)

      if(myid .eq. master) then
        write(11,*)'The sum is =', total    ! writes total to master output file
      endif

      close(11)
      call MPI_Finalize(ierr)                     ! MPI finish up ...
      end

Before running the job, you need to create the subdirectory kadin, expected in the source program above, if it doesn't already exist.

katana:~ % cd /scratch
katana:~ % mkdir kadin

katana:~ % cd /scratch/kadin                                            
katana:/scratch/kadin % pwd
/scratch/kadin
katana:/scratch/kadin % ls
myoutput.dat.0  myoutput.dat.1  myoutput.dat.2  myoutput.dat.3  
katana:/scratch/kadin % cat my*
Contents of process  0 is        0
 The sum is =           6
Contents of process  1 is        1
Contents of process  2 is        2
Contents of process  3 is        3
katana:/scratch/kadin %