🚀 go-pugleaf

    There was earlier discussion of I/O problems on some Alpha systems.
    Fortran unformatted I/O to disk seems to be somewhat slower than
    expected, and, surprisingly, is CPU limited. That is, the CPU is
    running at 100% utilization in USER mode while the I/O is in progress.

    The I/O problem is almost certainly related to the Fortran Compiler.
    Note the following timings, writing a 32,000 block (16 Mbyte) file
    composed of records of length 8000 words (32 Kbytes)

    Formatted writes and VESTed images use much less CPU than native
    unformatted writes. Implied I/O do loops suffer no or negative
    overhead.

    Elapsed    CPU    Method
      15         1.   UNFORMATTED  WRITE (1) DATA  (vested image from VAX)
      25.        1.   FORMATTED    WRITE (1,'(A32000)') CDATA
      20.       15.   UNFORMATTED  WRITE (1) DATA  (native image)
      15.       15.   UNFORMATTED  WRITE (1) (DATA(J),J=1,8000)

    Here's the test program:

          PROGRAM WRITE

          PARAMETER ( LEN = 8000 )
          INTEGER DATA ( LEN )
          CHARACTER*(4*LEN) CDATA
          EQUIVALENCE ( CDATA , DATA )

          DO I = 1 , LEN
             DATA(I) = I
          ENDDO

          OPEN ( 1 , FILE = 'TEST' ,
         +   STATUS = 'NEW' ,
         +   FORM = 'UNFORMATTED' ,    ! unformatted
    !     +   FORM = 'FORMATTED' ,     !   formatted
         +   RECL = 8000 ,             ! unformatted
    !     +   RECL = 32000 ,           ! formatted
         +   RECORDTYPE = 'VARIABLE' ,
         +   INITIALSIZE = 32 000 )

          DO I = 1 , 512
             WRITE (1)  DATA                 ! unformatted
    !        WRITE (1) (DATA(J),J=1,LEN)     ! unformatted implied do
    !         WRITE (1, '(A32000)' ) CDATA   !   formatted
          ENDDO

          WRITE (*,*) ' DONE '
          CLOSE (1)

          CALL EXIT
          STOP
          END