🚀 go-pugleaf

In article <1jpojvINNin@fnnews.fnal.gov>, kreymer@fnsg01.fnal.gov (Art Kreymer) writes:
|>    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:
.. deleted...

There is another strange behaviour: On the VAX you obtain moreless the same
results (in KB/s) if you declare DATA as integer*1(character),integer*2,
integer*4, integer*8;if you do unformatted write. This is normal because
the write are buffered. This happens also with the VESTed images omn the
Alpha.

With native code on the Alpha you obtain very good result with i*8
(and low cpu/elapsed ratio) and very bad result with i*1 (with cpu/elaps
that is close to 1.).

OK. Now I can declare an equivalence of my character buffer with a REAL*16
buffer, I can do all my operation with the character buffer and then do the
I/O with the REAL*16 buffer. I can achieve very good performance but

WHY ON THE VAX I DON'T NEED TO DO THESE TRICKS?
--
						Ciao, Michele
******************************************************************************
* Michele Michelotto, INFN Padova, Delphi group.                             *
* Internet: michelot@dxcern.cern.ch     BITNET: MICHELOTTO@IPDINFN           *
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