Unsure about some entries in log_summary for 2B DoF problem

Matthew Knepley knepley at gmail.com
Mon May 4 13:09:14 CDT 2009

I believe that the time reported there is collective sum of times divided by
the collective sum
of the stage times. If you look at the time imbalance, it is a staggering
9.7, which either means

  1) The partition is really crap (which we know isn't true)

  2) Some procs spend a lot of time waiting

We can get at this waiting time with the split VecDot() events.


On Mon, May 4, 2009 at 12:58 PM, Richard Tran Mills <rmills at climate.ornl.gov
> wrote:

> PETSc folks,
> I was looking over the log summary data for the 2 billion degrees of
> freedom transport problem, and I'm a bit puzzled by some of the things I'm
> seeing.  (I sent a tarball of this to the pflotran-dev list on April 30.)
>  For instance, looking at the run at 32768 cores, I see that the total time
> for the "transport" phase is 3.2139e+02 seconds.  But if I look at the
> VecDot line for the transport stage, I see
> Event                Count      Time (sec)     Flops   --- Global ---  ---
> Stage ---   Total
>                   Max Ratio  Max     Ratio   Max  Ratio  Mess   Avg len
> Reduct  %T %F %M %L %R  %T %F %M %L %R Mflop/s
> VecDot              1306 1.0 4.1529e+01 9.7 1.76e+08 1.1 0.0e+00 0.0e+00
> 1.3e+03  1  0  0  0  1   3  0  0  0 24 128305
> It's hard to read this the way my email client will wrap it, but it's
> saying that 3% of the time in the stage was spent on VecDot()s.  But the max
> time in VecDot is 4.1529e+01, close to thirteen percent.  Does the "%T" for
> the stage mean something other than what I think it does?
> --Richard
> --
> Richard Tran Mills, Ph.D.            |   E-mail: rmills at climate.ornl.gov
> Computational Scientist              |   Phone:  (865) 241-3198
> Computational Earth Sciences Group   |   Fax:    (865) 574-0405
> Oak Ridge National Laboratory        |   http://climate.ornl.gov/~rmills<http://climate.ornl.gov/%7Ermills>

What most experimenters take for granted before they begin their experiments
is infinitely more interesting than any results to which their experiments
-- Norbert Wiener
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