[Wien] Parallelize Spin Up and Down

[Chiung-Yuan Lin]

Dear Prof. Blaha,
 I didn't get a chance to test running spin-up and down for almost one month
because I have
been switching among different machines. Finally, I can settle down in an
IBM p630 with
4 processors. I modify runsp_lapw and run it. It runs without problems. And
the up and dn
tasks don't interfere each other's speed (i.e., 100% parallel efficiency). I
wonder if this means that parallelizing up and dn is useful.
 Chiung-Yuan
 On 8/18/05, Peter Blaha <pblaha at theochem.tuwien.ac.at> wrote:
>
> It is not implemented, since I'm not convinced that it is a usefull
> option.
>
> a) Usually even big magnetic systems require more than 1 k-point (maybe
> not?)
> b) On most dual processor machines I know you will not gain as much as
> expected, because the memory bus is slow and the run-time will increase if
> two lapw1 are running simultaneously.
> Instead, I tend to use a parallel goto-lib which gives a very nice
> speedup (at least for dual Xeons).
>
> Anyway, for a shared memory machine I think it is trivial to
> implement. Test the following:
>
> Change in runsp_lapw the sections lapw1: lapw1c: lapw2: lapw2c:
> and add a "background" & character and a "wait" line
>
> lapw1:
> ....
> if ( "$so" == "-so" ) then
> total_exec lapw1 $it0 -up $para $nohns & <==change
> else
> total_exec lapw1 $it0 -up $para $nohns $orb & <==change
> endif
> if ($icycle >= $in1new ) then
> write_in1_lapw -dn -ql $qlimit >> $dayfile
> if($status == 0 ) cp $file.in1new $file.in1
> endif
> if ( "$so" == "-so" ) then
> total_exec lapw1 $it0 -dn $para $nohns & <==change
> else
> total_exec lapw1 $it0 -dn $para $nohns $orb & <==change
> endif
> wait <==add
> ...
>
> lapw2:
> if ( "$so" == "-so" ) goto lapw2c
> testinput $file.in2 error_input
> total_exec lapw2 -up $para & <==change
> total_exec lapw2 -dn $para & <==change
> wait <==add
>
> And similar in lapw1c and lapw2c sections.
>
> In addition I'd expect that you need to comment the testerror statements
> of the total_exec aliases.
> I think that should do it. Let me know if you are successfull and it is
> usefull.
>
> > I am running a spin-polarized job with only one k-point on a
> > 2-processor machine.
> > If I don't want to do fine grained parallelization, can I distribute
> > spin-up and down tasks into the 2 processors so that they can run
> > simultaneously (for lapw1 and
> > lapw2)?
> >
> > Thanks for your attention,
> > Chiung-Yuan
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