Hi Michael - I'll be happy to answer your questions.
1) If you have more places than hosts, then yes, you'll end up with
multiple places on one or more hosts. It assigns place 0 on the first
host, place 1 on the second, etc. When it runs out of hosts, it starts
over again. For example, if you have 2 hosts, but nplaces=5, it will put
places 0,2,4 on host 1, and places 1,3 on host 2.
2) You assign each place to each host using X10_HOSTFILE of X10_HOSTLIST at
startup time. There is no simple way to get the hostname at runtime
currently.
3) X10_NTHREADS defines how many cores should be used by the X10 runtime.
If you have 4 cores, and you want to dedicate all 4 to running a single X10
place, then set X10_NTHREADS to 4. If you have 2 places on the machine,
you would want to divide it in half, setting X10_NTHREADS=2 for each place.
4) X10 assumes you are giving it a valid set of hostnames at initial
startup. If you provide an invalid hostname in X10_HOSTLIST, the launcher
will still attempt to launch a place on that host. Your main program won't
begin running until all places are up and connected, so it shouldn't begin
running at all.
- Ben
From: Michael Dietrich <michael.dietr...@s2010.tu-chemnitz.de>
To: x10-users@lists.sourceforge.net
Date: 08/27/2014 11:34 AM
Subject: [X10-users] Some questions about places
Hello,
I am using X10 as a part of my bachelor's thesis about high
performance programming languages (so maybe some more questions may be
asked later :-) ).
My first questions are about using several places:
* If I set X10_NPLACES=n with having less than n hosts, the places
will be distributed among the existing hosts, right?
* Is there a possibility to find out which place is located on which
host? In Chapel you have here.name.
* Should X10_NTHREADS be equal to the amount of cores within a host?
* Let there be X10_HOSTLIST="A,B,foo". A and B are the hosts I want to
use while foo is a randomly chosen set of letters for simulating a
mistyped or currently inactive computer.
If I start a program with this parameter I don't get an error message
though there is something wrong. If I do isDead() on every place every
of them returns false.
Did I maybe forget to set something so it doesn't distribute the
places to other computers or does X10 ignore host names which cannot
be reached?
Thank you very much
bye
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