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Re: [Bug-apl] apl computer

From: Juergen Sauermann
Subject: Re: [Bug-apl] apl computer
Date: Fri, 26 Aug 2016 21:34:32 +0200
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maybe, maybe not.

Our earlier measurements on an 80-core machine indicated that
the way how the cores connect to the memories seems to determine the
parallel performance that can be achieved in GNU APL.

One can easily prove that for sufficiently large APL arrays (of arbitrary rank) all scalar APL
functions must scale linearly with N on a N-processor PRAM.

See http://link.springer.com/chapter/10.1007%2F978-3-642-61012-7_11 (in German).

One can also show that on the 80-core machine that we used, the performance stops increasing
at fairly low N (around 10) even for very large arrays.

Which means that either the GNU APL parallel implementation of scalar functions is wrong or
that the 80-core machine we used is performance-wise not even near the PRAM model. My best
guess is the latter.

/// Jürgen

On 08/26/2016 08:41 PM, Xiao-Yong Jin wrote:

On Aug 26, 2016, at 1:12 PM, address@hidden wrote:

finally a computer just perfect for gnuapl

Now is the perfect time to invest your time and effort in improving parallel efficiency in gnu-apl.

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