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<b><a class="bz_bug_link
bz_status_NEW "
title="NEW - Fails to compile std.parallelism.reduce"
href="http://bugzilla.gdcproject.org/show_bug.cgi?id=122#c2">Comment # 2</a>
on <a class="bz_bug_link
bz_status_NEW "
title="NEW - Fails to compile std.parallelism.reduce"
href="http://bugzilla.gdcproject.org/show_bug.cgi?id=122">bug 122</a>
from <span class="vcard"><a class="email" href="mailto:russel@winder.org.uk" title="Russel Winder <russel@winder.org.uk>"> <span class="fn">Russel Winder</span></a>
</span></b>
<pre>It is the variant of my π by Quadrature example that David Simcha and I came up
with whilst he was writing parallelism.d:
/*
* A D program to calculate π using quadrature as a parallel reduce of
individual expression evaluations
* with no manual batching.
*
* Copyright © 2011–2013 Russel Winder
*/
// This version originally due to David Simcha, stemming from various emails
on the various D email lists
// and reified in the documentation for std.parallelism:
<a href="http://dlang.org/phobos/std_parallelism.html">http://dlang.org/phobos/std_parallelism.html</a>,
// <a href="http://cis.jhu.edu/~dsimcha/d/phobos/std_parallelism.html">http://cis.jhu.edu/~dsimcha/d/phobos/std_parallelism.html</a>
import std.algorithm;
import std.datetime;
import std.parallelism;
import std.range;
import outputFunctions;
int main(immutable string[] args) {
immutable n = 1000000000;
immutable delta = 1.0 / n;
StopWatch stopWatch;
stopWatch.start();
// There is a problem using a lambda function here. David Simcha reports it
is a consequence of issue
// 5710 <a href="http://d.puremagic.com/issues/show_bug.cgi?id=5710">http://d.puremagic.com/issues/show_bug.cgi?id=5710</a>. Live with this
and use the string syntax
// for specifying a lambda function.
//immutable pi = 4.0 * delta * taskPool.reduce !((a, b) { return a + b; }) (
//immutable pi = 4.0 * delta * taskPool.reduce !((a, b) => a + b) (
immutable pi = 4.0 * delta * taskPool.reduce!"a + b"(
map!((int i) { immutable x = (i - 0.5) * delta; return 1.0 / (1.0 + x *
x); })(iota(n)));
stopWatch.stop();
immutable elapseTime = stopWatch.peek().hnsecs * 100e-9;
output(__FILE__, pi, n, elapseTime);
return 0;
}</pre>
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