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Fix issue 16705 - TaskPool.reduce fails to compile "cannot get frame pointer to D main" #4915

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andralex merged 1 commit into from
Nov 20, 2016
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Fix issue 16705 - TaskPool.reduce fails to compile "cannot get frame pointer to D main" #4915

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46 changes: 24 additions & 22 deletions std/parallelism.d
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Original file line number Diff line number Diff line change
Expand Up @@ -33,12 +33,21 @@ Warning: Unless marked as $(D @trusted) or $(D @safe), artifacts in
this module allow implicit data sharing between threads and cannot
guarantee that client code is free from low level data races.

Synopsis:
Source: $(PHOBOSSRC std/_parallelism.d)
Author: David Simcha
Copyright: Copyright (c) 2009-2011, David Simcha.
License: $(HTTP boost.org/LICENSE_1_0.txt, Boost License 1.0)
*/
module std.parallelism;

---
import std.algorithm, std.parallelism, std.range;
///
unittest
{
import std.algorithm : map;
import std.range : iota;
import std.math : approxEqual;
import std.parallelism : taskPool;

void main() {
// Parallel reduce can be combined with
// std.algorithm.map to interesting effect.
// The following example (thanks to Russel Winder)
Expand All @@ -47,32 +56,25 @@ void main() {
// getTerm is evaluated in parallel as needed by
// TaskPool.reduce.
//
// Timings on an Athlon 64 X2 dual core machine:
// Timings on an Intel i5-3450 quad core machine
// for n = 1_000_000_000:
//
// TaskPool.reduce: 12.170 s
// std.algorithm.reduce: 24.065 s
// TaskPool.reduce: 4.011 s
// std.algorithm.reduce: 1.067 s
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@yazd yazd Nov 20, 2016

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The timings are switched, right?

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@PetarKirov PetarKirov Nov 21, 2016

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The timings are for the large case. They are much lower, because I used LDC and a more powerful CPU.

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@yazd yazd Nov 21, 2016 •
edited
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So TaskPool.reduce is slower than the serial algorithm?

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@PetarKirov PetarKirov Nov 21, 2016

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Oh sorry, I didn't notice this before. Yes indeed the two timings should be swapped. I will submit a PR soon.

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@PetarKirov PetarKirov Nov 22, 2016

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Fixed in #4918.


immutable n = 1_000_000_000;
immutable delta = 1.0 / n;
enum n = 1_000_000;
enum delta = 1.0 / n;

real getTerm(int i)
alias getTerm = (int i)
{
immutable x = ( i - 0.5 ) * delta;
return delta / ( 1.0 + x * x ) ;
}
};

immutable pi = 4.0 * taskPool.reduce!"a + b"(
std.algorithm.map!getTerm(iota(n))
);
}
---
immutable pi = 4.0 * taskPool.reduce!"a + b"(n.iota.map!getTerm);

Source: $(PHOBOSSRC std/_parallelism.d)
Author: David Simcha
Copyright: Copyright (c) 2009-2011, David Simcha.
License: $(HTTP boost.org/LICENSE_1_0.txt, Boost License 1.0)
*/
module std.parallelism;
assert(pi.approxEqual(3.1415926));
}

import core.atomic;
import core.exception;
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