9b409870a7
git-svn-id: https://svn.code.sf.net/p/lazarus-ccr/svn@5891 8e941d3f-bd1b-0410-a28a-d453659cc2b4
104 lines
3.4 KiB
ObjectPascal
104 lines
3.4 KiB
ObjectPascal
{ Example for a parallel loop with MTProcs.
|
|
|
|
Copyright (C) 2017 Mattias Gaertner mattias@freepascal.org
|
|
|
|
This library is free software; you can redistribute it and/or modify it
|
|
under the terms of the GNU Library General Public License as published by
|
|
the Free Software Foundation; either version 2 of the License, or (at your
|
|
option) any later version with the following modification:
|
|
|
|
As a special exception, the copyright holders of this library give you
|
|
permission to link this library with independent modules to produce an
|
|
executable, regardless of the license terms of these independent modules,and
|
|
to copy and distribute the resulting executable under terms of your choice,
|
|
provided that you also meet, for each linked independent module, the terms
|
|
and conditions of the license of that module. An independent module is a
|
|
module which is not derived from or based on this library. If you modify
|
|
this library, you may extend this exception to your version of the library,
|
|
but you are not obligated to do so. If you do not wish to do so, delete this
|
|
exception statement from your version.
|
|
|
|
This program is distributed in the hope that it will be useful, but WITHOUT
|
|
ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
|
|
FITNESS FOR A PARTICULAR PURPOSE. See the GNU Library General Public License
|
|
for more details.
|
|
|
|
You should have received a copy of the GNU Library General Public License
|
|
along with this library; if not, write to the Free Software Foundation,
|
|
Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
|
|
}
|
|
program parallelloop_nested1;
|
|
|
|
{$mode objfpc}{$H+}
|
|
{$ModeSwitch nestedprocvars}
|
|
|
|
uses
|
|
{$IFDEF UNIX}
|
|
cthreads, cmem,
|
|
{$ENDIF}
|
|
Classes, SysUtils, Math, MTProcs;
|
|
|
|
|
|
function FindBestParallel(aList: TList; aValue: Pointer): integer;
|
|
var
|
|
BlockSize: PtrInt;
|
|
Results: array of integer;
|
|
|
|
procedure InParallel(Index: PtrInt; Data: Pointer; Item: TMultiThreadProcItem);
|
|
var
|
|
i, StartIndex, EndIndex: PtrInt;
|
|
begin
|
|
Results[Index]:=-1;
|
|
StartIndex:=Index*BlockSize;
|
|
EndIndex:=Min(StartIndex+BlockSize,aList.Count);
|
|
//if MainThreadID=GetCurrentThreadId then
|
|
// writeln('FindBestParallel Index=',Index,' StartIndex=',StartIndex,' EndIndex=',EndIndex);
|
|
for i:=StartIndex to EndIndex-1 do begin
|
|
if aList[i]=aValue then // imagine here an expensive compare function
|
|
Results[Index]:=i;
|
|
end;
|
|
end;
|
|
|
|
var
|
|
Index: integer;
|
|
BlockCount: PtrInt;
|
|
begin
|
|
ProcThreadPool.CalcBlockSize(aList.Count,BlockCount,BlockSize);
|
|
SetLength(Results,BlockCount);
|
|
//writeln('FindBestParallel BlockCount=',BlockCount,' List.Count=',aList.Count,' BlockSize=',BlockSize);
|
|
ProcThreadPool.DoParallelNested(@InParallel,0,BlockCount-1);
|
|
// collect results
|
|
Result:=-1;
|
|
for Index:=0 to BlockCount-1 do
|
|
if Results[Index]>=0 then
|
|
Result:=Results[Index];
|
|
end;
|
|
|
|
function FindBestSingleThreaded(List: TList; Value: Pointer): integer;
|
|
var
|
|
i: integer;
|
|
begin
|
|
Result:=-1;
|
|
i:=0;
|
|
while i<List.Count do begin
|
|
if List[i]=Value then // imagine here an expensive compare function
|
|
Result:=i;
|
|
inc(i);
|
|
end;
|
|
end;
|
|
|
|
var
|
|
List: TList;
|
|
i: Integer;
|
|
begin
|
|
List:=TList.Create;
|
|
for i:=0 to 100000000 do
|
|
List.Add(Pointer(i));
|
|
writeln('searching ...');
|
|
i:=FindBestParallel(List,Pointer(List.Count-2));
|
|
writeln('parallel search i=',i);
|
|
i:=FindBestSingleThreaded(List,Pointer(List.Count-2));
|
|
writeln('linear search i=',i);
|
|
end.
|
|
|