Re: multithreaded c++ question

From:

"Ron AF Greve" <ron@localhost>

Newsgroups:

comp.lang.c++

Date:

Tue, 10 Apr 2007 21:01:40 +0200

Message-ID:

<461bdf29$0$325$e4fe514c@news.xs4all.nl>

Hi,

Here is an implementation of my multithreading class (meant to derive from
it and overide run method)

unsigned int __stdcall CPProcess::Spawn(CPProcess *Self)
{
Self->Run();

return 0;
}

bool CPProcess::Start()
{
unsigned int ID = 0;

if( StopEvent = CreateEvent( 0, TRUE, FALSE, 0 ) )
{
  if( !( ThreadID = reinterpret_cast<HANDLE>( _beginthreadex( 0, 0,
reinterpret_cast<unsigned int (__stdcall *)(void *)>( Spawn ), this, 0,
&ID) ) ) )
  {
   CloseHandle( StopEvent );
   StopEvent = 0;
  }
}

return ThreadID != 0;
}

void CPProcess::Stop()
{
SetEvent( StopEvent );

}

bool CPProcess::Wait(ULONG MilliSeconds)
{
if( WaitForSingleObject( ThreadID, MilliSeconds ) == WAIT_OBJECT_0 )
{
  CloseHandle( StopEvent );
  CloseHandle( ThreadID );
  ThreadID = StopEvent = 0;
}

return ThreadID == 0;

}

bool CPProcess::Stopped()
{
return WaitForSingleObject( StopEvent, 0 ) == WAIT_OBJECT_0;
}

void CPProcess::Run()
{
}

Regards, Ron AF Greve

http://www.InformationSuperHighway.eu

"Chris Roth" <czr137@mail.usask.ca> wrote in message
news:evgmnh$fer$1@webmail.usask.ca...

I'm using VS.net 7.1 on Windows XP.

I have a class that hold a container of doubles. One function (foo) for
the class calls a sub-function (bar) for each of the doubles. I'd like to
multithread foo so that the bar sub-functions can run on multiple threads.
I'd like to imlpement this with _beginthreadex as I'm using std::vector.
Please provide some working code around the following details:

#include <windows.h> // for HANDLE
#include <process.h> // for _beginthreadex()
#include <vector>

using namespace std;

class A
{
private:
vector<double> v;
double d; // some other variable common to each thread;
double bar( double x );
public:
vector<double> foo();
};

vector<double> A::foo()
{
vector r( v.size() );
for( int i=0; i<int(v.size()); ++i )
r[i] = bar( v[i] );

return r;
}

double A::bar( double x )
{
double r = x*d; // some function using x and d
// obviosly more complicated in the real code...
return r;
}

Now what I'd like is for multiple instances of bar to run on my two cores.
Can you help me please?