how to get the number of CPUs?

how to get the number of CPUs?

[Cong]

I'm writing a multithread program to exploit power of CPUs on my Linux
machines. I'm intending to run it on several machines with other
number of CPUs on each of them. So I want to get the number of CPUs
dynamically at run time.

I've googled and learned about sysconf and getconf, but still dont
know will they help me and how to use them. Please help me!

Thank in advance.

Cong

Re: how to get the number of CPUs?

[Bharathi S]

On Thu, 4 Jul 2002, Cong wrote:
> number of CPUs on each of them. So I want to get the number of CPUs
  cpu info is avilable in /proc/cpuinfo file
  if processor is 0 then No. of CPU is 1
  Explore /proc dir you will more idea :)

Bye,
-- 
--==| Bharathi S | BSB-364 DONLab | IIT-Madras |==--
Friendship is enthroned on the strength
That always helps with utmost warmth.
*In Tirukkural of Holy Tamil poet Tiruvalluvar.

RE: how to get the number of CPUs?

[Rupert Wood]

Bharathi S. wrote:

> On Thu, 4 Jul 2002, Cong wrote:
> > number of CPUs on each of them. So I want to get the number of CPUs
>   cpu info is avilable in /proc/cpuinfo file
>   if processor is 0 then No. of CPU is 1
>   Explore /proc dir you will more idea :)

Or the sysconf solution - for Solaris, at least, but this ought to be
portable:

    #include <stdio.h>
    #include <unistd.h>

    int main(void)
    {
        long nProcessorsConfigured = sysconf(_SC_NPROCESSORS_CONF);
        long nProcessorsOnline     = sysconf(_SC_NPROCESSORS_ONLN);

        if (nProcessorsConfigured != -1)
        {
            printf("Processors configured :
%ld\n",nProcessorsConfigured);
        }
        else
        {
            printf("Unable to read configured processor count.\n");
        }

        if (nProcessorsOnline != -1)
        {
            printf("Processors online     : %ld\n",nProcessorsOnline);
        }
        else
        {
            printf("Unable to read online processor count.\n");
        }

        return 0;
    }

Try 'man sysconf' to get a list of supported sysconf arguments and their
descriptions on your platform.

Rup.

Re: how to get the number of CPUs?

[Cong]

Thank you, your code works for me!

But, when I do man sysconf on Linux, it show no infomation
about _SC_NPROCESSORS_CONF as manpage on Solaris do. However, looking
at <unistd.h>, they're there!

Cong

> > On Thu, 4 Jul 2002, Cong wrote:
> > > number of CPUs on each of them. So I want to get the number of CPUs
> >   cpu info is avilable in /proc/cpuinfo file
> >   if processor is 0 then No. of CPU is 1
> >   Explore /proc dir you will more idea :)
> 
> Or the sysconf solution - for Solaris, at least, but this ought to be
> portable:
> 
>     #include <stdio.h>
>     #include <unistd.h>
> 
>     int main(void)
>     {
>         long nProcessorsConfigured = sysconf(_SC_NPROCESSORS_CONF);
>         long nProcessorsOnline     = sysconf(_SC_NPROCESSORS_ONLN);
> 
> Try 'man sysconf' to get a list of supported sysconf arguments and their
> descriptions on your platform.
> 

Re: how to get the number of CPUs?

[Nix]

On Sun, 7 Jul 2002, Cong yowled:
> Thank you, your code works for me!
> 
> But, when I do man sysconf on Linux, it show no infomation
> about _SC_NPROCESSORS_CONF as manpage on Solaris do. However, looking
> at <unistd.h>, they're there!

The manpage is not the canonical information source for the GNU C
library.

Try `info libc processor resources', or
`info libc --index-search=_SC_NPROCESSORS_CONF'.

-- 
`There's something satisfying about killing JWZ over and over again.'
                                        -- 1i, personal communication

RE: how to get the number of CPUs?

[Dockeen]

In case anyone cares, the specified code works on a Win98 PC 
running Cygwin...

Coolies!!!!!!!

Thanks,
Wayne Keen