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3R1C · Jul 14, 2002, 06:08 AM

I would like to programmatically determine the number of processors a user has on his machine. I know I could do something like:

hostinfo | grep physically | cut -d " " -f1

but this seems 'hackish'

any suggestions?

3R1C · Jul 14, 2002, 06:37 AM

Ok. I've found this:

/usr/include/mach/host_info.h

struct host_basic_info {
integer_t max_cpus; /* max number of cpus possible */
integer_t avail_cpus; /* number of cpus now available */
vm_size_t memory_size; /* size of memory in bytes */
cpu_type_t cpu_type; /* cpu type */
cpu_subtype_t cpu_subtype; /* cpu subtype */
};

looking at this header I can tell that it will give me the info I desire, but I'm clueless as to how to get it programmatically. Im guessing that I would import this header:

#import "/usr/include/mach/host_info.h"

but after that how do I ask how many cpu's there are?
would I:

int foo;
foo = host_info(integer_t,avail_cpus);

Is there any source available which does this?

Gul Banana · Jul 14, 2002, 07:00 AM

I believe what you want is something like this:

<blockquote>code:<hr /><pre style="font-size:x-small; font-family: monospace;">#import "/usr/include/mach/mach_host.h"

int hostInfoCount, numProcessors;
int hostInfoArray[HOST_BASIC_INFO_COUNT];
host_basic_info_t hostInfo;

hostInfoCount = HOST_BASIC_INFO_COUNT;

if(host_info(mach_host_self() , HOST_BASIC_INFO, hostInfo, &hostInfoCount) == KERN_SUCCESS)
{
hostInfo = (host_basic_info_t) hostInfoArray;
numProcessors = hostInfo.avail_cpus;
}</pre><hr /></blockquote>Having now researched the subject in order to find that out, I'd just like to point out that kernel programming is quite evil.

[Edit: I left off a semicolon. ALWAYS the semicolons, isn't it?]

[ 07-14-2002, 08:03 AM: Message edited by: Gul Banana ]

Ibson · Jul 14, 2002, 07:08 AM

I thought I'd point out that #import "/usr/include/mach/mach_host.h" can be re-written as #import <mach/mach_host.h>. I suppose it's just better programming style

.

Gul Banana · Jul 14, 2002, 07:08 AM

I decided to actually test that; after some fiddling, here's something that compiles, runs, and works.

<blockquote>code:<hr /><pre style="font-size:x-small; font-family: monospace;">#include <stdio.h>
#include "/usr/include/mach/mach_init.h"
#include "/usr/include/mach/mach_host.h"

int main (int argc, const char * argv[]) {
int hostInfoCount, numProcessors;
int hostInfoArray[HOST_BASIC_INFO_COUNT];
host_basic_info_t hostInfo;

hostInfoCount = HOST_BASIC_INFO_COUNT;

if(host_info(mach_host_self() , HOST_BASIC_INFO, hostInfoArray, &hostInfoCount) == KERN_SUCCESS)
{
hostInfo = (host_basic_info_t) hostInfoArray;
numProcessors = hostInfo->avail_cpus;
printf("%d", numProcessors);
exit(0);
}

exit(-1);
}</pre><hr /></blockquote>

Gul Banana · Jul 14, 2002, 07:10 AM

<blockquote>quote:<hr />Originally posted by Ibson:
I thought I'd point out that #import "/usr/include/mach/mach_host.h" can be re-written as #import <mach/mach_host.h>. I suppose it's just better programming style

.<hr /></blockquote>You're perfectly right. Here, then:

<blockquote>code:<hr /><pre style="font-size:x-small; font-family: monospace;">#include <stdio.h>
#include <mach/mach_init.h>
#include <mach/mach_host.h>

int main (int argc, const char * argv[]) {
int hostInfoCount, numProcessors;
int hostInfoArray[HOST_BASIC_INFO_COUNT];
host_basic_info_t hostInfo;

hostInfoCount = HOST_BASIC_INFO_COUNT;

if(host_info(mach_host_self() , HOST_BASIC_INFO, hostInfoArray, &hostInfoCount) == KERN_SUCCESS)
{
hostInfo = (host_basic_info_t) hostInfoArray;
numProcessors = hostInfo->avail_cpus;
printf("%d", numProcessors);
exit(0);
}

exit(-1);
}</pre><hr /></blockquote>

3R1C · Jul 14, 2002, 07:18 AM

Evil is right. Im a fledgling cocoa dev at best, and I must admit that the supplied code means little to me. I however thank you. I get two warnings and an error on compile.

warning: implicit declaration of function `mach_host_self'
warning: passing arg 3 of `host_info' from incompatible pointer type
request for member `avail_cpus' in something not a structure or union

Im sure that Im missing something obvious (to everyone but me)

questions:

shouid these be in my .h or my .m?

int hostInfoCount, numProcessors;
int hostInfoArray[HOST_BASIC_INFO_COUNT];

I put everything in my .m

where should I put what? Thanx alot Gul

3R1C · Jul 14, 2002, 07:34 AM

Man you guys are fast! before I could even prepare my question you had answers.

The app Im working on is a prefpane. So the project that was created doesnt have a main.m which is always created when I make an app.

this line from your supplied code:

int main (int argc, const char * argv[])

looks to be that line I always see in the main.m
I have no idea what the main.m is for

Should I make a main.m and put your code in there?

Gul Banana · Jul 14, 2002, 07:41 AM

I'll Objective-Cify that code for you, making it into a method of an object.

In the header of the object file (the .m file such as Thing.m), put
<blockquote>code:<hr /><pre style="font-size:x-small; font-family: monospace;">#include <mach/mach_init.h>
#include <mach/mach_host.h></pre><hr /></blockquote>Now, give the object the following method:

<blockquote>code:<hr /><pre style="font-size:x-small; font-family: monospace;">+ (int)numberOfProcessors
{
int hostInfoCount;
int hostInfoArray[HOST_BASIC_INFO_COUNT];
host_basic_info_t hostInfo;

hostInfoCount = HOST_BASIC_INFO_COUNT;

if(host_info(mach_host_self() , HOST_BASIC_INFO, hostInfoArray, &hostInfoCount) == KERN_SUCCESS)
{
hostInfo = (host_basic_info_t) hostInfoArray;
return (hostInfo-&gt;avail_cpus);
}

return 0;
}</pre><hr /></blockquote>Let's say the class was called NSThing; [NSThing numberOfProcessors] would return the number of available processors or, if an error occurred, 0.

[Edit: adding more information]
As to what <blockquote>code:<hr /><pre style="font-size:x-small; font-family: monospace;">int main (int argc, const char * argv[])</pre><hr /></blockquote>means:
The main function of a program is the one that is called when it runs. In Cocoa applications, this function generally calls NSApplicationMain(), which starts the main run loop. My original code was for a command-line application, in which argc is the number of arguments given and argv is the array of strings containing them (the arguments). To compile that, you would put it in a file such as "cpunum.c" and type "gcc -o cpunum cpunum.c".

If, by the way, you don't understand the stuff before the Edit (how to make a new class and give it a method) I'd recommend you read some more about Cocoa before trying to make a prefpane.

[ 07-14-2002, 08:45 AM: Message edited by: Gul Banana ]

3R1C · Jul 14, 2002, 08:00 AM

Sir: Your skills are potent.

I believe it is working properly, as I have a duallie and it returns 2
I just need a buddy with 1 proc to test my prefpane and I'm golden.

Although I am positive this goes without saying I add the following for others who will read this thread.

This also must go in the .h

+ (int)numberOfProcessors;

thanx again for your tutelage. If a moron like me can get this stuff to work, anyone can dev. =)

Gul Banana · Jul 14, 2002, 08:11 AM

I'm glad I was able to be of help! The code returns 1 for me, by the way, which is indeed the number of processors I have, though obviously the more testing the better.

PipelineStall · Jul 14, 2002, 07:21 PM

You can also use the Multiprocessing Services API (in CoreServices) MPProcessors(). Eg:

<blockquote>code:<hr /><pre style="font-size:x-small; font-family: monospace;">#import <CoreServices/CoreServices.h>

int main(void)
{
printf("Num procs is %d\n", MPProcessors());
return 0;
}</pre><hr /></blockquote>A quick test on my PowerBook shows that this returns 1 CPU. I don't have a dual processor machine to test this with, though.

[ 07-14-2002, 08:25 PM: Message edited by: PipelineStall ]

Kristoff · Jul 14, 2002, 07:46 PM

<blockquote>quote:<hr />Originally posted by PipelineStall:
You can also use the Multiprocessing Services API (in CoreServices) MPProcessors(). Eg:

<blockquote>code:<hr /><pre style="font-size:x-small; font-family: monospace;">#import <CoreServices/CoreServices.h>

int main(void)
{
printf("Num procs is %d\n", MPProcessors());
return 0;
}</pre><hr /></blockquote>A quick test on my PowerBook shows that this returns 1 CPU. I don't have a dual processor machine to test this with, though.<hr /></blockquote>Seems to work....

Num procs is 2

NumCpu has exited with status 0.

On my Dual 800

Gul Banana · Jul 15, 2002, 12:07 AM

Geh, that's much easier! Oh well, I learnt more the other way.

VValdo · Jul 19, 2002, 12:47 AM

Hey all--

I'm just learning cocoa as well (and object oriented programming in general), and here's a pretty easy question I'm sure.. But I'm trying to figure when to make a method an instance method vs. a class method (the Apple docs are pretty oblique).

In this case:

<blockquote>code:<hr /><pre style="font-size:x-small; font-family: monospace;">+ (int)numberOfProcessors
{
int hostInfoCount;
int hostInfoArray[HOST_BASIC_INFO_COUNT];
host_basic_info_t hostInfo;

hostInfoCount = HOST_BASIC_INFO_COUNT;

if(host_info(mach_host_self() , HOST_BASIC_INFO, hostInfoArray, &hostInfoCount) == KERN_SUCCESS)
{
hostInfo = (host_basic_info_t) hostInfoArray;
return (hostInfo-&gt;avail_cpus);
}

return 0;
}</pre><hr /></blockquote>I presume it's made an class method (+) because the result is the same regardless of a particular instance of this class? (Ie, you don't even need one.) Is there a general "rule of thumb" one uses for deciding whether to use a + or -?

Sorry, I'm sure this is pretty elementary. From browsing the various classes, I'm kind of gleaning that a class method doesn't rely on any particular instance of the class existing, which I guess would apply here. Is that basically the deal? Or am I totally confused?

Thanks. I'm gonna use the above code in something I'm working on, if that's cool... <img border="0" title="" alt="[Wink]" src="wink.gif" />
W

Gul Banana · Jul 20, 2002, 05:28 AM

You're basically right about the reason I chose to make it a class method. You could have, then, an abstract class - say, HardwareReporter - with a number of similar methods, and just call them whenever you needed the information, without having to instantiate anything. There's no problem with calling a class method on something that _does_ have instances, so it was a case of this-might-make-things-better-and-won't-make-them-worse. Feel free to use the code; I relinquish any rights to it whatsoever. PipelineStall's way of doing it might be better, actually.. less efficient, but more high level. (Is that a tautology?)

lindberg · Jul 21, 2002, 01:00 PM

Just for completeness, here's how you get the value using sysctl(). This way is a little bit more portable than the others.

<blockquote>code:<hr /><pre style="font-size:x-small; font-family: monospace;">#include <sys/sysctl.h>

int NumProcessorsSysctl()
{
int mib[2];
int numprocs = 0;
size_t len = sizeof(numprocs);

mib[0] = CTL_HW;
mib[1] = HW_NCPU;
sysctl(mib, 2, &numprocs, &len, NULL, 0);
return numprocs;
}</pre><hr /></blockquote>