在四个CPU内核/八个CPU线程上执行一个程序

Question

I would like to execute (Java 7) the following algorithm on a quadricore i7 CPU so that the latter would be 100% dedicated to executing it.

long n = 1000000;
int a = 5;
long sum = 0;

for (long i = 1; i <= n; i ++) {
    for (long j = 1; j <= i; j ++) {
        for (long k = 1; k <= j; k *= a) {
            sum ++;
        }
    }
}
System.out.println("Sum = " + sum);

I already took advantage of a manual solution ( java.util.concurrent.Executors , java.util.concurrent.FutureTask ...) where I would create four tasks :

• the first one would execute within the range 1 to n/4;
• the second one would execute within the range (n/4 + 1) to n/2;
• the third one would execute within the range (n/2 + 1) to 3n/4;
• the fourth one would execute within the range (3n/4 + 1) to n.

I was wondering if there's a straightforward/automatic solution to command the OS (I am using Windows) to dedicate "all" of the available CPU resources when this program is executed?

Answer 1

I do not know if this is available under either Java or Windows. In C/C++ under a UNIX-type OS, you can (with the appropriate privileges) re-prioritize your application to a negative priority level. Negative priorities are typically referred to as "real-time priorities", since the OS will not adjust them, and they will get priority over (almost) everything else on the system.

I think the best you can do in Java is use the Runtime.getRuntime().availableProcessors() method to determine how many processors you have, and allocate at least that many threads.

Answer 2

AFAIK There is no straight forward/automatic solution to command in the OS(general OS windows, linux). But In RTOS(Real Time OS) you can divide you'r task and dedicate "all" of the available CPU resources when you'r program is executed.