Question

I wonder if in my program I have only 1 thread, can I write it so that the Quad core or i7 can actually make use of the different cores? Usually when i write programs on a Quad core computer, the CPU usage will only go to about 25%, and the work seems to be divided among the 4 cores, as the Task Manager shows. (the programs i wrote usually is Ruby, Python, or PHP, so they may not be so much optimized).

Update: what if i write it in C or C++ instead, and

for (i = 0; i < 100000000; i++) {
  a = i * 2;
  b = i + 1;
  if (a == ...  || b == ...) { ... }
}

and then use the highest level of optimization with the compiler. can the compiler make the multiplication happen on one core, and the addition happen on a different core, and therefore make 2 cores work at the same time? isn’t that a fairly easy optimization to use 2 cores?

Answer 1

No. You need to use threads to execute multiple paths concurrently on multiple CPU’s (be they real or virtual)… execution of one thread is inherently bound to one CPU as this maintains the “happens before” relationship between statements, which is central to how programs work.