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My MacBookPro, running BootCamp, has an Intel i7-640M processor, which has 2 cores. Like all the other i7 chips, each core is hyperthreaded, so you can have up to 4 threads. Using Visual Studio 2010 c/c++ to determine these:
coresAvailable = omp_get_num_procs ( );
threadsAvailable = omp_get_max_threads ( ) ;
The "threadsAvailable" comes back with a value of 4, as expected. But "coresAvailable" also is reported as 4.
What am I missing?
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The advantage of having several cores is that each core can handle a different data thread simultaneously, allowing for a much quicker transfer of data at any given time. A high clock speed means faster processor.
Up to a certain amount, more cores is more important to most users, even those with a program or two that relies on a single thread for itself. The operating system runs more than one thread, no matter which personal programs you use.
A i7-2670QM processor has 4 cores. But it can run 8 threads in parallel. This means that it only has 4 processing units (Cores) but has support in hardware to run 8 threads in parallel.
Threads are the virtual components or codes, which divides the physical core of a CPU into virtual multiple cores. A single CPU core can have up-to 2 threads per core. For example, if a CPU is dual core (i.e., 2 cores) it will have 4 threads.
omp_get_num_procs returns the number of CPUs the OS reports, and since a hyperthreaded core reports itself as 2 CPUs, a dual-core hyperthreaded chip will report itself as 4 processors.
omp_get_max_threads returns the most threads that will be used in a parallel region of code, so it makes sense that the most threads it will use will be the number of CPUs available.
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