pragma omp parallel for

The "pragma omp parallel for" is a directive in OpenMP, which is a programming model for shared memory parallel programming. This directive is used to parallelize a loop by distributing the iterations of the loop among multiple threads, which can execute the iterations concurrently. The "for" keyword specifies that the loop to be parallelized is a "for" loop.

The syntax of this directive is:

#pragma omp parallel for [clause [clause] ...]
for (init-expression; test-expression; incr-expression)
statement

The clauses that can be used with this directive include "private", "reduction", "schedule", "collapse", "nowait", and others, which allow the programmer to customize the parallelization of the loop.

Here is an example of using the "pragma omp parallel for" directive to parallelize a loop that calculates the sum of an array:

int sum = 0;
#pragma omp parallel for reduction(+:sum)
for (int i = 0; i < N; i++) {
sum += array[i];
}

In this example, the "reduction" clause is used to ensure that the variable "sum" is correctly updated by each thread, and the "+" operator specifies that the values of "sum" from each thread should be added together to obtain the final result.