34 lines
1.2 KiB
C
34 lines
1.2 KiB
C
#include <stdio.h>
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#include <omp.h>
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int main()
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{
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int data[] = {12757923, 12878611, 12878893, 12757923, 15808973, 15780709, 197622519};
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int largest, largest_factor = 0;
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omp_set_num_threads(4);
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/* "omp parallel for" turns the for loop multithreaded by making each thread
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* iterating only a part of the loop variable, in this case i; variables declared
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* as "shared" will be implicitly locked on access
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*/
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#pragma omp parallel for shared(largest_factor, largest)
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for (int i = 0; i < 7; i++) {
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int p, n = data[i];
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for (p = 3; p * p <= n && n % p; p += 2);
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if (p * p > n) p = n;
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if (p > largest_factor) {
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largest_factor = p;
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largest = n;
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printf("thread %d: found larger: %d of %d\n",
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omp_get_thread_num(), p, n);
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} else {
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printf("thread %d: not larger: %d of %d\n",
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omp_get_thread_num(), p, n);
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}
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}
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printf("Largest factor: %d of %d\n", largest_factor, largest);
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return 0;
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}
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