September 2017 Update

Task/Parallel-calculations/Fortran/parallel-calculations.f

@@ -0,0 +1,54 @@
+program Primes
+
+    use ISO_FORTRAN_ENV
+
+    implicit none
+
+    integer(int64), dimension(7) :: data = (/2099726827, 15780709, 1122725370, 15808973, 576460741, 12878611, 12757923/)
+    integer(int64), dimension(100) :: outprimes
+    integer(int64) :: largest_factor = 0, largest = 0, minim = 0, val = 0
+    integer(int16) :: count = 0, OMP_GET_THREAD_NUM
+
+    call omp_set_num_threads(4);
+    !$omp parallel do private(val,outprimes,count) shared(data,largest_factor,largest)
+    do val = 1, 7
+        outprimes = 0
+        call find_factors(data(val), outprimes, count)
+        minim = minval(outprimes(1:count))
+        if (minim > largest_factor) then
+            largest_factor = minim
+            largest = data(val)
+        end if
+        write(*, fmt = '(A7,i0,A2,i12,100i12)') 'Thread ', OMP_GET_THREAD_NUM(), ': ', data(val), outprimes(1:count)
+    end do
+    !$omp end parallel do
+
+    write(*, fmt = '(i0,A26,i0)') largest, ' have the Largest factor: ', largest_factor
+
+    return
+
+contains
+
+    subroutine find_factors(n, d, count)
+        integer(int64), intent(in) :: n
+        integer(int64), dimension(:), intent(out) :: d
+        integer(int16), intent(out) :: count
+        integer(int16) :: i
+        integer(int64) :: div, next, rest
+
+        i = 1
+        div = 2; next = 3; rest = n
+
+        do while (rest /= 1)
+            do while (mod(rest, div) == 0)
+                d(i) = div
+                i = i + 1
+                rest = rest / div
+            end do
+            div = next
+            next = next + 2
+        end do
+        count = i - 1
+    end subroutine find_factors
+
+end program Primes