Fortran Wiki
sum

Description

Adds the elements of array along dimension dim if the corresponding element in mask is true.

Standard

Fortran 95 and later

Class

Transformational function

Syntax

result = sum(array[, mask])
result = sum(array, dim[, mask])

Arguments

array - Shall be an array of type integer, real or complex.
dim - (Optional) shall be a scalar of type integer with a value in the range from 1 to n, where n equals the rank of array.
mask - (Optional) shall be of type logical and either be a scalar or an array of the same shape as array.

Return value

The result is of the same type as array.

If dim is absent, a scalar with the sum of all elements in array is returned. Otherwise, an array of rank n-1, where n equals the rank of array,and a shape similar to that of array with dimension dim dropped is returned.

Example

program test_sum
  integer :: x(5) = (/ 1, 2, 3, 4 ,5 /)
  print *, sum(x)                        ! all elements, sum = 15
  print *, sum(x, mask=mod(x, 2)==1)     ! odd elements, sum = 9
end program

Fortran Wiki sum