Practical Fortran

Dot Product

Built-in Reduction

dot_product multiplies two same-shape arrays element-wise and sums the result.

Program

Play the program to compute the dot product of two real vectors.

dot_product.f90 
program dot_product_demo
    implicit none
    real :: x(3), y(3)
    real :: d
    x = [1.0, 2.0, 3.0]
    y = [4.0, 5.0, 6.0]
    d = dot_product(x, y)
    print '(F0.1)', d
end program dot_product_demo
dot_product `dot_product(x, y)` returns `sum(x * y)` for vectors.
real array `real :: x(3)` declares a length-3 real vector.
F0.1 `F0.1` prints a real with one decimal and no extra width.