title: stucked do loop in fortran
body: <p>i just make easy equation(gaussian-plume eq.)
  the goal is Concentration values based on x, y, z distribution
  but the loop is stucked at just first step what's the problem?
  here's my code</p>
  <pre><code>  PROGRAM plume
    IMPLICIT NONE
    REAL,PARAMETER :: pi=3.141592, q=1000, u=5, t=10,
   &amp;                  kx=1, ky=1, kz=1
    REAL :: d, dx, dy, dz, f1, f2, C
    INTEGER :: x, y, z
  
    OPEN(10, file='./results/plume.txt')
  
    WRITE(10,'(3(A4),2(x,A50))') &quot;x&quot;,&quot;y&quot;,&quot;z&quot;, &quot;f2&quot;, &quot;C&quot;
  
    dy = dx
    dz = dx
    dx = (2 * kx * t)
  
    PRINT*, &quot;f1=&quot;, f1(q,pi,u,dx)
  
    DO x = 0, 1000, 10
     DO y = -500,500,10 
      DO z = 0,500,10 
       f2 = exp( -(1/2) * ( ( (y**2.) + (z**2.) ) / dx ) ) 
       C = f1(q,pi,u,dx) * f2
       WRITE(10,'(3(I4),(x,2(F50.48)))') x, y, z, f2, C
      END DO
     END DO
    END DO
       
  
    END PROGRAM
  
  
    FUNCTION f1(q,pi,u,dx)
    IMPLICIT NONE
    REAL :: q, pi, u
    REAL :: f1, dx
     f1 = q / (2 * pi * u * dx)
    END FUNCTION f1
  </code></pre>