title: Unending Python Program which does not show results or errors
body: <p>I am trying to do a double integration which has matrices. When I run it, it does not show any result. Neither is it showing any errors. It just runs endlessly without any output. I don't think an infinite loop can be the problem as I am using 'for'. Is it because there are four 'for' loops and the system is incapable of doing it? Following is my code :</p>
  
  <pre><code>    f = np.zeros((1024,90))  
  
      D = 0.28                
      h = np.zeros(1024)
      h[0:512] = np.linspace(0,1,512)
      h[513:] = np.linspace(1,0,511) 
  
      for r in range(0,1024) :
        for phi in range(0,90) :
          for b in range(0,360) :
            for s in range(0,1024) :
              U = (D + r*sin(b-phi))/D
              l = math.pow(U,-2)
              k = D/(math.pow((math.pow(D,2)+math.pow(s,2)),0.5))   
              f[r,phi] = 0.5*l*k*q[s,b]*h[s]
  
      I =np.zeros((725,725))
  
      for x in range(0,725) :
        for y in range(0,725) :
          r = math.pow(x,2)+math.pow(y,2)
          phi = math.degrees(math.atan(y/x))
          I[x,y] = f[r,phi]
  
      I8 = (((I - I.min()) / (I.max() - I.min())) * 255.9).astype(np.uint8)
      img = Image.fromarray(I8)
      img.save("Fanbeamreconstruction.png")
      im = Image.open("Fanbeamreconstruction.png")
      im.show()
  </code></pre>
  
  <p>Any help or suggestions will be appreciated. Thank you!</p>