Vectorized and devectorized versions of the laplace benchmark now

give the same results (#1168)

test/perf2/laplace.jl

@@ -1,37 +1,28 @@
-function laplace{T}(u::Matrix{T}, dx2, dy2) 
-    uout = zeros(T, size(u)) 
-    for i = 2:size(u,1)-1 
-        for j = 2:size(u,2)-1 
-            uout[i,j] = ((u[i-1,j]+u[i+1,j])*dx2 + (u[i,j-1]+u[i,j+1])*dy2)/(2*(dx2+dy2)) 
-        end 
-    end 
-    return uout 
-end 
-
-function laplace_iter(u, dx, dy, Niter)
-    dx2 = dx^2
-    dy2 = dy^2
-    for i = 1:Niter 
-        u = laplace(u, dx2, dy2)
+function laplace_iter_devec(u, dx2, dy2, Niter, N)
+    uout = copy(u)
+    for iter = 1:Niter
+        for i = 2:N-1
+            for j = 2:N-1 
+                uout[i,j] = ( (u[i-1,j]+u[i+1,j])*dy2 + (u[i,j-1]+u[i,j+1])*dx2 ) * (1./(2*(dx2+dy2)))
+            end 
+        end
+        u, uout = uout, u
     end
     return u
 end 
 
 function laplace_devec()
     N = 150
-    u = zeros(N,N) 
+    u = zeros(N, N) 
     u[1,:] = 1 
     Niter = 2^10
-    dx = 0.1 
-    dy = 0.1
-    u = laplace_iter(u, dx, dy, Niter)
+    dx2 = dy2 = 0.1*0.1
+    u = laplace_iter_devec(u, dx2, dy2, Niter, N)
 end
 
-function laplace_iter_vec(u, dx, dy, Niter, N)
-    dx2 = dx*dx;
-    dy2 = dy*dy;
+function laplace_iter_vec(u, dx2, dy2, Niter, N)
     for i = 1:Niter
-        u[2:N-1, 2:N-1] = ((u[1:N-2, 2:N-1] + u[3:N, 2:N-1])*dy2 + (u[2:N-1,1:N-2] + u[2:N-1, 3:N])*dx2) * (1./ (2*(dx2+dy2)));
+        u[2:N-1, 2:N-1] = ((u[1:N-2, 2:N-1] + u[3:N, 2:N-1])*dy2 + (u[2:N-1,1:N-2] + u[2:N-1, 3:N])*dx2) * (1./ (2*(dx2+dy2)))
     end
     return u
 end
@@ -41,7 +32,6 @@ function laplace_vec()
     u = zeros(N,N) 
     u[1,:] = 1 
     Niter = 2^10 
-    dx = 0.1 
-    dy = 0.1
-    u = laplace_iter_vec(u, dx, dy, Niter, N)
+    dx2 = dy2 = 0.1*0.1
+    u = laplace_iter_vec(u, dx2, dy2, Niter, N)
 end