Re: [Numpydiscussion] How to speed up this function?
You can speed it up easily by avoiding the loop. The main idea is to replace the indexing of the type [i+1,j], [i1,j], [i,j+1], [i,j1] by the appropriate slicing. For example for i in xrange(1,n): for j in xrange(1,m) a[i,j] = b[i1,j] + c[i,j+1] can be replaced by a[1:,:1] = b[:1] + c[:,1:] Nadav. Original Message From: numpydiscussionbounces@scipy.org [mailto:numpydiscussionbounces@scipy.org] On Behalf Of fsenkel@verizon.net Sent: Monday, December 04, 2006 05:28 To: numpydiscussion@scipy.org Subject: [Numpydiscussion] How to speed up this function? Hello, I'm taking a CFD class, one of the codes I wrote runs very slow. When I look at hotshot is says the function below is the problem. Since this is an explicit step, the for loops are only traversed once, so I think it's caused by memory usage, but I'm not sure if it's the local variables or the loop? I can vectorize the inner loop, would declaring the data structures in the calling routine and passing them in be a better idea than using local storage? I'm new at python and numpy, I need to look at how to get profiling information for the lines within a function. Thank you, Frank PS I tried to post this via google groups, but it didn't seem to go through, sorry if it ends up as multiple postings def findw(wnext,wprior,phiprior,uprior,vprior): #format here is x[i,j] where i's are rows, j's columns, use flipud() to get the #print out consistent with the spacial updown directions #assign local names that are more #inline with the class notation w = wprior phi = phiprior u = uprior v = vprior #three of the BC are known so just set them #symetry plane wnext[0,0:gcols] = 0.0 #upper wall wnext[gN,0:gcols] = 2.0/gdy**2 * (phi[gN,0:gcols]  phi[gN1,0:gcols]) #inlet, off the walls wnext[1:grows1,0] = 0.0 upos = where(u>0) vpos = where(v>0) Sx = ones_like(u) Sx[upos] = 0.0 Sy = ones_like(v) Sy[vpos] = 0.0 uw = u*w vw = v*w #interior nodes for j in range(1,gasizej1): for i in range(1,gasizei1): wnext[i,j] =( w[i,j] + gnu*gdt/gdx**2 * (w[i,j1]  2.0*w[i,j] + w[i,j+1]) + gnu*gdt/gdy**2 * (w[i1,j]  2.0*w[i,j] + w[i+1,j])  (1.0  Sx[i,j]) * gdt/gdx * (uw[i,j]  uw[i,j1])  Sx[i,j] * gdt/gdx * (uw[i,j+1]  uw[i,j])  (1.0  Sy[i,j]) * gdt/gdy * (vw[i,j]  vw[i1,j])  Sy[i,j] * gdt/gdy * (vw[i+1,j]  vw[i,j]) ) ## print "***wnext****" ## print "i: ", i, "j: ", j, "wnext[i,j]: ", wnext[i,j] #final BC at outlet, off walls wnext[1:grows1,gM] = wnext[1:grows1,gM1] _______________________________________________ Numpydiscussion mailing list Numpydiscussion@scipy.org http://projects.scipy.org/mailman/listinfo/numpydiscussion
participants (1)

Nadav Horesh