New submission from Ismael <ismaelgfk@gmail.com>: In the following code, the order of calls alters the performance. First case: running calc first, then calc_arr second: ismael@chaos:~/Escritorio$ ~/pypy/bin/pypy slow.py Section time: 0.865699052811 -- Calc Section time: 0.757493019104 -- Calc_arr So, here, best time for calc_arr is 0.75s. It doesn't matter if I run it 10 times, it still about that fast. Now, running calc_arr first and calc second: ismael@chaos:~/Escritorio$ ~/pypy/bin/pypy slow.py Section time: 0.400774002075 -- Calc_arr Section time: 1.53682088852 -- Calc The method that took 0.7s now takes 0.4! And the one that took 0.8s now takes 1.5! For comparison, PyPy latest (45351) is even worse: ismael@chaos:~/Escritorio$ ~/pypy/pypylatest/pypy-c-jit-45351-2630c86662b4-linux64/bin/pypy slow.py Section time: 0.940190792084 -- Calc Section time: 0.925091981888 -- Calc_arr ismael@chaos:~/Escritorio$ ~/pypy/pypylatest/pypy-c-jit-45351-2630c86662b4-linux64/bin/pypy slow.py Section time: 0.418694019318 -- Calc_arr Section time: 1.73908495903 -- Calc Code modified from http://technicaldiscovery.blogspot.com/2011/07/speeding-up-python-again.html class Timer(object): def __enter__(self): self.start = time.time() def __exit__(self, exc_type, exc_val, tb): print "Section time: ", time.time() - self.start import array import time dx = 0.1 dy = 0.1 dx2 = dx*dx dy2 = dy*dy def py_update(u,nx,ny): for i in xrange(1,nx-1): for j in xrange(1, ny-1): u[i][j] = ((u[i+1][j] + u[i-1][j]) * dy2 + (u[i][j+1] + u[i][j-1]) * dx2) / (2*(dx2+dy2)) def calc(N, Niter=100): u = [[0.0]*N for i in xrange(N)] for i in xrange(N): u[0][i] = 1.0 for i in range(Niter): py_update(u,N,N) return u def calc_arr(N, Niter=100): u = [array.array("d", [0.0])*N for i in xrange(N)] for i in xrange(N): u[0][i] = 1.0 for i in range(Niter): py_update(u,N,N) return u #Compare this: with Timer(): u = calc_arr(150,1000) with Timer(): u = calc(150,1000) #To this (comment the previous section): with Timer(): u = calc(150,1000) with Timer(): u = calc_arr(150,1000) ---------- messages: 2741 nosy: Ismael, pypy-issue priority: bug release: 1.5 status: unread title: Order of calls changes performance ________________________________________ PyPy bug tracker <tracker@bugs.pypy.org> <https://bugs.pypy.org/issue782> ________________________________________