On Sat, Apr 19, 2008 at 09:46:38AM +0200, Jeremie Le Hen wrote:

Most numerical applications, that I'm familiar with, tend to contain nested loops that make calls to functions in libm. Simple example in one of my codes is a 3 deep loop that computes what is known as the thermal dose.

for (k = 0; k < kmax; k++) for (j = 0; j < jmax; j++) for (i = 0; i < imax; i++) td += exp(a * b[k][j][i])

Now, put the above loops inside a time loop with n time steps. exp() will be called kmax*jmax*imax*n times where this product can be quite large (order of 5e11). Any overhead caused by PP will increase the simulation time. A 1% increase in time is probably tolerable, but a 10% increase would be detrimental to simulations that takes days to complete (yes, I have a few that run that long).

I'll see if I can get you some numbers this weekend.