Jonathan L Dubois (dubois@bec.physics.udel.edu)
Sat, 28 Nov 1998 14:28:39 -0500 (EST)
On Sat, 28 Nov 1998, Kazushige Goto wrote:
> Actually, sqrt routine is pretty "sparse" because of calculation
> dependencies. If it's possible to store temporary array in the lump,
> you may use my sqrtv(vectorlized sqrt) routine. This sqrtv routine is
> 5 times faster than normal sqrt routine. But you showed only kernel
> routine, so I do not know whether it's possible to be faster or not.
> In this case, it's important "how to call" r12 routine.
>
> So, you should show the routines which call r12 routine.
The loop which calls r12 is shown below.
N could be as large as 10000
int find_jastrow(double *result,int j,struct coord *q,double r[3],double b){
int i;
double rij;
double tmp;
tmp = 1.0;
if(b>0){
for(i=0;i < N;i++){
if(i!=j){
r12(&rij,q[i].x,r);
if(rij > b){
tmp *= (1.0 - b/rij);
}
else{
*result = 0;
return 0;
}
}
}
}
*result = tmp;
return 1;
}
void r12(double *rij,double *x1,double *x2){
int i;
double tmp1,tmp2;
tmp2 = 0;
for(i=0;i<3;i++){
tmp1 = x1[i]-x2[i];
tmp2 += tmp1*tmp1;
}
tmp2 = sqrt(tmp2);
*rij = tmp2;
}
The only problem I foresee with doing all the sqrts in r12 at once is that
I occasionally get some computational savings when (rij <= b) The
probability of this occurring is usually fairly low but it increases with
N and is not easily predicted ahead of time. It will also probably
require some restructuring since q[i] is an array of structures which
contain information other than the 3vectors of interest here.
Jonathan DuBois
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