Extreme Programming - Optimize these 2 lines of code!!

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Optimize these 2 lines of code!!

Tan Thuan Seah

2004-05-24, 6:35 am

Hi all,

I am working on an assignment and i hope to optimize the following two
lines of code for a Ultrasparc II machine. The code is running in a loop for
about 100000 iterations.

dist2 = a*a + b*b + c*c;
dist = sqrt(dist2);
d = 12.0/pow(dist, 14.0) - 12.0/pow(dist, 8..0);
pe+= 1.0/pow(dist, 12) - 2.0/pow(dist, 6.0);

i have change it to:

dist2 = a*a+b*b+c*c;
e = dist2 * dist2 *dist2; // to get the same as pow(dist, 6.0)
f = e * e * dist2; // to get the same as pow(dist, 14.0)
d = (12.0 - 12.0*e)/f; // most expensive computation in the loop
<-- the 2 lines of code starts here
pe += (1.0 - 2.0*e)/(e*e) // next most expensive computation in the loop

But this is still not producing the speed i am expecting. What else can i do
to optimise? Thx for any hints and advice.

Thuan Seah

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