Monday, April 23, 2012

sincos()

If you are computing both the sine and cosine of an angle, then you will be twice as quick if you call sincos() than if you call cos() and sin() independently:

#include 

int main()
{
  double a,b,c;
  a=1.0;
  for (int i=0;i<100000000;i++) { b=sin(a); c=cos(a); }
}

$ cc -O sc.c -lm
$ timex ./a.out
real          19.13

vs

#include 

int main()
{
  double a,b,c;
  a=1.0;
  for (int i=0;i<100000000;i++) { sincos(a,&b,&c); }
}
$ cc -O sc.c -lm
$ timex ./a.out
real           9.80