[postgis-users] Improving Performance

[David Blasby]

David Blasby wrote:

> We'll need to write a function that takes a BOX3D and converts it to a 
> BOX2DFLOAT.  The BOX2DFLOAT's xmin/ymin will have to be strictly less 
> than the BOX3D's xmin/ymin to ensure that all the queries work properly.

I looked this up -

// gcc test7.cpp -lm ; ./a.out

#include "stdio.h"
#include "math.h"

int main(int argC, char* argV[])
{

printf("doubles:\n");
     printf("%20.20lf\n", nextafter(1.0, 20.0));
     printf("%20.20lf\n", 1.0);
     printf("%20.20lf\n", nextafter(1.0, -20.0));

printf("floats:\n");
      printf("%20.20f\n", nextafterf(1.0, 20.0));
      printf("%20.20f\n", 1.0);
      printf("%20.20f\n", nextafterf(1.0, -20.0));
}


gives you:

doubles:
1.00000000000000022204
1.00000000000000000000
0.99999999999999988898
floats:
1.00000011920928955078
1.00000000000000000000
0.99999994039535522461