/* goldstein-price.c:

The Golstein-Price Optimization test function

Written 2018 by Edwin A. Suominen as an example for the "ade" python

package. This C code file is dedicated to the public domain.

Compile with

"gcc -Wall -o goldstein-price goldstein-price.c"

If you don't have gcc, install it first with

"sudo apt install gcc"

Provide X and Y float values via STDIN, separated by a space and

ending with a newline. Prints result float value on STDOUT ending

with a newline.

Enter "99999 99999" as X and Y and the overflowing result will

terminate the program. Or just send Ctrl+C.

*/

#include <stdio.h>

#include <math.h>

float gp(float x, float y) {

// The Goldstein-Price function

float z, result;

z = x + y + 1;

z *= z;

z *= 19 - 14*x + 3*x*x - 14*y + 6*x*y + 3*y*y;

z += 1;

result = z;

z = 2*x - 3*y;

z *= z;

z *= 18 - 32*x + 12*x*x + 48*y - 36*x*y + 27*y*y;

z += 30;

result *= z;

return result;

}

int main() {

// Runs the Goldstein-Price function for each pair of float values

// received via STDIN, until there is an overflowing result

float x, y, result;

while (1) {

scanf("%f %f", &x, &y);

result = gp(x, y);

if (isinf(result))

break;

printf("%f\n", result);

}

return 0;

}