Add 2nd optimization scheme

 gcc  -O3  cost.c -lm
$ ./a.out 
default sum 0.124374 0.000000 
multi sum 0.139044 0.000000 
pow 2 sum 0.140517 0.000000 
pow 2.1 sum 1.235733 0.000000 
exp sum 5.393549 100000000.000000 
sin sum 5.419529 0.000000 
regular eqn sum 1.411861 0.000000 
expanded eqn sum 0.328787 0.000000 
optimized eqn sum 0.261804 0.000000 
2nd optimized eqn sum 0.247991 0.000000

Author: hpjeonGIT

math_test.c

@@ -134,6 +134,20 @@ int main()
   e_time = clock();
   printf("optimized eqn sum %f %f \n", (e_time - s_time)/(double) CLOCKS_PER_SEC, x);
 
+  // 2nd optimized equation
+  s_time = clock();
+  x = 0.0;
+  for (i=0;i<nmax;i++){
+    for (j=0;j<nmax;j++) {
+      dx = abs(v1[i] - v2[j]);
+      x += c*dx;
+      dx = dx*dx;
+      x += dx*(b + dx*a);
+    }
+  }
+  e_time = clock();
+  printf("2nd optimized eqn sum %f %f \n", (e_time - s_time)/(double) CLOCKS_PER_SEC, x);
+
   free(v1);
   free(v2);
   return 0;