trigtest.c

/* From:
https://community.intel.com/t5/Intel-C-Compiler/What-is-wrong-in-fsin-opcode/m-p/926872

My blog post on the subject: https://pergelator.blogspot.com/2022/06/computer-math.html

Set text editor tab width to 4

Terminal log of this test:

	$ cc trigtest.c -lm -DTEST=1
	$ time ./a.out
	2.356194

	real	0m1.046s
	user	0m1.044s
	sys	0m0.000s


	$ cc trigtest.c -lm -DTEST=2
	$ time ./a.out
	3.141593

	real	0m8.666s
	user	0m8.640s
	sys	0m0.000s

The important thing to notice is that the TEST 2 takes roughly 8 times longer than TEST 1
even though it only makes one call to the trig library.

*/

#ifndef TEST
	#error Define TEST as 1 or 2 (-DTEST=1 or -DTEST=2)
#elif TEST!=1 && TEST!=2
	#error Define TEST as 1 or 2 (-DTEST=1 or -DTEST=2)
#endif

#include <stdio.h>
#include <math.h>

int main()
{
	double x=1;
	double y;
	for(int i=1;i<20000000;i++)
	{
		y=sin(x);
#if TEST==1
		y+=cos(x);
#endif
		x+=y;
	}
	printf("%f\n", x);
	return 0;
}