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/* Test of log() function. Check some values and the monotone.
$Id: log-02.c,v 1.1 2007/02/05 21:35:58 dmix Exp $
*/
#define ULPMAX 6 /* Max possible error, "units at last place". */
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include "progmem.h"
union lofl_u {
long lo;
float fl;
};
volatile union lofl_u v = { .lo = 1 };
PROGMEM const struct { /* Table of test cases: x, log(x) */
union lofl_u x, z;
} t[] = {
{ { 0x00000001 }, { 0xc2ce8ed0 } },
{ { 0x00000002 }, { 0xc2cd2bec } },
{ { 0x00000003 }, { 0xc2cc5c53 } },
{ { 0x000000ff }, { 0xc2c379af } },
{ { 0x00000100 }, { 0xc2c377ae } },
{ { 0x00000101 }, { 0xc2c375af } },
{ { 0x0000ffff }, { 0xc2b8608f } },
{ { 0x00010000 }, { 0xc2b8608d } },
{ { 0x00010001 }, { 0xc2b8608b } },
{ { 0x007fffff }, { 0xc2aeac50 } },
{ { 0x00800000 }, { 0xc2aeac50 } },
{ { 0x00800001 }, { 0xc2aeac50 } },
/* 0.5 */
{ { 0x3effffff }, { 0xbf317219 } },
{ { 0x3f000000 }, { 0xbf317218 } },
{ { 0x3f000001 }, { 0xbf317216 } },
/* 1.0 */
{ { 0x3f7ffffe }, { 0xb4000001 } },
{ { 0x3f7fffff }, { 0xb3800000 } },
{ { 0x3f800000 }, { 0x00000000 } },
{ { 0x3f800001 }, { 0x33ffffff } },
{ { 0x3f800002 }, { 0x347ffffe } },
/* fraction 0x0.98 -- switch between tables */
{ { 0x3f97fffe }, { 0x3e2ff976 } },
{ { 0x3f97ffff }, { 0x3e2ff97d } },
{ { 0x3f980000 }, { 0x3e2ff984 } },
{ { 0x3f980001 }, { 0x3e2ff98a } },
/* fraction 0x0.E0 -- switch between tables */
{ { 0x3fdffffe }, { 0x3f0f42f9 } },
{ { 0x3fdfffff }, { 0x3f0f42fa } },
{ { 0x3fe00000 }, { 0x3f0f42fb } },
{ { 0x3fe00001 }, { 0x3f0f42fc } },
/* 2.0 */
{ { 0x3fffffff }, { 0x3f317217 } },
{ { 0x40000000 }, { 0x3f317218 } },
{ { 0x40000001 }, { 0x3f31721a } },
{ { 0x7f7ffffd }, { 0x42b17218 } },
{ { 0x7f7ffffe }, { 0x42b17218 } },
{ { 0x7f7fffff }, { 0x42b17218 } },
};
void x_exit (int index)
{
#ifndef __AVR__
fprintf (stderr, "t[%d]: %#lx\n", index - 1, v.lo);
#endif
exit (index ? index : -1);
}
int main ()
{
union lofl_u x, z, v1;
int i;
v.fl = -INFINITY;
for (i = 0; i < (int) (sizeof(t) / sizeof(t[0])); i++) {
x.lo = pgm_read_dword (& t[i].x);
z.lo = pgm_read_dword (& t[i].z);
v1.fl = log (x.fl);
if ( ((v1.lo ^ z.lo) & 0x80000000) /* signbit(v1) != signbit(z) */
|| labs (v1.lo - z.lo) > ULPMAX
|| v1.fl < v.fl)
{
v = v1;
x_exit (i+1);
}
v = v1;
}
return 0;
}
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