On Tue, 2019-10-01 at 12:52 +0200, Felix Fietkau wrote:
>
> Might be useful, yes. The main issue here is that the period / window
> size has to be hardcoded through the coefficient values, unless we find
> a way to do floating point math, including exp() and cos() at compile
> time, including conversion to fixed point.
Works fine for me?
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#define E(x) ((int)(exp(x) * (1<<20)))
#define C(x) ((int)(cos(x) * (1<<20)))
int main()
{
int e2 = E(2);
int c2 = C(2);
printf("e2: %d\n", e2);
printf("whole: %d frac: %d\n", e2 >> 20, e2 & ((1 << 20) - 1));
printf("c2: %d\n", c2);
printf("sign: %s whole: %d frac: %d\n", c2 < 0 ? "-" : "", abs(c2) >> 20, abs(c2) & ((1 << 20) - 1));
}
objdump -dr test:
[...]
0000000000401040 <main>:
401040: 48 83 ec 08 sub $0x8,%rsp
401044: be 92 39 76 00 mov $0x763992,%esi // exp(2) * (1<<20)
401049: bf 10 20 40 00 mov $0x402010,%edi
40104e: 31 c0 xor %eax,%eax
401050: e8 db ff ff ff callq 401030 <printf@plt>
401055: ba 92 39 06 00 mov $0x63992,%edx
40105a: be 07 00 00 00 mov $0x7,%esi
40105f: 31 c0 xor %eax,%eax
401061: bf 2b 20 40 00 mov $0x40202b,%edi
401066: e8 c5 ff ff ff callq 401030 <printf@plt>
40106b: be 77 57 f9 ff mov $0xfff95777,%esi
401070: bf 18 20 40 00 mov $0x402018,%edi
401075: 31 c0 xor %eax,%eax
401077: e8 b4 ff ff ff callq 401030 <printf@plt>
40107c: b9 89 a8 06 00 mov $0x6a889,%ecx // cos(2) * (1<<20)
401081: 31 d2 xor %edx,%edx
401083: 31 c0 xor %eax,%eax
401085: be 20 20 40 00 mov $0x402020,%esi
40108a: bf 22 20 40 00 mov $0x402022,%edi
40108f: e8 9c ff ff ff callq 401030 <printf@plt>
[...]
johannes
