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Updated 32-bit divide, gained 1600% speed increase and an accuracy of 0.00065% (rather than 0.0035%) by multiplying by the reciprocal rather than using a divide algorithm.

This commit is contained in:
flatmush 2011-02-28 15:04:50 +00:00
parent ae58c98283
commit 047ab9fba0
1 changed files with 42 additions and 4 deletions
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46
libfixmath/fix16.c
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@ -97,7 +97,24 @@ fix16_t fix16_div(fix16_t inArg0, fix16_t inArg1) {
tempResult /= inArg1;
return tempResult;
#else
int32_t res = (inArg0 / inArg1) << 16;
int32_t rcp = (0xFFFFFFFF / inArg1);
int32_t rcp_hi = rcp >> 16;
uint32_t rcp_lo = rcp & 0xFFFF;
int32_t arg_hi = (inArg0 >> 16);
uint32_t arg_lo = (inArg0 & 0xFFFF);
int32_t res_hi = rcp_hi * arg_hi;
int32_t res_md = (rcp_hi * arg_lo) + (rcp_lo * arg_hi);
uint32_t res_lo = rcp_lo * arg_lo;
int32_t res = (res_hi << 16) + res_md + (res_lo >> 16);
#ifndef FIXMATH_NO_ROUNDING
res += ((res_lo >> 15) & 1);
#endif
return res;
/*int32_t res = (inArg0 / inArg1) << 16;
int32_t mod = inArg0 % inArg1;
uintptr_t i;
for(i = 0; i < 16; i++) {
@ -109,7 +126,7 @@ fix16_t fix16_div(fix16_t inArg0, fix16_t inArg1) {
if((mod << 1) / inArg1)
res++;
#endif
return res;
return res;*/
#endif
}
@ -132,7 +149,28 @@ fix16_t fix16_sdiv(fix16_t inArg0, fix16_t inArg1) {
return fix16_MAX;
return tempResult;
#else
int32_t res = (inArg0 / inArg1);
int32_t rcp = (0xFFFFFFFF / inArg1);
int32_t rcp_hi = rcp >> 16;
if(rcp_hi >= 32768)
return fix16_MAX;
if(rcp_hi < -32768)
return fix16_MIN;
uint32_t rcp_lo = rcp & 0xFFFF;
int32_t arg_hi = (inArg0 >> 16);
uint32_t arg_lo = (inArg0 & 0xFFFF);
int32_t res_hi = rcp_hi * arg_hi;
int32_t res_md = (rcp_hi * arg_lo) + (rcp_lo * arg_hi);
uint32_t res_lo = rcp_lo * arg_lo;
int32_t res = (res_hi << 16) + res_md + (res_lo >> 16);
#ifndef FIXMATH_NO_ROUNDING
res += ((res_lo >> 15) & 1);
#endif
return res;
/*int32_t res = (inArg0 / inArg1);
if((res < -32768) || (res >= 32768))
return (res < 0 ? fix16_MIN : fix16_MAX);
res <<= 16;
@ -147,7 +185,7 @@ fix16_t fix16_sdiv(fix16_t inArg0, fix16_t inArg1) {
if((mod << 1) / inArg1)
res++;
#endif
return res;
return res;*/
#endif
}