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Fix some problems

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This commit is contained in:
ehofman
2003-06-28 12:58:59 +00:00
parent 5d24be8c51
commit dcdf8a4d5c
3 changed files with 38 additions and 40 deletions
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33
simgear/math/fastmath.cxx
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@@ -47,46 +47,17 @@ double fast_exp(double val) {
}
double fast_log2 (double val)
{
int * const exp_ptr = reinterpret_cast <int *> (&val);
int x = *exp_ptr;
const int log_2 = ((x >> 23) & 255) - 128;
x &= ~(255 << 23);
x += 127 << 23;
*exp_ptr = x;
val = ((-1.0f/3) * val + 2) * val - 2.0f/3; // (1)
return (val + log_2);
}
/**
* This function is about 3 times faster than the system log() function
* and has an error of about 0.01%
*/
double fast_log (double val)
{
return (fast_log2 (val) * 0.69314718f);
}
double fast_log10 (double val)
{
return (fast_log (val) / fast_log (10));
}
/**
* While we're on the subject, someone might have use for these as well?
* Float Shift Left and Float Shift Right. Do what you want with this.
*/
void fast_BSL(double &x, register unsigned long shiftAmount) {
void fast_BSL(float &x, register unsigned long shiftAmount) {
*(unsigned long*)&x+=shiftAmount<<23;
}
void fast_BSR(double &x, register unsigned long shiftAmount) {
void fast_BSR(float &x, register unsigned long shiftAmount) {
*(unsigned long*)&x-=shiftAmount<<23;

40
simgear/math/fastmath.hxx
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@@ -28,12 +28,40 @@
#include <math.h>
double fast_exp(double y);
double fast_log(double val);
double fast_log2 (double val);
double fast_log10(double val);
void fast_BSL(double &x, register unsigned long shiftAmount);
void fast_BSR(double &x, register unsigned long shiftAmount);
double fast_exp(double val);
void fast_BSL(float &x, register unsigned long shiftAmount);
void fast_BSR(float &x, register unsigned long shiftAmount);
inline float fast_log2 (float val)
{
int * const exp_ptr = reinterpret_cast <int *> (&val);
int x = *exp_ptr;
const int log_2 = ((x >> 23) & 255) - 128;
x &= ~(255 << 23);
x += 127 << 23;
*exp_ptr = x;
val = ((-1.0f/3) * val + 2) * val - 2.0f/3; // (1)
return (val + log_2);
}
/**
* This function is about 3 times faster than the system log() function
* and has an error of about 0.01%
*/
inline float fast_log (const float &val)
{
return (fast_log2 (val) * 0.69314718f);
}
inline float fast_log10 (const float &val)
{
return (fast_log2(val) / 3.321928095f);
}
#endif // !_SG_FMATH_HXX

5
simgear/sound/sound.cxx
View File

@@ -32,7 +32,6 @@
#include <simgear/debug/logstream.hxx>
#include <simgear/props/condition.hxx>
#include <simgear/math/fastmath.hxx>
#include "sound.hxx"
@@ -42,8 +41,8 @@
static double _snd_inv(double v) { return (v == 0) ? 1e99 : 1/v; }
static double _snd_abs(double v) { return (v >= 0) ? v : -v; }
static double _snd_sqrt(double v) { return (v < 0) ? sqrt(-v) : sqrt(v); }
static double _snd_log10(double v) { return (v < 1) ? 0 : fast_log10(v); }
static double _snd_log(double v) { return (v < 1) ? 0 : fast_log(v); }
static double _snd_log10(double v) { return (v < 1) ? 0 : log10(v); }
static double _snd_log(double v) { return (v < 1) ? 0 : log(v); }
// static double _snd_sqr(double v) { return v*v; }
// static double _snd_pow3(double v) { return v*v*v; }