Frederic Bouvier:

[simgear.git] / simgear / math / fastmath.hxx

diff --git a/simgear/math/fastmath.hxx b/simgear/math/fastmath.hxx
index b2b5595ad0d6f472392152ef0b74c9cc7f0e9364..288d3444145a54f99c4ba860f533cc26dde5cd96 100644 (file)
--- a/simgear/math/fastmath.hxx
+++ b/simgear/math/fastmath.hxx
@@ -25,15 +25,93 @@
 # error This library requires C++
 #endif
 
-
+#ifdef _MSC_VER
+#define  _USE_MATH_DEFINES
+#endif
 #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);
+double fast_exp2(const double val);
+
+float fast_pow(const float val1, const float val2);
+float fast_log2(const float cal);
+float fast_root(const float f, const int n);
+
+float _fast_pow2(const float cal);
+float _fast_log2(const float val);
+
+float fast_sin(const float val);
+float fast_cos(const float val);
+float fast_tan(const float val);
+float fast_asin(const float val);
+float fast_acos(const float val);
+float fast_atan(const float 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);
+}
+
+
+/**
+ * This function is about twice as fast as the system pow(x,y) function
+ */
+inline float fast_pow(const float val1, const float val2)
+{
+   return _fast_pow2(val2 * _fast_log2(val1));
+}
+
+
+/*
+ * Haven't seen this elsewhere, probably because it is too obvious?
+ * Anyway, these functions are intended for 32-bit floating point numbers
+ * only and should work a bit faster than the regular ones.
+ */
+inline float fast_abs(float f)
+{
+    int i=((*(int*)&f)&0x7fffffff);
+    return (*(float*)&i);
+}
+
+inline float fast_neg(float f)
+{
+    int i=((*(int*)&f)^0x80000000);
+    return (*(float*)&i);
+}
+
+inline int fast_sgn(float f)
+{
+    return 1+(((*(int*)&f)>>31)<<1);
+}
 
 #endif // !_SG_FMATH_HXX