Initial import

git-svn-id: http://moon:8086/svn/software/trunk/libsrc/fast_trig@1 b431acfa-c32f-4a4a-93f1-934dc6c82436

fast_trig.c

@@ -0,0 +1,157 @@
+// --------------------------------------------------------------
+#define	SINE_TABLE_START_INDEX		2		
+#define	COSINE_TABLE_START_INDEX	2		
+#define	EXP_TABLE_START_INDEX		0
+
+// --------------------------------------------------------------
+#include <math.h>
+#include "synth_defs.h"
+
+// Taylor series coefficent for cos(pi*x)
+// In this table x is premultiplied with pi!
+static const synth_float_t _sg_cos_pmpi_lut[] = 
+{
+    1.92957430940392e-003,
+   -25.8068913900141e-003,
+    235.330630358893e-003,
+   -1.33526276885459e+000,
+    4.05871212641677e+000,
+   -4.93480220054468e+000,
+    1.00000000000000e+000
+
+};
+
+// Taylor series coefficent for sin(x)
+static const synth_float_t _sg_sin_lut[] = 
+{
+	 1.605904383682161e-010,
+	-2.505210838544172e-008,
+	 2.755731922398589e-006,
+	-1.984126984126984e-004,
+	 8.333333333333333e-003,
+	-1.666666666666667e-001,
+	 1.000000000000000e+000
+};
+
+// Taylor series coefficent for sin(x)
+static const synth_float_t _sg_cos_lut[] = 
+{
+	 2.087675698786810e-009,
+	-2.755731922398589e-007,
+	 2.480158730158730e-005,
+	-1.388888888888889e-003,
+	 4.166666666666666e-002,
+	-5.000000000000000e-001,
+	 1.000000000000000e+000
+};
+
+// Taylor series coefficent for sin(x)
+static const synth_float_t _sg_exp_lut[] = 
+{
+	1.984126984126984e-004,
+	1.388888888888889e-003,
+	8.333333333333333e-003,
+	4.166666666666666e-002,
+	1.666666666666667e-001,
+	5.000000000000000e-001,
+	1.000000000000000e+000,
+	1.000000000000000e+000
+};
+
+// --------------------------------------------------------------
+// Exported functions
+// --------------------------------------------------------------
+// Cos (pi*x)
+synth_float_t FastTrig_cos_premult_pi(synth_float_t x)
+{
+	int i, yneg;
+	synth_float_t y, xx;
+
+	yneg = 0;
+
+	if (x < 0)
+		x = -x;
+
+    if (x > (synth_float_t)0.5)
+	{
+        if (x > (synth_float_t)1.5)
+		{
+            x = (synth_float_t)2. - x;
+		}
+        else
+		{
+            x = (synth_float_t)1. - x;
+            yneg = 1;
+		}
+	}
+	xx = x*x;
+	y = _sg_cos_pmpi_lut[0];
+	
+	for (i=1; i < sizeof(_sg_cos_pmpi_lut)/sizeof(synth_float_t); i++)
+		y = y * xx + _sg_cos_pmpi_lut[i];
+	
+	if (yneg)
+		y = -y;
+
+	return y;
+}
+
+// sin (x)
+// Best in range -0.5*pi .. +0.5*pi
+synth_float_t FastTrig_sin(synth_float_t x)
+{
+	int i = SINE_TABLE_START_INDEX;
+	synth_float_t xx, y;
+
+	xx = x*x;
+	y = _sg_sin_lut[i++];
+	
+	for (i=i; i < sizeof(_sg_sin_lut)/sizeof(synth_float_t); i++)
+		y = y * xx + _sg_sin_lut[i];
+
+	return y * x;
+}
+
+// cos (x)
+// Best in range -0.5*pi .. +0.5*pi
+synth_float_t FastTrig_cos(synth_float_t x)
+{
+	int i = COSINE_TABLE_START_INDEX;
+	synth_float_t xx, y;
+
+	xx = x*x;
+	y = _sg_cos_lut[i++];
+	
+	for (i=i; i < sizeof(_sg_cos_lut)/sizeof(synth_float_t); i++)
+		y = y * xx + _sg_cos_lut[i];
+
+	return y;
+}
+
+// exp (x)
+synth_float_t FastTrig_exp(synth_float_t x)
+{
+	int i = EXP_TABLE_START_INDEX;
+	synth_float_t y;
+
+	y = _sg_exp_lut[i++];
+	
+	for (i=i; i < sizeof(_sg_exp_lut)/sizeof(synth_float_t); i++)
+		y = y * x + _sg_exp_lut[i];
+
+	return y;
+}
+
+// exp (x) - 1
+synth_float_t FastTrig_exp_minus_1(synth_float_t x)
+{
+	int i = EXP_TABLE_START_INDEX;
+	synth_float_t y;
+
+	y = _sg_exp_lut[i++];
+	
+	for (i=i; i < sizeof(_sg_exp_lut)/sizeof(synth_float_t)-1; i++)
+		y = y * x + _sg_exp_lut[i];
+
+	return y*x;
+}

fast_trig.h

@@ -0,0 +1,31 @@
+// --------------------------------------------------------------
+#ifndef _FAST_TRIG_H_
+#define	_FAST_TRIG_H_
+
+#include "synth_types.h"
+
+// --------------------------------------------------------------
+// Types
+// --------------------------------------------------------------
+
+// --------------------------------------------------------------
+#if defined(__cplusplus)
+extern "C" {
+#endif
+
+// --------------------------------------------------------------
+// Exported functions
+// --------------------------------------------------------------
+synth_float_t FastTrig_cos_premult_pi(synth_float_t x);
+synth_float_t FastTrig_sin(synth_float_t x);
+synth_float_t FastTrig_cos(synth_float_t x);
+synth_float_t FastTrig_exp(synth_float_t x);
+synth_float_t FastTrig_exp_minus_1(synth_float_t x);
+
+#if defined(__cplusplus)
+}
+
+#endif
+// --------------------------------------------------------------
+
+#endif // _FAST_TRIG_H_