diff options
| author | qiuyiuestc <[email protected]> | 2010-09-25 16:37:31 +0000 |
|---|---|---|
| committer | qiuyiuestc <[email protected]> | 2010-09-25 16:37:31 +0000 |
| commit | af13fb68356081a25bdac94bdafa40bf0501d409 (patch) | |
| tree | 508c0d1a0af32c2ebee95e144742de695bcf80d5 /components/libc | |
| parent | 5a8f34e46f0c8d6ff8a0384c06a061b7bde5ea79 (diff) | |
add sin, cos implementation
git-svn-id: https://rt-thread.googlecode.com/svn/trunk@949 bbd45198-f89e-11dd-88c7-29a3b14d5316
Diffstat (limited to 'components/libc')
| -rw-r--r-- | components/libc/minilibc/math.c | 167 |
1 files changed, 162 insertions, 5 deletions
diff --git a/components/libc/minilibc/math.c b/components/libc/minilibc/math.c index d86abe5877..8fdce039e5 100644 --- a/components/libc/minilibc/math.c +++ b/components/libc/minilibc/math.c @@ -1,12 +1,169 @@ #include <math.h>
-/* Fix me */
-double sin(double x)
+/*
+ * COPYRIGHT: See COPYING in the top level directory
+ * PROJECT: ReactOS CRT
+ * FILE: lib/crt/math/cos.c
+ * PURPOSE: Generic C Implementation of cos
+ * PROGRAMMER: Timo Kreuzer ([email protected])
+ */
+
+#define PRECISION 9
+#define M_PI 3.141592653589793238462643
+
+static double cos_off_tbl[] = {0.0, -M_PI/2., 0, -M_PI/2.};
+static double cos_sign_tbl[] = {1,-1,-1,1};
+
+static double sin_off_tbl[] = {0.0, -M_PI/2., 0, -M_PI/2.};
+static double sin_sign_tbl[] = {1,-1,-1,1};
+
+double sin(double x)
{
- #warning sin function not supported for this platform
+ int quadrant;
+ double x2, result;
+
+ /* Calculate the quadrant */
+ quadrant = x * (2./M_PI);
+
+ /* Get offset inside quadrant */
+ x = x - quadrant * (M_PI/2.);
+
+ /* Normalize quadrant to [0..3] */
+ quadrant = (quadrant - 1) & 0x3;
+
+ /* Fixup value for the generic function */
+ x += sin_off_tbl[quadrant];
+
+ /* Calculate the negative of the square of x */
+ x2 = - (x * x);
+
+ /* This is an unrolled taylor series using <PRECISION> iterations
+ * Example with 4 iterations:
+ * result = 1 - x^2/2! + x^4/4! - x^6/6! + x^8/8!
+ * To save multiplications and to keep the precision high, it's performed
+ * like this:
+ * result = 1 - x^2 * (1/2! - x^2 * (1/4! - x^2 * (1/6! - x^2 * (1/8!))))
+ */
+
+ /* Start with 0, compiler will optimize this away */
+ result = 0;
+
+#if (PRECISION >= 10)
+ result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12*13*14*15*16*17*18*19*20);
+ result *= x2;
+#endif
+#if (PRECISION >= 9)
+ result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12*13*14*15*16*17*18);
+ result *= x2;
+#endif
+#if (PRECISION >= 8)
+ result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12*13*14*15*16);
+ result *= x2;
+#endif
+#if (PRECISION >= 7)
+ result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12*13*14);
+ result *= x2;
+#endif
+#if (PRECISION >= 6)
+ result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12);
+ result *= x2;
+#endif
+#if (PRECISION >= 5)
+ result += 1./(1.*2*3*4*5*6*7*8*9*10);
+ result *= x2;
+#endif
+ result += 1./(1.*2*3*4*5*6*7*8);
+ result *= x2;
+
+ result += 1./(1.*2*3*4*5*6);
+ result *= x2;
+
+ result += 1./(1.*2*3*4);
+ result *= x2;
+
+ result += 1./(1.*2);
+ result *= x2;
+
+ result += 1;
+
+ /* Apply correct sign */
+ result *= sin_sign_tbl[quadrant];
+
+ return result;
}
-double cos(double x)
+double cos(double x)
{
- #warning cos function not supported for this platform
+ int quadrant;
+ double x2, result;
+
+ /* Calculate the quadrant */
+ quadrant = x * (2./M_PI);
+
+ /* Get offset inside quadrant */
+ x = x - quadrant * (M_PI/2.);
+
+ /* Normalize quadrant to [0..3] */
+ quadrant = quadrant & 0x3;
+
+ /* Fixup value for the generic function */
+ x += cos_off_tbl[quadrant];
+
+ /* Calculate the negative of the square of x */
+ x2 = - (x * x);
+
+ /* This is an unrolled taylor series using <PRECISION> iterations
+ * Example with 4 iterations:
+ * result = 1 - x^2/2! + x^4/4! - x^6/6! + x^8/8!
+ * To save multiplications and to keep the precision high, it's performed
+ * like this:
+ * result = 1 - x^2 * (1/2! - x^2 * (1/4! - x^2 * (1/6! - x^2 * (1/8!))))
+ */
+
+ /* Start with 0, compiler will optimize this away */
+ result = 0;
+
+#if (PRECISION >= 10)
+ result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12*13*14*15*16*17*18*19*20);
+ result *= x2;
+#endif
+#if (PRECISION >= 9)
+ result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12*13*14*15*16*17*18);
+ result *= x2;
+#endif
+#if (PRECISION >= 8)
+ result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12*13*14*15*16);
+ result *= x2;
+#endif
+#if (PRECISION >= 7)
+ result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12*13*14);
+ result *= x2;
+#endif
+#if (PRECISION >= 6)
+ result += 1./(1.*2*3*4*5*6*7*8*9*10*11*12);
+ result *= x2;
+#endif
+#if (PRECISION >= 5)
+ result += 1./(1.*2*3*4*5*6*7*8*9*10);
+ result *= x2;
+#endif
+ result += 1./(1.*2*3*4*5*6*7*8);
+ result *= x2;
+
+ result += 1./(1.*2*3*4*5*6);
+ result *= x2;
+
+ result += 1./(1.*2*3*4);
+ result *= x2;
+
+ result += 1./(1.*2);
+ result *= x2;
+
+ result += 1;
+
+ /* Apply correct sign */
+ result *= cos_sign_tbl[quadrant];
+
+ return result;
}
+
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