1 files changed, 67 insertions, 0 deletions
diff --git a/src/math/s_cbrtf.c b/src/math/s_cbrtf.c
new file mode 100644
index 00000000..e7b46de7
--- /dev/null
+++ b/src/math/s_cbrtf.c
@@ -0,0 +1,67 @@
+/* s_cbrtf.c -- float version of s_cbrt.c.
+ * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
+ */
+
+/*
+ * ====================================================
+ * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
+ *
+ * Developed at SunPro, a Sun Microsystems, Inc. business.
+ * Permission to use, copy, modify, and distribute this
+ * software is freely granted, provided that this notice
+ * is preserved.
+ * ====================================================
+ */
+
+#include <math.h>
+#include "math_private.h"
+
+/* cbrtf(x)
+ * Return cube root of x
+ */
+static const unsigned
+        B1 = 709958130, /* B1 = (84+2/3-0.03306235651)*2**23 */
+        B2 = 642849266; /* B2 = (76+2/3-0.03306235651)*2**23 */
+
+static const float
+C =  5.4285717010e-01, /* 19/35     = 0x3f0af8b0 */
+D = -7.0530611277e-01, /* -864/1225 = 0xbf348ef1 */
+E =  1.4142856598e+00, /* 99/70     = 0x3fb50750 */
+F =  1.6071428061e+00, /* 45/28     = 0x3fcdb6db */
+G =  3.5714286566e-01; /* 5/14      = 0x3eb6db6e */
+
+float
+cbrtf(float x)
+{
+        float r,s,t;
+        int32_t hx;
+        uint32_t sign;
+        uint32_t high;
+
+        GET_FLOAT_WORD(hx,x);
+        sign=hx&0x80000000;             /* sign= sign(x) */
+        hx  ^=sign;
+        if(hx>=0x7f800000) return(x+x); /* cbrt(NaN,INF) is itself */
+        if(hx==0)
+            return(x);          /* cbrt(0) is itself */
+
+        SET_FLOAT_WORD(x,hx);   /* x <- |x| */
+    /* rough cbrt to 5 bits */
+        if(hx<0x00800000)               /* subnormal number */
+          {SET_FLOAT_WORD(t,0x4b800000); /* set t= 2**24 */
+           t*=x; GET_FLOAT_WORD(high,t); SET_FLOAT_WORD(t,high/3+B2);
+          }
+        else
+          SET_FLOAT_WORD(t,hx/3+B1);
+
+
+    /* new cbrt to 23 bits */
+        r=t*t/x;
+        s=C+r*t;
+        t*=G+F/(s+E+D/s);
+
+    /* retore the sign bit */
+        GET_FLOAT_WORD(high,t);
+        SET_FLOAT_WORD(t,high|sign);
+        return(t);
+}