From 0b44a0315b47dd8eced9f3b7f31580cf14bbfc01 Mon Sep 17 00:00:00 2001
From: Rich Felker <dalias@aerifal.cx>
Date: Sat, 12 Feb 2011 00:22:29 -0500
Subject: initial check-in, version 0.5.0

---
 src/math/e_logf.c | 81 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 81 insertions(+)
 create mode 100644 src/math/e_logf.c

(limited to 'src/math/e_logf.c')

diff --git a/src/math/e_logf.c b/src/math/e_logf.c
new file mode 100644
index 00000000..46a8b8ce
--- /dev/null
+++ b/src/math/e_logf.c
@@ -0,0 +1,81 @@
+/* e_logf.c -- float version of e_log.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"
+
+static const float
+ln2_hi =   6.9313812256e-01,    /* 0x3f317180 */
+ln2_lo =   9.0580006145e-06,    /* 0x3717f7d1 */
+two25 =    3.355443200e+07,     /* 0x4c000000 */
+Lg1 = 6.6666668653e-01, /* 3F2AAAAB */
+Lg2 = 4.0000000596e-01, /* 3ECCCCCD */
+Lg3 = 2.8571429849e-01, /* 3E924925 */
+Lg4 = 2.2222198546e-01, /* 3E638E29 */
+Lg5 = 1.8183572590e-01, /* 3E3A3325 */
+Lg6 = 1.5313838422e-01, /* 3E1CD04F */
+Lg7 = 1.4798198640e-01; /* 3E178897 */
+
+static const float zero   =  0.0;
+
+float
+logf(float x)
+{
+        float hfsq,f,s,z,R,w,t1,t2,dk;
+        int32_t k,ix,i,j;
+
+        GET_FLOAT_WORD(ix,x);
+
+        k=0;
+        if (ix < 0x00800000) {                  /* x < 2**-126  */
+            if ((ix&0x7fffffff)==0)
+                return -two25/zero;             /* log(+-0)=-inf */
+            if (ix<0) return (x-x)/zero;        /* log(-#) = NaN */
+            k -= 25; x *= two25; /* subnormal number, scale up x */
+            GET_FLOAT_WORD(ix,x);
+        }
+        if (ix >= 0x7f800000) return x+x;
+        k += (ix>>23)-127;
+        ix &= 0x007fffff;
+        i = (ix+(0x95f64<<3))&0x800000;
+        SET_FLOAT_WORD(x,ix|(i^0x3f800000));    /* normalize x or x/2 */
+        k += (i>>23);
+        f = x-(float)1.0;
+        if((0x007fffff&(15+ix))<16) {   /* |f| < 2**-20 */
+            if(f==zero) { if(k==0) return zero;  else {dk=(float)k;
+                                 return dk*ln2_hi+dk*ln2_lo;} }
+            R = f*f*((float)0.5-(float)0.33333333333333333*f);
+            if(k==0) return f-R; else {dk=(float)k;
+                     return dk*ln2_hi-((R-dk*ln2_lo)-f);}
+        }
+        s = f/((float)2.0+f);
+        dk = (float)k;
+        z = s*s;
+        i = ix-(0x6147a<<3);
+        w = z*z;
+        j = (0x6b851<<3)-ix;
+        t1= w*(Lg2+w*(Lg4+w*Lg6));
+        t2= z*(Lg1+w*(Lg3+w*(Lg5+w*Lg7)));
+        i |= j;
+        R = t2+t1;
+        if(i>0) {
+            hfsq=(float)0.5*f*f;
+            if(k==0) return f-(hfsq-s*(hfsq+R)); else
+                     return dk*ln2_hi-((hfsq-(s*(hfsq+R)+dk*ln2_lo))-f);
+        } else {
+            if(k==0) return f-s*(f-R); else
+                     return dk*ln2_hi-((s*(f-R)-dk*ln2_lo)-f);
+        }
+}
-- 
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