diff options
Diffstat (limited to 'src/math/jnf.c')
| -rw-r--r-- | src/math/jnf.c | 32 |
1 files changed, 13 insertions, 19 deletions
diff --git a/src/math/jnf.c b/src/math/jnf.c index b0b36e6b..fd291103 100644 --- a/src/math/jnf.c +++ b/src/math/jnf.c @@ -16,12 +16,6 @@ #define _GNU_SOURCE #include "libm.h" -static const float -two = 2.0000000000e+00, /* 0x40000000 */ -one = 1.0000000000e+00; /* 0x3F800000 */ - -static const float zero = 0.0000000000e+00; - float jnf(int n, float x) { int32_t i,hx,ix, sgn; @@ -47,7 +41,7 @@ float jnf(int n, float x) sgn = (n&1)&(hx>>31); /* even n -- 0, odd n -- sign(x) */ x = fabsf(x); if (ix == 0 || ix >= 0x7f800000) /* if x is 0 or inf */ - b = zero; + b = 0.0f; else if((float)n <= x) { /* Safe to use J(n+1,x)=2n/x *J(n,x)-J(n-1,x) */ a = j0f(x); @@ -63,11 +57,11 @@ float jnf(int n, float x) * J(n,x) = 1/n!*(x/2)^n - ... */ if (n > 33) /* underflow */ - b = zero; + b = 0.0f; else { temp = 0.5f * x; b = temp; - for (a=one,i=2; i<=n; i++) { + for (a=1.0f,i=2; i<=n; i++) { a *= (float)i; /* a = n! */ b *= temp; /* b = (x/2)^n */ } @@ -121,10 +115,10 @@ float jnf(int n, float x) q1 = tmp; } m = n+n; - for (t=zero, i = 2*(n+k); i>=m; i -= 2) - t = one/(i/x-t); + for (t=0.0f, i = 2*(n+k); i>=m; i -= 2) + t = 1.0f/(i/x-t); a = t; - b = one; + b = 1.0f; /* estimate log((2/x)^n*n!) = n*log(2/x)+n*ln(n) * Hence, if n*(log(2n/x)) > ... * single 8.8722839355e+01 @@ -134,7 +128,7 @@ float jnf(int n, float x) * likely underflow to zero */ tmp = n; - v = two/x; + v = 2.0f/x; tmp = tmp*logf(fabsf(v*tmp)); if (tmp < 88.721679688f) { for (i=n-1,di=(float)(i+i); i>0; i--) { @@ -142,7 +136,7 @@ float jnf(int n, float x) b *= di; b = b/x - a; a = temp; - di -= two; + di -= 2.0f; } } else { for (i=n-1,di=(float)(i+i); i>0; i--){ @@ -150,12 +144,12 @@ float jnf(int n, float x) b *= di; b = b/x - a; a = temp; - di -= two; + di -= 2.0f; /* scale b to avoid spurious overflow */ if (b > 1e10f) { a /= b; t /= b; - b = one; + b = 1.0f; } } } @@ -183,9 +177,9 @@ float ynf(int n, float x) if (ix > 0x7f800000) return x+x; if (ix == 0) - return -one/zero; + return -1.0f/0.0f; if (hx < 0) - return zero/zero; + return 0.0f/0.0f; sign = 1; if (n < 0) { n = -n; @@ -196,7 +190,7 @@ float ynf(int n, float x) if (n == 1) return sign*y1f(x); if (ix == 0x7f800000) - return zero; + return 0.0f; a = y0f(x); b = y1f(x); |