diff options
Diffstat (limited to 'src/pkg/math/exp.go')
| -rw-r--r-- | src/pkg/math/exp.go | 38 |
1 files changed, 19 insertions, 19 deletions
diff --git a/src/pkg/math/exp.go b/src/pkg/math/exp.go index cdee0d70a..9ad2b3877 100644 --- a/src/pkg/math/exp.go +++ b/src/pkg/math/exp.go @@ -90,18 +90,18 @@ package math // Very small values underflow to 1. func Exp(x float64) float64 { const ( - Ln2Hi = 6.93147180369123816490e-01; - Ln2Lo = 1.90821492927058770002e-10; - Log2e = 1.44269504088896338700e+00; - P1 = 1.66666666666666019037e-01; /* 0x3FC55555; 0x5555553E */ - P2 = -2.77777777770155933842e-03; /* 0xBF66C16C; 0x16BEBD93 */ - P3 = 6.61375632143793436117e-05; /* 0x3F11566A; 0xAF25DE2C */ - P4 = -1.65339022054652515390e-06; /* 0xBEBBBD41; 0xC5D26BF1 */ - P5 = 4.13813679705723846039e-08; /* 0x3E663769; 0x72BEA4D0 */ + Ln2Hi = 6.93147180369123816490e-01 + Ln2Lo = 1.90821492927058770002e-10 + Log2e = 1.44269504088896338700e+00 + P1 = 1.66666666666666019037e-01 /* 0x3FC55555; 0x5555553E */ + P2 = -2.77777777770155933842e-03 /* 0xBF66C16C; 0x16BEBD93 */ + P3 = 6.61375632143793436117e-05 /* 0x3F11566A; 0xAF25DE2C */ + P4 = -1.65339022054652515390e-06 /* 0xBEBBBD41; 0xC5D26BF1 */ + P5 = 4.13813679705723846039e-08 /* 0x3E663769; 0x72BEA4D0 */ - Overflow = 7.09782712893383973096e+02; - Underflow = -7.45133219101941108420e+02; - NearZero = 1.0 / (1 << 28); // 2^-28 + Overflow = 7.09782712893383973096e+02 + Underflow = -7.45133219101941108420e+02 + NearZero = 1.0 / (1 << 28) // 2^-28 ) // special cases @@ -119,21 +119,21 @@ func Exp(x float64) float64 { } // reduce; computed as r = hi - lo for extra precision. - var k int; + var k int switch { case x < 0: k = int(Log2e*x - 0.5) case x > 0: k = int(Log2e*x + 0.5) } - hi := x - float64(k)*Ln2Hi; - lo := float64(k) * Ln2Lo; - r := hi - lo; + hi := x - float64(k)*Ln2Hi + lo := float64(k) * Ln2Lo + r := hi - lo // compute - t := r * r; - c := r - t*(P1+t*(P2+t*(P3+t*(P4+t*P5)))); - y := 1 - ((lo - (r*c)/(2-c)) - hi); + t := r * r + c := r - t*(P1+t*(P2+t*(P3+t*(P4+t*P5)))) + y := 1 - ((lo - (r*c)/(2-c)) - hi) // TODO(rsc): make sure Ldexp can handle boundary k - return Ldexp(y, k); + return Ldexp(y, k) } |