diff options
Diffstat (limited to 'src/pkg/math/log.go')
| -rw-r--r-- | src/pkg/math/log.go | 29 |
1 files changed, 14 insertions, 15 deletions
diff --git a/src/pkg/math/log.go b/src/pkg/math/log.go index 4f9a37606..22df7ac1b 100644 --- a/src/pkg/math/log.go +++ b/src/pkg/math/log.go @@ -43,7 +43,7 @@ package math // | | // Note that 2s = f - s*f = f - hfsq + s*hfsq, where hfsq = f*f/2. // In order to guarantee error in log below 1ulp, we compute log by -// log(1+f) = f - s*(f - R) (if f is not too large) +// log(1+f) = f - s*(f - R) (if f is not too large) // log(1+f) = f - (hfsq - s*(hfsq+R)). (better accuracy) // // 3. Finally, log(x) = k*Ln2 + log(1+f). @@ -76,15 +76,15 @@ package math // Log(NaN) = NaN func Log(x float64) float64 { const ( - Ln2Hi = 6.93147180369123816490e-01; /* 3fe62e42 fee00000 */ - Ln2Lo = 1.90821492927058770002e-10; /* 3dea39ef 35793c76 */ - L1 = 6.666666666666735130e-01; /* 3FE55555 55555593 */ - L2 = 3.999999999940941908e-01; /* 3FD99999 9997FA04 */ - L3 = 2.857142874366239149e-01; /* 3FD24924 94229359 */ - L4 = 2.222219843214978396e-01; /* 3FCC71C5 1D8E78AF */ - L5 = 1.818357216161805012e-01; /* 3FC74664 96CB03DE */ - L6 = 1.531383769920937332e-01; /* 3FC39A09 D078C69F */ - L7 = 1.479819860511658591e-01; /* 3FC2F112 DF3E5244 */ + Ln2Hi = 6.93147180369123816490e-01; /* 3fe62e42 fee00000 */ + Ln2Lo = 1.90821492927058770002e-10; /* 3dea39ef 35793c76 */ + L1 = 6.666666666666735130e-01; /* 3FE55555 55555593 */ + L2 = 3.999999999940941908e-01; /* 3FD99999 9997FA04 */ + L3 = 2.857142874366239149e-01; /* 3FD24924 94229359 */ + L4 = 2.222219843214978396e-01; /* 3FCC71C5 1D8E78AF */ + L5 = 1.818357216161805012e-01; /* 3FC74664 96CB03DE */ + L6 = 1.531383769920937332e-01; /* 3FC39A09 D078C69F */ + L7 = 1.479819860511658591e-01; /* 3FC2F112 DF3E5244 */ ) // special cases @@ -103,7 +103,7 @@ func Log(x float64) float64 { f1 *= 2; ki--; } - f := f1 - 1; + f := f1-1; k := float64(ki); // compute @@ -112,9 +112,9 @@ func Log(x float64) float64 { s4 := s2*s2; t1 := s2*(L1 + s4*(L3 + s4*(L5 + s4*L7))); t2 := s4*(L2 + s4*(L4 + s4*L6)); - R := t1 + t2; + R := t1+t2; hfsq := 0.5*f*f; - return k*Ln2Hi - ((hfsq-(s*(hfsq+R)+k*Ln2Lo)) - f); + return k*Ln2Hi - ((hfsq-(s*(hfsq+R) + k*Ln2Lo))-f); } // Log10 returns the decimal logarithm of x. @@ -123,6 +123,5 @@ func Log10(x float64) float64 { if x <= 0 { return NaN(); } - return Log(x) * (1/Ln10); + return Log(x)*(1/Ln10); } - |