Revision: 19701
Author: [email protected]
Date: Fri Mar 7 08:42:10 2014 UTC
Log: Harmony: move implementation of Math.log1p and Math.expm1 to
Javascript.
[email protected]
Review URL: https://codereview.chromium.org/179533003
http://code.google.com/p/v8/source/detail?r=19701
Modified:
/branches/bleeding_edge/src/harmony-math.js
/branches/bleeding_edge/src/runtime.cc
/branches/bleeding_edge/src/runtime.h
=======================================
--- /branches/bleeding_edge/src/harmony-math.js Wed Feb 19 13:49:59 2014 UTC
+++ /branches/bleeding_edge/src/harmony-math.js Fri Mar 7 08:42:10 2014 UTC
@@ -174,21 +174,51 @@
}
-//ES6 draft 09-27-13, section 20.2.2.9.
+// ES6 draft 09-27-13, section 20.2.2.9.
function MathCbrt(x) {
return %Math_cbrt(TO_NUMBER_INLINE(x));
}
-//ES6 draft 09-27-13, section 20.2.2.14.
+// ES6 draft 09-27-13, section 20.2.2.14.
+// Use Taylor series to approximate.
+// exp(x) - 1 at 0 == -1 + exp(0) + exp'(0)*x/1! + exp''(0)*x^2/2! + ...
+// == x/1! + x^2/2! + x^3/3! + ...
+// The closer x is to 0, the fewer terms are required.
function MathExpm1(x) {
- return %Math_expm1(TO_NUMBER_INLINE(x));
+ if (!IS_NUMBER(x)) x = NonNumberToNumber(x);
+ var xabs = MathAbs(x);
+ if (xabs < 2E-7) {
+ return x * (1 + x * (1/2));
+ } else if (xabs < 6E-5) {
+ return x * (1 + x * (1/2 + x * (1/6)));
+ } else if (xabs < 2E-2) {
+ return x * (1 + x * (1/2 + x * (1/6 +
+ x * (1/24 + x * (1/120 + x * (1/720))))));
+ } else { // Use regular exp if not close enough to 0.
+ return MathExp(x) - 1;
+ }
}
-//ES6 draft 09-27-13, section 20.2.2.20.
+// ES6 draft 09-27-13, section 20.2.2.20.
+// Use Taylor series to approximate. With y = x + 1;
+// log(y) at 1 == log(1) + log'(1)(y-1)/1! + log''(1)(y-1)^2/2! + ...
+// == 0 + x - x^2/2 + x^3/3 ...
+// The closer x is to 0, the fewer terms are required.
function MathLog1p(x) {
- return %Math_log1p(TO_NUMBER_INLINE(x));
+ if (!IS_NUMBER(x)) x = NonNumberToNumber(x);
+ var xabs = MathAbs(x);
+ if (xabs < 1E-7) {
+ return x * (1 - x * (1/2));
+ } else if (xabs < 3E-5) {
+ return x * (1 - x * (1/2 - x * (1/3)));
+ } else if (xabs < 7E-3) {
+ return x * (1 - x * (1/2 - x * (1/3 - x * (1/4 -
+ x * (1/5 - x * (1/6 - x * (1/7)))))));
+ } else { // Use regular log if not close enough to 0.
+ return MathLog(1 + x);
+ }
}
=======================================
--- /branches/bleeding_edge/src/runtime.cc Fri Mar 7 08:36:18 2014 UTC
+++ /branches/bleeding_edge/src/runtime.cc Fri Mar 7 08:42:10 2014 UTC
@@ -7692,67 +7692,6 @@
double result = (x > 0) ? CubeRoot(x) : -CubeRoot(-x);
return isolate->heap()->AllocateHeapNumber(result);
}
-
-
-RUNTIME_FUNCTION(MaybeObject*, Runtime_Math_log1p) {
- SealHandleScope shs(isolate);
- ASSERT(args.length() == 1);
- CONVERT_DOUBLE_ARG_CHECKED(x, 0);
-
- double x_abs = std::fabs(x);
- // Use Taylor series to approximate. With y = x + 1;
- // log(y) at 1 == log(1) + log'(1)(y-1)/1! + log''(1)(y-1)^2/2! + ...
- // == 0 + x - x^2/2 + x^3/3 ...
- // The closer x is to 0, the fewer terms are required.
- static const double threshold_2 = 1.0 / 0x00800000;
- static const double threshold_3 = 1.0 / 0x00008000;
- static const double threshold_7 = 1.0 / 0x00000080;
-
- double result;
- if (x_abs < threshold_2) {
- result = x * (1.0/1.0 - x * 1.0/2.0);
- } else if (x_abs < threshold_3) {
- result = x * (1.0/1.0 - x * (1.0/2.0 - x * (1.0/3.0)));
- } else if (x_abs < threshold_7) {
- result = x * (1.0/1.0 - x * (1.0/2.0 - x * (
- 1.0/3.0 - x * (1.0/4.0 - x * (
- 1.0/5.0 - x * (1.0/6.0 - x * (
- 1.0/7.0)))))));
- } else { // Use regular log if not close enough to 0.
- result = std::log(1.0 + x);
- }
- return isolate->heap()->AllocateHeapNumber(result);
-}
-
-
-RUNTIME_FUNCTION(MaybeObject*, Runtime_Math_expm1) {
- SealHandleScope shs(isolate);
- ASSERT(args.length() == 1);
- CONVERT_DOUBLE_ARG_CHECKED(x, 0);
-
- double x_abs = std::fabs(x);
- // Use Taylor series to approximate.
- // exp(x) - 1 at 0 == -1 + exp(0) + exp'(0)*x/1! + exp''(0)*x^2/2! + ...
- // == x/1! + x^2/2! + x^3/3! + ...
- // The closer x is to 0, the fewer terms are required.
- static const double threshold_2 = 1.0 / 0x00400000;
- static const double threshold_3 = 1.0 / 0x00004000;
- static const double threshold_6 = 1.0 / 0x00000040;
-
- double result;
- if (x_abs < threshold_2) {
- result = x * (1.0/1.0 + x * (1.0/2.0));
- } else if (x_abs < threshold_3) {
- result = x * (1.0/1.0 + x * (1.0/2.0 + x * (1.0/6.0)));
- } else if (x_abs < threshold_6) {
- result = x * (1.0/1.0 + x * (1.0/2.0 + x * (
- 1.0/6.0 + x * (1.0/24.0 + x * (
- 1.0/120.0 + x * (1.0/720.0))))));
- } else { // Use regular exp if not close enough to 0.
- result = std::exp(x) - 1.0;
- }
- return isolate->heap()->AllocateHeapNumber(result);
-}
static const double kPiDividedBy4 = 0.78539816339744830962;
=======================================
--- /branches/bleeding_edge/src/runtime.h Tue Mar 4 12:43:05 2014 UTC
+++ /branches/bleeding_edge/src/runtime.h Fri Mar 7 08:42:10 2014 UTC
@@ -179,8 +179,6 @@
F(Math_atan, 1, 1) \
F(Math_log, 1, 1) \
F(Math_cbrt, 1, 1) \
- F(Math_log1p, 1, 1) \
- F(Math_expm1, 1, 1) \
F(Math_sqrt, 1, 1) \
F(Math_exp, 1, 1) \
F(Math_floor, 1, 1) \
--
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