Repository: commons-math Updated Branches: refs/heads/master 75efbfd6b -> 3d9a76877
MATH-1198 Simplify FastMath exp function Hopefully also fix Java 1.5 JIT bug Project: http://git-wip-us.apache.org/repos/asf/commons-math/repo Commit: http://git-wip-us.apache.org/repos/asf/commons-math/commit/f7e42d2c Tree: http://git-wip-us.apache.org/repos/asf/commons-math/tree/f7e42d2c Diff: http://git-wip-us.apache.org/repos/asf/commons-math/diff/f7e42d2c Branch: refs/heads/master Commit: f7e42d2ccf949a5893a439227c8c6bafd2598f26 Parents: 6383def Author: Sebb <s...@apache.org> Authored: Sun Jan 25 00:26:21 2015 +0000 Committer: Sebb <s...@apache.org> Committed: Sun Jan 25 00:26:21 2015 +0000 ---------------------------------------------------------------------- .../org/apache/commons/math3/util/FastMath.java | 28 +++++++------------- 1 file changed, 10 insertions(+), 18 deletions(-) ---------------------------------------------------------------------- http://git-wip-us.apache.org/repos/asf/commons-math/blob/f7e42d2c/src/main/java/org/apache/commons/math3/util/FastMath.java ---------------------------------------------------------------------- diff --git a/src/main/java/org/apache/commons/math3/util/FastMath.java b/src/main/java/org/apache/commons/math3/util/FastMath.java index 09c5976..2ed0909 100644 --- a/src/main/java/org/apache/commons/math3/util/FastMath.java +++ b/src/main/java/org/apache/commons/math3/util/FastMath.java @@ -867,20 +867,17 @@ public class FastMath { private static double exp(double x, double extra, double[] hiPrec) { double intPartA; double intPartB; - int intVal; + int intVal = (int) x; /* Lookup exp(floor(x)). * intPartA will have the upper 22 bits, intPartB will have the lower * 52 bits. */ if (x < 0.0) { - intVal = (int) -x; - // TEMP: special handling of negative_infinity - // the above might fail in non-reproducible ways with Sun JDK 1.5, - // most likely due to a bug in the JIT. Add a safe-guard for very - // negative numbers. - if (intVal > 746 || x < Integer.MIN_VALUE) { + // We don't check against intVal here as conversion of large negative double values + // may be affected by a JIT bug. Subsequent comparisons can safely use intVal + if (x < -746d) { if (hiPrec != null) { hiPrec[0] = 0.0; hiPrec[1] = 0.0; @@ -888,7 +885,7 @@ public class FastMath { return 0.0; } - if (intVal > 709) { + if (intVal < -709) { /* This will produce a subnormal output */ final double result = exp(x+40.19140625, extra, hiPrec) / 285040095144011776.0; if (hiPrec != null) { @@ -898,7 +895,7 @@ public class FastMath { return result; } - if (intVal == 709) { + if (intVal == -709) { /* exp(1.494140625) is nearly a machine number... */ final double result = exp(x+1.494140625, extra, hiPrec) / 4.455505956692756620; if (hiPrec != null) { @@ -908,15 +905,9 @@ public class FastMath { return result; } - intVal++; - - intPartA = ExpIntTable.EXP_INT_TABLE_A[EXP_INT_TABLE_MAX_INDEX-intVal]; - intPartB = ExpIntTable.EXP_INT_TABLE_B[EXP_INT_TABLE_MAX_INDEX-intVal]; + intVal--; - intVal = -intVal; } else { - intVal = (int) x; - if (intVal > 709) { if (hiPrec != null) { hiPrec[0] = Double.POSITIVE_INFINITY; @@ -925,10 +916,11 @@ public class FastMath { return Double.POSITIVE_INFINITY; } - intPartA = ExpIntTable.EXP_INT_TABLE_A[EXP_INT_TABLE_MAX_INDEX+intVal]; - intPartB = ExpIntTable.EXP_INT_TABLE_B[EXP_INT_TABLE_MAX_INDEX+intVal]; } + intPartA = ExpIntTable.EXP_INT_TABLE_A[EXP_INT_TABLE_MAX_INDEX+intVal]; + intPartB = ExpIntTable.EXP_INT_TABLE_B[EXP_INT_TABLE_MAX_INDEX+intVal]; + /* Get the fractional part of x, find the greatest multiple of 2^-10 less than * x and look up the exp function of it. * fracPartA will have the upper 22 bits, fracPartB the lower 52 bits.
