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aherbert pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/commons-numbers.git
The following commit(s) were added to refs/heads/master by this push:
new c0ddd1f Refactor uses of getExponent to internal getMaxExponent(a, b)
method.
c0ddd1f is described below
commit c0ddd1f6094352823007ecf5e33b1ea97545b3ef
Author: aherbert <[email protected]>
AuthorDate: Thu Dec 12 14:22:55 2019 +0000
Refactor uses of getExponent to internal getMaxExponent(a, b) method.
---
.../apache/commons/numbers/complex/Complex.java | 35 +++++++++++++++++-----
1 file changed, 28 insertions(+), 7 deletions(-)
diff --git
a/commons-numbers-complex/src/main/java/org/apache/commons/numbers/complex/Complex.java
b/commons-numbers-complex/src/main/java/org/apache/commons/numbers/complex/Complex.java
index 1b21339..2bd8b1d 100644
---
a/commons-numbers-complex/src/main/java/org/apache/commons/numbers/complex/Complex.java
+++
b/commons-numbers-complex/src/main/java/org/apache/commons/numbers/complex/Complex.java
@@ -491,8 +491,7 @@ public final class Complex implements Serializable {
double d = im2;
int ilogbw = 0;
// Get the exponent to scale the divisor.
- // This is equivalent to (int) Math.log2(double).
- final int exponent = Math.getExponent(Math.max(Math.abs(c),
Math.abs(d)));
+ final int exponent = getMaxExponent(c, d);
if (exponent <= Double.MAX_EXPONENT) {
ilogbw = exponent;
c = Math.scalb(c, -ilogbw);
@@ -1672,8 +1671,7 @@ public final class Complex implements Serializable {
// ln(abs) = ln(abs / scale) + ln(scale)
// Use precise scaling with:
// scale ~ 2^exponent
- final double scale = Math.max(Math.abs(real), Math.abs(imaginary));
- final int exponent = Math.getExponent(scale);
+ final int exponent = getMaxExponent(real, imaginary);
// Implement scaling using 2^-exponent
final double absOs = Math.hypot(Math.scalb(real, -exponent),
Math.scalb(imaginary, -exponent));
// log(2^exponent) = ln2(2^exponent) * log(2)
@@ -1909,9 +1907,8 @@ public final class Complex implements Serializable {
// The alternative of returning infinity for a finite
input is worse.
// Use precise scaling with:
// scale ~ 2^exponent
- final double scale = Math.max(absA, Math.abs(imaginary));
- // Make this even for fast rescaling using
sqrt(2^exponent).
- final int exponent = Math.getExponent(scale) &
MASK_INT_TO_EVEN;
+ // Make exponent even for fast rescaling using
sqrt(2^exponent).
+ final int exponent = getMaxExponent(absA, imaginary) &
MASK_INT_TO_EVEN;
// Implement scaling using 2^-exponent
final double scaleA = Math.scalb(absA, -exponent);
final double scaleB = Math.scalb(imaginary, -exponent);
@@ -2231,6 +2228,30 @@ public final class Complex implements Serializable {
}
/**
+ * Returns the largest unbiased exponent used in the representation of the
+ * two numbers. Special cases:
+ *
+ * <ul>
+ * <li>If either argument is NaN or infinite, then the result is
+ * {@link Double#MAX_EXPONENT} + 1.
+ * <li>If both arguments are zero or subnormal, then the result is
+ * {@link Double#MIN_EXPONENT} -1.
+ * </ul>
+ *
+ * @param a the first value
+ * @param b the second value
+ * @return the maximum unbiased exponent of the values
+ * @see Math#getExponent(double)
+ */
+ private static int getMaxExponent(double a, double b) {
+ // This could return:
+ // Math.getExponent(Math.max(Math.abs(a), Math.abs(b)))
+ // A speed test is required to determine performance.
+
+ return Math.max(Math.getExponent(a), Math.getExponent(b));
+ }
+
+ /**
* Creates an exception.
*
* @param message Message prefix.
