FastMath scalb() does not handle large magnitude exponents correctly
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Key: MATH-502
URL: https://issues.apache.org/jira/browse/MATH-502
Project: Commons Math
Issue Type: Bug
Affects Versions: 2.2, 3.0
Reporter: Sebb
Fix For: 2.2, 3.0
scalb does not handle MAX_VALUE exponents properly:
double scalb(-1.7976931348623157E308, 2147483647) expected -Infinity actual
-8.988465674311579E307 entries [6, 5]
double scalb(1.7976931348623157E308, 2147483647) expected Infinity actual
8.988465674311579E307 entries [7, 5]
double scalb(-1.1102230246251565E-16, 2147483647) expected -Infinity actual
-5.551115123125783E-17 entries [8, 5]
double scalb(1.1102230246251565E-16, 2147483647) expected Infinity actual
5.551115123125783E-17 entries [9, 5]
double scalb(-2.2250738585072014E-308, 2147483647) expected -Infinity actual
-0.0 entries [10, 5]
double scalb(2.2250738585072014E-308, 2147483647) expected Infinity actual 0.0
entries [11, 5]
float scalb(3.4028235E38, 2147483647) expected Infinity actual 1.7014117E38
entries [7, 5]
float scalb(-3.4028235E38, 2147483647) expected -Infinity actual -1.7014117E38
entries [9, 5]
It looks as though the problem is with the calculation of the scaledExponent -
for large values, this can wrap round, so some of the checks against its value
may give misleading results.
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