JDK 8 and 9 RFR of 8030212: Several api.java.util.stream tests got "NaN" value instead of "Infinity" or "-Infinity"
joe.darcy at oracle.com
Sun Dec 22 14:54:22 UTC 2013
Testing (eventually) revealed that changing the streams floating point
sum and average algorithms to use compensated summation (JDK-8006572
DoubleStream.sum() & DoubleSummaryStats implementations that reduce
numerical errors), changed the behavior of the code on streams with
infinite values: NaN was returned instead of infinity:
8030212: Several api.java.util.stream tests got "NaN" value instead
of "Infinity" or "-Infinity"
The specification doesn't explicitly state how non-finite values in
streams should be handled (and it should be updated to do so in 9,
JDK-8030942 Explicitly state floating-point summation requirements on
non-finite inputs), but it isn't unreasonable to assume that a properly
signed infinity should result.
Towards that end, I've prepared a webrev that uses an additional simple
sum to distinguish a spurious NaN sum in the result:
This may not be the optimal way to track this situation, additional
logic in the compensated summation code is possible, but if needed the
implementation can be refined in JDK 9 and the 8 updates.
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