Sébastien Brisard created MATH-812:
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Summary: In RealVector, dotProduct and outerProduct return wrong
results due to misuse of sparse iterators
Key: MATH-812
URL: https://issues.apache.org/jira/browse/MATH-812
Project: Commons Math
Issue Type: Bug
Affects Versions: 3.0
Reporter: Sébastien Brisard
Assignee: Sébastien Brisard
Fix For: 3.1
In class {{RealVector}}, the default implementation of {{RealMatrix
outerProduct(RealVector)}} uses sparse iterators on the entries of the two
vectors. The rationale behind this is that {{0d * x == 0d}} is {{true}} for all
{{double x}}. This assumption is in fact false, since {{0d * NaN == NaN}}.
Proposed fix is to loop through *all* entries of both vectors. This can have a
significant impact on the CPU cost, but robustness should probably be preferred
over speed in default implementations.
Same issue occurs with {{double dotProduct(RealVector)}}, which uses sparse
iterators for {{this}} only.
Another option would be to through an exception if {{isNaN()}} is {{true}}, in
which case caching could be used for both {{isNaN()}} and {{isInfinite()}}.
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