Sébastien Brisard created MATH-803:
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Summary: Bugs in OpenMapRealVector.ebeMultiply(RealVector) and
ebeDivide(RealVector)
Key: MATH-803
URL: https://issues.apache.org/jira/browse/MATH-803
Project: Commons Math
Issue Type: Bug
Affects Versions: 3.0
Reporter: Sébastien Brisard
Assignee: Sébastien Brisard
{{OpenMapRealVector.ebeMultiply(RealVector)}} and
{{OpenMapRealVector.ebeDivide(RealVector)}} return wrong values when one entry
of the specified {{RealVector}} is nan or infinity. The bug is easy to
understand. Here is the current implementation of {{ebeMultiply}}
{code:java}
public OpenMapRealVector ebeMultiply(RealVector v) {
checkVectorDimensions(v.getDimension());
OpenMapRealVector res = new OpenMapRealVector(this);
Iterator iter = entries.iterator();
while (iter.hasNext()) {
iter.advance();
res.setEntry(iter.key(), iter.value() * v.getEntry(iter.key()));
}
return res;
}
{code}
The assumption is that for any double {{x}}, {{x * 0d == 0d}} holds, which is
not true. The bug is easy enough to identify, but more complex to solve. The
only solution I can come up with is to loop through *all* entries of v (instead
of those entries which correspond to non-zero entries of this). I'm afraid
about performance losses.
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