during ODE integration, the last event in a pair of very close event may not be
detected
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Key: MATH-322
URL: https://issues.apache.org/jira/browse/MATH-322
Project: Commons Math
Issue Type: Bug
Affects Versions: 2.0
Environment: All
Reporter: Luc Maisonobe
Assignee: Luc Maisonobe
Fix For: 2.1
When an events follows a previous one very closely, it may be ignored. The
occurrence of the bug depends on the side of the bracketing interval that was
selected. For example consider a switching function that is increasing around
first event around t = 90, reaches its maximum and is decreasing around the
second event around t = 135. If an integration step spans from 67.5 and 112.5,
the switching function values at start and end of step will have opposite
signs, so the first event will be detected. The solver will find the event
really occurs at 90.0 and will therefore truncate the step at 90.0. The next
step will start from where the first step ends, i.e. it will start at 90.0.
Let's say this step spans from 90.0 to 153.0. The switching function switches
once again in this step.
If the solver for the first event converged to a value slightly before 90.0
(say 89.9999999), then the switch will not be detected because g(89.9999999)
and g(153.0) are both negative.
This bug was introduced as of r781157 (2009-06-02) when special handling of
events very close to step start was added.
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