[jira] Created: (MATH-322) during ODE integration, the last event in a pair of very close event may not be detected

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[jira] Created: (MATH-322) during ODE integration, the last event in a pair of very close event may not be detected

Gary D. Gregory (Jira)
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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[jira] Resolved: (MATH-322) during ODE integration, the last event in a pair of very close event may not be detected

Gary D. Gregory (Jira)

     [ https://issues.apache.org/jira/browse/MATH-322?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Luc Maisonobe resolved MATH-322.
--------------------------------

    Resolution: Fixed

fixed in subversion repository as of r887794

> during ODE integration, the last event in a pair of very close event may not be detected
> ----------------------------------------------------------------------------------------
>
>                 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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[jira] Closed: (MATH-322) during ODE integration, the last event in a pair of very close event may not be detected

Gary D. Gregory (Jira)
In reply to this post by Gary D. Gregory (Jira)

     [ https://issues.apache.org/jira/browse/MATH-322?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Phil Steitz closed MATH-322.
----------------------------


> during ODE integration, the last event in a pair of very close event may not be detected
> ----------------------------------------------------------------------------------------
>
>                 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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