Don't call CVode with an interval it cannot integrate - #1621
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## master #1621 +/- ##
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doStepCVODE accumulates end_time while the event times come from the FMU, so an event landing on the last ULP before end_time leaves time < end_time true with nothing integrable in between: time = 0.080000000000000001665 clock tick reported by the FMU end_time = 0.080000000000000015543 accumulated by the loop tout = min(tnext, end_time) = end_time gap = 1.39e-17 CVode rejects such an interval with CV_TOO_CLOSE, but only on the first call after a re-init - which is exactly the call following every event - so the whole simulation fails there. Skip the call and take end_time as reached, using CVode's own too-close test. Reproduced by simulation/clockedStepBoundary: a Modelica.Clocked FMU whose tick times are exact (k * period) against a communication step of 0.008, which fails at t = 0.08 without this change. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
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Related Issues
Related to #1600. In OpenModelica/OpenModelica#16158 we get a new error with OMSimulator.
Purpose
doStepCVODE accumulates end_time while the event times come from the FMU, so an event landing on the last ULP before end_time leaves time < end_time true with nothing integrable in between:
time = 0.080000000000000001665 clock tick reported by the FMU
end_time = 0.080000000000000015543 accumulated by the loop
tout = min(tnext, end_time) = end_time gap = 1.39e-17
CVode rejects such an interval with CV_TOO_CLOSE, but only on the first call after a re-init - which is exactly the call following every event - so the whole simulation fails there.
Approach
Skip the call and take end_time as reached, using CVode's own too-close test.