Merge pull request #692 from oscardssmith/reduce-instability-sensitivity

only bail out as instable when dt is small or error is somewhat conrtolled

src/integrator_interface.jl

@@ -619,10 +619,15 @@ function check_error(integrator::DEIntegrator)
  end
  if integrator.opts.unstable_check(integrator.dt, integrator.u, integrator.p,
  integrator.t)
- if integrator.opts.verbose
- @warn("Instability detected. Aborting")
+ bigtol = max(integrator.opts.reltol, integrator.opts.abstol)
+ # only declare instability if the dt is very small
+ # or we have at least one digit of accuracy in the solution
+ if integrator.dt<eps(integrator.t) || isdefined(integrator, :EEst) && integrator.EEst * bigtol < .1
+ if integrator.opts.verbose
+ @warn("Instability detected. Aborting")
+ end
+ return ReturnCode.Unstable
  end
- return ReturnCode.Unstable
  end
  if last_step_failed(integrator)
  if integrator.opts.verbose