Add minimum timestep to simulator config (#120)

Author: strene

src/simulator/config.jl

@@ -15,6 +15,7 @@ Negative values disable output. The interpretation of this number is subject to
     # Convergence tests
     add_option!(cfg, :max_timestep_cuts, 5, "Max time step cuts in a single mini step before termination of simulation.", types = Int, values = 0:10000)
     add_option!(cfg, :max_timestep, Inf, "Max time step length.", types = Float64)
+    add_option!(cfg, :min_timestep, 0.0, "Min time step length.", types = Float64)
     add_option!(cfg, :max_nonlinear_iterations, 15, "Max number of nonlinear iterations in a Newton solve before time-step is cut.", types = Int, values = 0:10000)
     add_option!(cfg, :min_nonlinear_iterations, 1, "Minimum number of nonlinear iterations in Newton solver.", description = "This number of Newtion iterations is always performed, even if all equations are converged.", types = Int, values = 0:10000)
     add_option!(cfg, :failure_cuts_timestep, false, "Cut the timestep if exceptions occur during step. If set to false, throw errors and terminate.", types = Bool)

src/simulator/timesteps.jl

@@ -29,7 +29,7 @@ function pick_timestep(sim, config, dt_prev, dT, forces, reports, current_report
     if dt > half_remain && dt < remaining_time
         dt = half_remain
     end
-    dt = min(dt, config[:max_timestep])
+    dt = clamp(dt, config[:min_timestep], config[:max_timestep])
     if config[:info_level] > 1
         ratio = dt/dt_prev
         if ratio > 5
@@ -49,6 +49,9 @@ function pick_timestep(sim, config, dt_prev, dT, forces, reports, current_report
 end
 
 function cut_timestep(sim, config, dt, dT, forces, reports; step_index = NaN, cut_count = 0)
+    if isapprox(dt, config[:min_timestep])
+        return NaN
+    end
     for sel in config[:timestep_selectors]
         candidate = pick_cut_timestep(sel, sim, config, dt, dT, forces, reports, cut_count)
         dt = min(dt, candidate)