add mintimestep option

raster/r.sim/r.sim.water/main.c

@@ -239,6 +239,18 @@ int main(int argc, char *argv[])
     parm.niter->description = _("Time used for iterations [minutes]");
     parm.niter->guisection = _("Parameters");
 
+    parm.mintimestep = G_define_option();
+    parm.mintimestep->key = "mintimestep";
+    parm.mintimestep->type = TYPE_DOUBLE;
+    parm.mintimestep->answer = "0.0";
+    parm.mintimestep->required = NO;
+    parm.mintimestep->label =
+        _("Minimum tine step for the simulation [seconds]");
+    parm.mintimestep->description =
+        _("A larger minimum tine step substancially reduces processing time, "
+          "but at the cost of accuracy");
+    parm.mintimestep->guisection = _("Parameters");
+
     parm.outiter = G_define_option();
     parm.outiter->key = "output_step";
     parm.outiter->type = TYPE_INTEGER;
@@ -319,8 +331,9 @@ int main(int argc, char *argv[])
     parm.threads->type = TYPE_INTEGER;
     parm.threads->answer = NUM_THREADS;
     parm.threads->required = NO;
-    parm.threads->description =
-        _("Number of threads which will be used for parallel compute");
+    parm.threads->description = _(
+        "Number of threads which will be used for parallel compute. Increasing "
+        "the number of threads does not really speed up the simulation.");
     parm.threads->guisection = _("Parameters");
 
     if (G_parser(argc, argv))
@@ -388,6 +401,7 @@ int main(int argc, char *argv[])
     G_debug(3, "Parsing numeric parameters");
 
     sscanf(parm.niter->answer, "%d", &wp.timesec);
+    sscanf(parm.mintimestep->answer, "%lf", &wp.mintimestep);
     sscanf(parm.outiter->answer, "%d", &wp.iterout);
     sscanf(parm.diffc->answer, "%lf", &wp.frac);
     sscanf(parm.hmax->answer, "%lf", &wp.hhmax);

raster/r.sim/simlib/hydro.c

@@ -104,6 +104,7 @@ int iterout, mx2o, my2o;
 int miter, nwalka;
 double timec;
 int ts, timesec;
+double mintimestep;
 
 double rain_val;
 double manin_val;

raster/r.sim/simlib/input.c

@@ -95,6 +95,7 @@ void WaterParams_init(struct WaterParams *wp)
     wp->timec = 0;
     wp->ts = 0;
     wp->timesec = 0;
+    wp->mintimestep = 0;
 
     wp->rain_val = 0;
     wp->manin_val = 0;
@@ -201,6 +202,7 @@ void init_library_globals(struct WaterParams *wp)
     timec = wp->timec;
     ts = wp->ts;
     timesec = wp->timesec;
+    mintimestep = wp->mintimestep;
 
     rain_val = wp->rain_val;
     manin_val = wp->manin_val;
@@ -508,6 +510,9 @@ int grad_check(void)
         deltaw = 0.8 / (sigmax * vmax);          /*time step for sediment */
     deltap = 0.25 * sqrt(stepx * stepy) / vmean; /*time step for water */
 
+    if (deltap < mintimestep)
+        deltap = mintimestep;
+
     if (deltaw > deltap)
         timec = 4.;
     else

raster/r.sim/simlib/simlib.h

@@ -35,6 +35,7 @@ struct WaterParams {
     int miter, nwalka;
     double timec;
     int ts, timesec;
+    double mintimestep;
 
     double rain_val;
     double manin_val;
@@ -86,10 +87,10 @@ void free_walkers(void);
 
 struct options {
     struct Option *elevin, *dxin, *dyin, *rain, *infil, *traps, *manin,
-        *observation, *depth, *disch, *err, *outwalk, *nwalk, *niter, *outiter,
-        *density, *diffc, *hmax, *halpha, *hbeta, *wdepth, *detin, *tranin,
-        *tauin, *tc, *et, *conc, *flux, *erdep, *rainval, *maninval, *infilval,
-        *logfile, *seed, *threads;
+        *observation, *depth, *disch, *err, *outwalk, *nwalk, *niter,
+        *mintimestep, *outiter, *density, *diffc, *hmax, *halpha, *hbeta,
+        *wdepth, *detin, *tranin, *tauin, *tc, *et, *conc, *flux, *erdep,
+        *rainval, *maninval, *infilval, *logfile, *seed, *threads;
 };
 
 struct flags {

raster/r.sim/simlib/waterglobs.h

@@ -111,6 +111,7 @@ extern int iterout, mx2o, my2o;
 extern int miter, nwalka;
 extern double timec;
 extern int ts, timesec;
+extern double mintimestep;
 
 extern double rain_val;
 extern double manin_val;