Feature update (#118)

* Add a min_dt limit, triggering a clean exit of the code.

* Extend the checkMessage to enable more actions.

* Update doc.

* small docs fix

Co-authored-by: nickwimer <nicholas.wimer@gmail.com>

Docs/source/LMeXControls.rst

@@ -60,6 +60,7 @@ Time stepping parameters
     amr.stop_time     = 0.001              # Maximum simulation time [s]
     amr.cfl           = 0.5                # [OPT, DEF=0.7] CFL for advection-controlled dt estimate
     amr.fixed_dt      = 1e-6               # [OPT] optional fixed dt (override CFL condition)
+    amr.min_dt        = 1e-11              # [OPT, DEF=1e-12] small time step size limit triggering simulation termination
     amr.init_dt       = 1e-6               # [OPT] optional initial dt (override CFL condition upon initialization)
     amr.dt_shrink     = 0.0001             # [OPT, DEF=1.0] dt factor upon initialization
     amr.dt_change_max = 1.1                # [OPT, DEF=1.1] maximum dt change between consecutive steps
@@ -277,3 +278,38 @@ the state variables on a 'x','y' or 'z' aligned plane and writting a 2D plotfile
     peleLM.ynormal.center = 0.0
     peleLM.ynormal.int    = 10
     peleLM.ynormal.interpolation = Quadratic
+
+
+Run-time control
+--------------------
+
+Following some of AMReX's AmrLevel class implementation, PeleLMeX provides a couple of triggers to interact with the code while
+it is running. This can be done by adding an empty file to the folder where the simulation is currently running using for 
+example:
+
+::
+
+    touch plt_and_continue
+
+The list of available triggers is:
+
+.. list-table:: PeleLMeX run-time triggers
+    :widths: 50 100
+    :header-rows: 1
+
+    * - File
+      - Function
+    * - plt_and_continue
+      - Write a pltfile to disk and pursue the simulation
+    * - chk_and_continue
+      - Write a chkfile to disk and pursue the simulation
+    * - dump_and_stop
+      - Write both pltfile and chkfile to disk and stop the simulation
+
+By default, the code checks if these files exist every 10 time steps, but the user can either increase or decrease the 
+frequency using:
+
+::
+
+    amr.message_int      = 20                # [OPT, DEF=10] Frequency for checking the presence of trigger files
+    

Source/PeleLM.H

@@ -524,7 +524,7 @@ class PeleLM : public amrex::AmrCore {
    // I/O
    void WritePlotFile();
    bool writePlotNow();
-   bool checkMessage();
+   bool checkMessage(const std::string &a_action);
    void WriteCheckPointFile();
    void ReadCheckPointFile();
    bool writeCheckNow();
@@ -1105,6 +1105,7 @@ class PeleLM : public amrex::AmrCore {
    amrex::Real m_cfl          = 0.7;
    amrex::Real m_fixed_dt     = -1.0;
    amrex::Real m_init_dt      = -1.0;
+   amrex::Real m_min_dt       = 1.0e-12;
    amrex::Real m_dtshrink     = 1.0;
    amrex::Real m_prev_dt      = -1.0;
    amrex::Real m_dtChangeMax  = 1.1;

Source/PeleLMEvolve.cpp

@@ -55,22 +55,25 @@ void PeleLM::Evolve() {
       doDiagnostics();
 
       // Check message
-      bool dump_and_stop = checkMessage();
+      bool dump_and_stop = checkMessage("dump_and_stop");
+      bool plt_and_continue = checkMessage("plt_and_continue");
+      bool chk_and_continue = checkMessage("chk_and_continue");
 
       // Check for plot file
-      if (writePlotNow() || dump_and_stop) {
+      if (writePlotNow() || dump_and_stop || plt_and_continue)  {
          WritePlotFile();
          plt_justDidIt = 1;
       }
 
-      if (writeCheckNow() || dump_and_stop) {
+      if (writeCheckNow() || dump_and_stop || chk_and_continue) {
          WriteCheckPointFile();
          chk_justDidIt = 1;
       }
 
       // Check for the end of the simulation
       do_not_evolve = ( (m_max_step >= 0 && m_nstep >= m_max_step) ||
                         (m_stop_time >= 0.0 && m_cur_time >= m_stop_time - 1.0e-12 * m_dt) ||
+                        (m_dt < m_min_dt) ||    
                         dump_and_stop );
 
    }
@@ -156,23 +159,35 @@ PeleLM::doTemporalsNow()
 }
 
 bool
-PeleLM::checkMessage()
+PeleLM::checkMessage(const std::string &a_action)
 {
-    bool dump_and_stop = false;
+    bool take_action = false;
+
+    std::string action_file = "";
+    if (a_action == "dump_and_stop") {
+        action_file = "dump_and_stop";
+    } else if (a_action == "plt_and_continue") {
+        action_file = "plt_and_continue";
+    } else if (a_action == "chk_and_continue") {
+        action_file = "chk_and_continue";
+    } else {
+        Abort("Unknown action in checkMessage()");
+    }
+
     if (m_nstep % m_message_int == 0) {
-        int dumpclose = 0;
+        int action_flag = 0;
         if (ParallelDescriptor::IOProcessor()) {
             FILE *fp;
-            if ( (fp=fopen("dump_and_stop","r")) != 0 ) {
-                remove("dump_and_stop");
-                dumpclose = 1;
+            if ( (fp=fopen(action_file.c_str(),"r")) != 0 ) {
+                remove(action_file.c_str());
+                action_flag = 1;
                 fclose(fp);
             }
         }
         int packed_data[1];
-        packed_data[0] = dumpclose;
+        packed_data[0] = action_flag;
         ParallelDescriptor::Bcast(packed_data, 1, ParallelDescriptor::IOProcessorNumber());
-        dump_and_stop = packed_data[0];
+        take_action = packed_data[0];
     }
-    return dump_and_stop;
+    return take_action;
 }

Source/PeleLMSetup.cpp

@@ -400,6 +400,7 @@ void PeleLM::readParameters() {
    ppa.query("dt_shrink", m_dtshrink);
    ppa.query("dt_change_max", m_dtChangeMax);
    ppa.query("max_dt", m_max_dt);
+   ppa.query("min_dt", m_min_dt);
 
    if ( max_level > 0 ) {
       ppa.query("regrid_int", m_regrid_int);

Source/PeleLMTimestep.cpp

@@ -80,6 +80,15 @@ PeleLM::computeDt(int is_init,
       }
    }
 
+   if (estdt < m_min_dt) {
+      Print() << "\n";
+      Print() << " ###################################### \n";
+      Print() << " Estimated dt " << estdt << " is below allowed dt_min "
+              << m_min_dt << ": the simulation will stop ! \n";
+      Print() << " ###################################### \n";
+      Print() << "\n";
+   }
+
    return estdt;
 }