changes to use new MDI library functions

examples/mdi/in.aimd.driver.plugin

@@ -23,7 +23,7 @@ fix		1 all nve
 # NPT
 #fix             1 all npt temp 1.0 1.0 0.1 iso 1.0 1.0 1.0
 
-fix             2 all mdi/aimd plugin
+fix             2 all mdi/aimd
 fix_modify      2 energy yes virial yes
 
 thermo_style    custom step temp pe etotal press vol

lib/mdi/Install.py

@@ -34,7 +34,7 @@ make lib-meam args="-m ifort"   # build MEAM lib with custom Makefile.ifort (usi
 
 # settings
 
-version = "1.3.0"
+version = "1.3.1"
 url = "https://github.com/MolSSI-MDI/MDI_Library/archive/v%s.tar.gz" % version
 
 # known checksums for different MDI versions. used to validate the download.

src/MDI/fix_mdi_aimd.cpp

@@ -29,7 +29,7 @@ enum { NATIVE, REAL, METAL };    // LAMMPS units which MDI supports
 
 FixMDIAimd::FixMDIAimd(LAMMPS *lmp, int narg, char **arg) : Fix(lmp, narg, arg)
 {
-  if (narg > 4) error->all(FLERR, "Illegal fix mdi/aimd command");
+  if (narg != 3) error->all(FLERR, "Illegal fix mdi/aimd command");
 
   scalar_flag = 1;
   global_freq = 1;
@@ -38,16 +38,6 @@ FixMDIAimd::FixMDIAimd(LAMMPS *lmp, int narg, char **arg) : Fix(lmp, narg, arg)
   virial_global_flag = 1;
   thermo_energy = thermo_virial = 1;
 
-  // check for plugin arg
-
-  plugin = 0;
-  if (narg == 4) {
-    if (strcmp(arg[3], "plugin") == 0)
-      plugin = 1;
-    else
-      error->all(FLERR, "Illegal fix mdi/aimd command");
-  }
-
   // check requirements for LAMMPS to work with MDI as an engine
 
   if (atom->tag_enable == 0) error->all(FLERR, "Cannot use MDI engine without atom IDs");
@@ -62,6 +52,11 @@ FixMDIAimd::FixMDIAimd(LAMMPS *lmp, int narg, char **arg) : Fix(lmp, narg, arg)
   if (role != MDI_DRIVER)
     error->all(FLERR, "Must invoke LAMMPS as an MDI driver to use fix mdi/aimd");
 
+  // mdicomm will be one-time initialized in init()
+  // cannot be done here for a plugin library, b/c mdi plugin command is later
+
+  mdicomm = MDI_COMM_NULL;
+
   // storage for all atoms
 
   buf3 = buf3all = nullptr;
@@ -78,13 +73,6 @@ FixMDIAimd::FixMDIAimd(LAMMPS *lmp, int narg, char **arg) : Fix(lmp, narg, arg)
 
   unit_conversions();
 
-  // connect to MDI engine, only if engine is stand-alone code
-
-  if (!plugin) {
-    MDI_Accept_communicator(&mdicomm);
-    if (mdicomm <= 0) error->all(FLERR, "Unable to connect to MDI engine");
-  }
-
   nprocs = comm->nprocs;
 }
 
@@ -92,7 +80,8 @@ FixMDIAimd::FixMDIAimd(LAMMPS *lmp, int narg, char **arg) : Fix(lmp, narg, arg)
 
 FixMDIAimd::~FixMDIAimd()
 {
-  // send exit command to engine, only if engine is stand-alone code
+  // send exit command to engine if it is a stand-alone code
+  // for plugin, this happens in MDIPlugin::plugin_wrapper()
 
   if (!plugin) {
     int ierr = MDI_Send_command("EXIT", mdicomm);
@@ -118,6 +107,29 @@ int FixMDIAimd::setmask()
 
 /* ---------------------------------------------------------------------- */
 
+void FixMDIAimd::init()
+{
+  if (mdicomm != MDI_COMM_NULL) return;
+
+  // one-time initialization of mdicomm
+  // plugin = 0/1 if MDI engine is a stand-alone code vs plugin library
+
+  MDI_Get_communicator(&mdicomm,0);
+
+  if (mdicomm == MDI_COMM_NULL) { 
+    plugin = 0;
+    MDI_Accept_communicator(&mdicomm);
+    if (mdicomm <= 0) error->all(FLERR,"Unable to connect to MDI engine");
+  } else {
+    plugin = 1;
+    int method;
+    MDI_Get_method(&method,mdicomm);
+    if (method != MDI_PLUGIN) error->all(FLERR,"MDI internal error");
+  }
+}
+
+/* ---------------------------------------------------------------------- */
+
 void FixMDIAimd::setup(int vflag)
 {
   post_force(vflag);

src/MDI/fix_mdi_aimd.h

@@ -27,14 +27,11 @@ namespace LAMMPS_NS {
 
 class FixMDIAimd : public Fix {
  public:
-  // MDI communicator, public so that LAMMPS can work with a plugin
-
-  MDI_Comm mdicomm;
-
   FixMDIAimd(class LAMMPS *, int, char **);
   ~FixMDIAimd();
   int setmask();
 
+  void init();
   void setup(int);
   void setup_pre_reverse(int, int);
   void pre_reverse(int, int);
@@ -46,6 +43,8 @@ class FixMDIAimd : public Fix {
   int nprocs;
   int plugin;
 
+  MDI_Comm mdicomm;
+
   int eflag_caller;
   double engine_energy;
   int lmpunits;

src/MDI/mdi_plugin.cpp

@@ -92,11 +92,6 @@ MDIPlugin::MDIPlugin(LAMMPS *_lmp, int narg, char **arg) : Pointers(_lmp)
     strcat(plugin_args, extra_arg);
   }
 
-  // find FixMDIAimd instance so can reset its mdicomm
-  // NOTE: this is a kludge - need better way to handle this
-
-  fixptr = modify->get_fix_by_style("mdi/aimd")[0];
-
   // launch the MDI plugin library
   // path for lib was specified in -mdi command-line arg when LAMMPS started
   // this calls back to plugin_wrapper, which must issue MDI EXIT at end
@@ -108,8 +103,7 @@ MDIPlugin::MDIPlugin(LAMMPS *_lmp, int narg, char **arg) : Pointers(_lmp)
 
 /* ----------------------------------------------------------------------
    callback function from MDI_Launch_plugin()
-   this function must wrap entire interaction of LAMMPS as a driver
-     with the plugin
+   this function wraps entire interaction of LAMMPS driver with the plugin
 ---------------------------------------------------------------------- */
 
 int MDIPlugin::plugin_wrapper(void * /*pmpicomm*/, MDI_Comm mdicomm, void *vptr)
@@ -118,11 +112,6 @@ int MDIPlugin::plugin_wrapper(void * /*pmpicomm*/, MDI_Comm mdicomm, void *vptr)
   LAMMPS *lammps = ptr->lmp;
   char *lammps_command = ptr->lammps_command;
 
-  // set FixMDIAimd mdicomm to driver's mdicomm passed to this callback
-
-  auto aimdptr = dynamic_cast<FixMDIAimd *> (ptr->fixptr);
-  aimdptr->mdicomm = mdicomm;
-
   // invoke the specified LAMMPS command
   // that operation will issue MDI commands to the plugin engine
 

src/MDI/mdi_plugin.h

@@ -25,7 +25,6 @@ class MDIPlugin : protected Pointers {
 
  private:
   char *lammps_command;
-  class Fix *fixptr;
 
   static int plugin_wrapper(void *, MDI_Comm, void *);
 };