add new API to library interface lammps_get_thermo(). include support in python wrapper, too.

python/examples/demo.py

@@ -39,6 +39,9 @@ print("Energy from equal-style variable =",eng)
 vy = lmp.extract_variable("vy","all",1)
 print("Velocity component from atom-style variable =",vy[1])
 
+vol = lmp.get_thermo("vol")
+print("Volume from get_thermo = ",vol)
+
 natoms = lmp.get_natoms()
 print("Natoms from get_natoms =",natoms)
 

python/lammps.py

@@ -248,6 +248,13 @@ class lammps(object):
     if value: value = str(value).encode()
     return self.lib.lammps_set_variable(self.lmp,name,str(value))
 
+  # return current value of thermo keyword
+
+  def get_thermo(self,name):
+    if name: name = name.encode()
+    self.lib.lammps_get_thermo.restype = c_double
+    return self.lib.lammps_get_thermo(self.lmp,name)
+
   # return total number of atoms in system
 
   def get_natoms(self):

src/library.cpp

@@ -28,6 +28,8 @@
 #include "input.h"
 #include "variable.h"
 #include "modify.h"
+#include "output.h"
+#include "thermo.h"
 #include "compute.h"
 #include "fix.h"
 #include "comm.h"
@@ -387,6 +389,23 @@ int lammps_set_variable(void *ptr, char *name, char *str)
   return err;
 }
 
+/* ----------------------------------------------------------------------
+   return the current value of a thermo keyword as double.
+   unlike lammps_extract_global() this does not give access to the
+   storage of the data in question, and thus needs to be called
+   again to retrieve an updated value. The upshot is that it allows
+   accessing information that is only computed on-the-fly.
+------------------------------------------------------------------------- */
+
+double lammps_get_thermo(void *ptr, char *name)
+{
+  LAMMPS *lmp = (LAMMPS *) ptr;
+  double dval;
+
+  lmp->output->thermo->evaluate_keyword(name,&dval);
+  return dval;
+}
+
 /* ----------------------------------------------------------------------
    return the total number of atoms in the system
    useful before call to lammps_get_atoms() so can pre-allocate vector

src/library.h

@@ -39,7 +39,9 @@ void *lammps_extract_fix(void *, char *, int, int, int, int);
 void *lammps_extract_variable(void *, char *, char *);
 
 int lammps_set_variable(void *, char *, char *);
+double lammps_get_thermo(void *, char *);
 int lammps_get_natoms(void *);
+
 void lammps_gather_atoms(void *, char *, int, int, void *);
 void lammps_scatter_atoms(void *, char *, int, int, void *);