support setting global virial for fix external from python

python/lammps/core.py

@@ -1795,20 +1795,38 @@ class lammps(object):
   # -------------------------------------------------------------------------
 
   def fix_external_set_energy_global(self, fix_id, eng):
-    """Get access to that array with per-atom forces of a fix external instance with a given fix ID.
+    """Set the global energy contribution for a fix external instance with the given ID.
 
-    This is a wrapper around the :cpp:func:`lammps_fix_external_get_force` function
+    This is a wrapper around the :cpp:func:`lammps_fix_external_set_energy_global` function
     of the C-library interface.
 
     :param fix_id:  Fix-ID of a fix external instance
     :type: string
-    :param eng:     potential energy to be added by fix external
+    :param eng:     potential energy value to be added by fix external
     :type: float
     """
 
     with ExceptionCheck(self):
       return self.lib.lammps_fix_external_set_energy_global(self.lmp, fix_id.encode(), eng)
 
+  # -------------------------------------------------------------------------
+
+  def fix_external_set_virial_global(self, fix_id, virial):
+    """Set the global virial contribution for a fix external instance with the given ID.
+
+    This is a wrapper around the :cpp:func:`lammps_fix_external_set_virial_global` function
+    of the C-library interface.
+
+    :param fix_id:  Fix-ID of a fix external instance
+    :type: string
+    :param eng:     list of 6 floating point numbers with the virial to be added by fix external
+    :type: float
+    """
+
+    cvirial = (6*c_double)(*virial)
+    with ExceptionCheck(self):
+      return self.lib.lammps_fix_external_set_virial_global(self.lmp, fix_id.encode(), cvirial)
+
   # -------------------------------------------------------------------------
   def fix_external_set_vector_length(self, fix_id, length):
     """Set the vector length for a global vector stored with fix external for analysis

src/library.cpp

@@ -5103,7 +5103,7 @@ void lammps_fix_external_set_vector_length(void *handle, const char *id, int len
   END_CAPTURE
 }
 
-/** Store global vector for a fix external instance with the given ID.
+/** Store a global vector value for a fix external instance with the given ID.
 
 \verbatim embed:rst
 

unittest/python/python-fix-external.py

@@ -4,6 +4,8 @@ from lammps import lammps, LMP_STYLE_GLOBAL, LMP_TYPE_VECTOR
 
 # add timestep dependent force
 def callback_one(lmp, ntimestep, nlocal, tag, x, f):
+    virial = [1.0, 1.0, 1.0, 0.0, 0.0, 0.0]
+    lmp.fix_external_set_virial_global("ext",virial)
     for i in range(nlocal):
         f[i][0] = float(ntimestep)
         f[i][1] = float(ntimestep)
@@ -49,6 +51,7 @@ class PythonExternal(unittest.TestCase):
         lmp.command("run 10 post no")
         self.assertAlmostEqual(lmp.get_thermo("temp"),1.0/30.0,14)
         self.assertAlmostEqual(lmp.get_thermo("pe"),1.0/8.0,14)
+        self.assertAlmostEqual(lmp.get_thermo("press"),0.15416666666666667,14)
         val = 0.0
         for i in range(0,6):
             val += lmp.extract_fix("ext",LMP_STYLE_GLOBAL,LMP_TYPE_VECTOR,nrow=i)