add lammps_extract_pair_dimension and lammps_extract_pair to library interface

examples/COUPLE/plugin/liblammpsplugin.c

@@ -101,6 +101,8 @@ liblammpsplugin_t *liblammpsplugin_load(const char *lib)
   ADDSYM(extract_setting);
   ADDSYM(extract_global_datatype);
   ADDSYM(extract_global);
+  ADDSYM(extract_pair_dimension);
+  ADDSYM(extract_pair);
   ADDSYM(map_atom);
 
   ADDSYM(extract_atom_datatype);

examples/COUPLE/plugin/liblammpsplugin.h

@@ -144,11 +144,13 @@ struct _liblammpsplugin {
   int (*get_mpi_comm)(void *);
 
   int (*extract_setting)(void *, const char *);
-  int *(*extract_global_datatype)(void *, const char *);
+  int (*extract_global_datatype)(void *, const char *);
   void *(*extract_global)(void *, const char *);
-  void *(*map_atom)(void *, const void *);
+  int (*extract_pair_dimension)(void *, const char *);
+  void *(*extract_pair)(void *, const char *);
+  int (*map_atom)(void *, const void *);
 
-  int *(*extract_atom_datatype)(void *, const char *);
+  int (*extract_atom_datatype)(void *, const char *);
   void *(*extract_atom)(void *, const char *);
 
   void *(*extract_compute)(void *, const char *, int, int);

python/lammps/core.py

@@ -267,6 +267,9 @@ class lammps(object):
     self.lib.lammps_extract_global.argtypes = [c_void_p, c_char_p]
     self.lib.lammps_extract_global_datatype.argtypes = [c_void_p, c_char_p]
     self.lib.lammps_extract_global_datatype.restype = c_int
+    self.lib.lammps_extract_pair.argtypes = [c_void_p, c_char_p]
+    self.lib.lammps_extract_pair_dimension.argtypes = [c_void_p, c_char_p]
+    self.lib.lammps_extract_pair_dimension.restype = c_int
     self.lib.lammps_extract_compute.argtypes = [c_void_p, c_char_p, c_int, c_int]
 
     self.lib.lammps_map_atom.argtypes = [c_void_p, c_void_p]
@@ -848,7 +851,7 @@ class lammps(object):
     This function returns ``None`` if the keyword is not
     recognized. Otherwise it will return a positive integer value that
     corresponds to one of the :ref:`data type <py_datatype_constants>`
-    constants define in the :py:mod:`lammps` module.
+    constants defined in the :py:mod:`lammps` module.
 
     :param name: name of the property
     :type name:  string
@@ -931,6 +934,96 @@ class lammps(object):
       else: return target_type(ptr[0])
     return None
 
+  # -------------------------------------------------------------------------
+  # extract pair property dimensionality
+
+  def extract_pair_dimension(self, name):
+    """Retrieve pair style  property dimensionality from LAMMPS
+
+    This is a wrapper around the :cpp:func:`lammps_extract_pair_dimension`
+    function of the C-library interface. The list of supported keywords
+    depends on the pair style. This function returns ``None`` if the keyword
+    is not recognized.
+
+    :param name: name of the property
+    :type name:  string
+    :return: dimensionality of the extractable data (typically 0, 1, or 2)
+    :rtype: int
+    """
+    if name:
+      name = name.encode()
+    else:
+      return None
+    dim = self.lib.lammps_extract_pair_dimension(self.lmp, name)
+
+    if dim < 0:
+      return None
+    else:
+      return dim;
+
+  # -------------------------------------------------------------------------
+  # get access to pair style extractable data
+
+  def extract_pair(self, name):
+    """Extract pair style data from LAMMPS.
+
+    This is a wrapper around the :cpp:func:`lammps_extract_pair` function
+    of the C-library interface.  Since there are no pointers in Python, this
+    method will - unlike the C function - return the value or a list of
+    values.
+    Since Python needs to know the dimensionality to be able to interpret
+    the result, this function will detect the dimensionality by asking the library.
+    This function returns ``None`` if the keyword is not recognized.
+
+    :param name: name of the property
+    :type name:  string
+    :return: value of the property or list of values or None
+    :rtype: float, list of float, list of list of floats, or NoneType
+    """
+
+    if name:
+      name = name.encode()
+    else:
+      return None
+
+    dim = self.extract_pair_dimension(name)
+    if dim == None:
+      return None
+    elif dim == 0:
+      self.lib.lammps_extract_pair.restype = POINTER(c_double)
+    elif dim == 1:
+      self.lib.lammps_extract_pair.restype = POINTER(c_double)
+    elif dim == 2:
+      self.lib.lammps_extract_pair.restype = POINTER(POINTER(c_double))
+    else:
+      return None
+
+    ntypes = self.extract_setting('ntypes')
+    ptr = self.lib.lammps_extract_pair(self.lmp, name)
+    if ptr:
+      if dim == 0:
+        return float(ptr[0])
+      elif dim == 1:
+        result = [0.0]
+        for i in range(1,ntypes+1):
+          result.append(float(ptr[i]))
+        return result
+      elif dim == 2:
+        result = []
+        inner = []
+        for i in range(0,ntypes+1):
+          inner.append(float(0.0))
+        result.append(inner)
+        for i in range(1,ntypes+1):
+          inner = [0.0]
+          for j in range(1,ntypes+1):
+            inner.append(float(ptr[i][j]))
+          result.append(inner)
+        return result
+      else:
+        return None
+    return None
+
   # -------------------------------------------------------------------------
   # map global atom ID to local atom index
 

src/library.cpp

@@ -42,6 +42,7 @@
 #include "neigh_list.h"
 #include "neighbor.h"
 #include "output.h"
+#include "pair.h"
 #if defined(LMP_PLUGIN)
 #include "plugin.h"
 #endif
@@ -1938,6 +1939,69 @@ void *lammps_extract_global(void *handle, const char *name)
 
 /* ---------------------------------------------------------------------- */
 
+/** Get data dimension of pair style data accesible via Pair::extract().
+ *
+\verbatim embed:rst
+
+.. versionadded:: TBD
+
+This function returns an integer that specified the dimensionality of
+the data that can be extracted from the current pair style with ``Pair::extract()``.
+Callers of :cpp:func:`lammps_extract_pair` can use this information
+to then decide how to cast the ``void *`` pointer and access the data.
+
+\endverbatim
+ *
+ * \param  handle   pointer to a previously created LAMMPS instance
+ * \param  name     string with the name of the extracted property
+ * \return          integer constant encoding the dimensionality of the
+                    extractable pair style property or -1 if not found. */
+
+int lammps_extract_pair_dimension(void * handle, const char *name)
+{
+  auto lmp = (LAMMPS *) handle;
+  if (!lmp) return -1;
+  auto pair = lmp->force->pair;
+  if (!pair) return -1;
+
+  int dim = -1;
+  if (lmp->force->pair->extract(name, dim)) return dim;
+
+  return -1;
+}
+
+/* ---------------------------------------------------------------------- */
+
+/** Get extract pair style data accesible via Pair::extract().
+ *
+\verbatim embed:rst
+
+.. versionadded:: TBD
+
+This function returns a pointer to data available from the current pair
+style with ``Pair::extract()``. The dimensionality of the returned
+pointer can be determined with :cpp:func:`lammps_extract_pair_dimension`.
+
+\endverbatim
+ *
+ * \param  handle   pointer to a previously created LAMMPS instance
+ * \param  name     string with the name of the extracted property
+ * \return          pointer (cast to ``void *``) to the location of the
+                    requested property. NULL if name is not known. */
+
+void *lammps_extract_pair(void * handle, const char *name)
+{
+  auto lmp = (LAMMPS *) handle;
+  if (!lmp) return nullptr;
+  auto pair = lmp->force->pair;
+  if (!pair) return nullptr;
+
+  int dim = -1;
+  return lmp->force->pair->extract(name, dim);
+}
+
+/* ---------------------------------------------------------------------- */
+
 /** Map global atom ID to local atom index
  *
 \verbatim embed:rst

src/library.h

@@ -162,6 +162,9 @@ int lammps_extract_setting(void *handle, const char *keyword);
 int lammps_extract_global_datatype(void *handle, const char *name);
 void *lammps_extract_global(void *handle, const char *name);
 
+int lammps_extract_pair_dimension(void *handle, const char *name);
+void *lammps_extract_pair(void *handle, const char *name);
+
 int lammps_map_atom(void *handle, const void *id);
 
 /* ----------------------------------------------------------------------

tools/swig/lammps.i

@@ -125,6 +125,8 @@ extern int    lammps_get_mpi_comm(void *handle);
 extern int    lammps_extract_setting(void *handle, const char *keyword);
 extern int    lammps_extract_global_datatype(void *handle, const char *name);
 extern void  *lammps_extract_global(void *handle, const char *name);
+extern int    lammps_extract_pair_dimension(void *handle, const char *name);
+extern void  *lammps_extract_pair(void *handle, const char *name);
 extern int    lammps_map_atom(void *handle, const void *id);
 
 extern int    lammps_extract_atom_datatype(void *handle, const char *name);
@@ -311,6 +313,8 @@ extern int    lammps_get_mpi_comm(void *handle);
 extern int    lammps_extract_setting(void *handle, const char *keyword);
 extern int    lammps_extract_global_datatype(void *handle, const char *name);
 extern void  *lammps_extract_global(void *handle, const char *name);
+extern int    lammps_extract_pair_dimension(void *handle, const char *name);
+extern void  *lammps_extract_pair(void *handle, const char *name);
 extern int    lammps_map_atom(void *handle, const void *id);
 
 extern int    lammps_extract_atom_datatype(void *handle, const char *name);