Merge branch 'develop' into fortran-expansion

.github/ISSUE_TEMPLATE/help_request.md

@@ -1,6 +1,6 @@
 ---
 name: Request for Help
-about: "Don't post help requests here, email the lammps-users mailing list"
+about: "Don't post help requests here, post in the LAMMPS forum"
 title: ""
 labels: invalid
 assignees: ''
@@ -8,8 +8,9 @@ assignees: ''
 ---
 
 Please **do not** post requests for help (e.g. with installing or using LAMMPS) here.
-Instead send an e-mail to the lammps-users mailing list.
+Instead, you can post to the LAMMPS category in the Materials Science Community
+Discourse forum at: https://matsci.org/lammps/
 
 This issue tracker is for tracking LAMMPS development related issues only.
 
-Thanks for your cooperation.
+Thank you in advance for your cooperation.

doc/src/Library.rst

@@ -2,12 +2,13 @@ LAMMPS Library Interfaces
 *************************
 
 As described on the :doc:`library interface to LAMMPS <Howto_library>`
-page, LAMMPS can be built as a library (static or shared), so that
+page, LAMMPS can be built as a library (static or shared), so that it
-it can be called by another code, used in a :doc:`coupled manner
+can be called by another code, used in a :doc:`coupled manner
 <Howto_couple>` with other codes, or driven through a :doc:`Python
-script <Python_head>`.  Even the LAMMPS standalone executable is
+script <Python_head>`.  The LAMMPS standalone executable itself is
-essentially a thin wrapper on top of the LAMMPS library, creating a
+essentially a thin wrapper on top of the LAMMPS library, which creates a
-LAMMPS instance, processing input and then existing.
+LAMMPS instance, passes the input for processing to that instance, and
+then exits.
 
 Most of the APIs described below are based on C language wrapper
 functions in the files ``src/library.h`` and ``src/library.cpp``, but
@@ -87,6 +88,18 @@ run LAMMPS in serial mode.
    message retrieved <lammps_get_last_error_message>`.  We thus
    recommend enabling C++ exceptions when using the library interface,
 
+.. admonition:: Using the C library interface as a plugin
+   :class: note
+
+   Rather than including the C library directly and link to the LAMMPS
+   library at compile time, you can use the ``liblammpsplugin.h`` header
+   file and the ``liblammpsplugin.c`` C code in the
+   ``examples/COUPLE/plugin`` folder for an interface to LAMMPS that is
+   largely identical to the regular library interface, only that it will
+   load a LAMMPS shared library file at runtime.  This can be useful for
+   applications where the interface to LAMMPS would be an optional
+   feature.
+
 .. warning::
 
    No checks are made on the arguments of the function calls of the C
@@ -163,5 +176,3 @@ The following links provide some examples and references to the C++ API.
    :maxdepth: 1
 
    Cplusplus
-
-

doc/src/pair_pace.rst

@@ -112,7 +112,7 @@ requests to compute `gamma`, as shown in example below:
     compute max_pace_gamma all reduce max f_pace_gamma
     variable dump_skip equal "c_max_pace_gamma < 5"
 
-    dump pace_dump all custom 20 extrapolative_structures.dump id x y z f_pace_gamma
+    dump pace_dump all custom 20 extrapolative_structures.dump id type x y z f_pace_gamma
     dump_modify pace_dump skip v_dump_skip
 
     variable max_pace_gamma equal c_max_pace_gamma

examples/COUPLE/plugin/.gitignore

@@ -0,0 +1 @@
+/build

examples/COUPLE/plugin/CMakeLists.txt

@@ -0,0 +1,47 @@
+##########################################
+# CMake build system for coupling to the LAMMPS library
+# where the library is loaded dynamically at runtime.
+##########################################
+
+cmake_minimum_required(VERSION 3.10)
+
+# enforce out-of-source build
+if(${CMAKE_SOURCE_DIR} STREQUAL ${CMAKE_BINARY_DIR})
+  message(FATAL_ERROR "In-source builds are not allowed. You must create and use a build directory. "
+    "Please remove CMakeCache.txt and CMakeFiles first.")
+endif()
+
+project(liblammpsplugin VERSION 1.0 LANGUAGES C)
+
+# by default, install into $HOME/.local (not /usr/local),
+# so that no root access (and sudo) is needed
+if(CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
+   set(CMAKE_INSTALL_PREFIX "$ENV{HOME}/.local" CACHE PATH "Default install path" FORCE)
+endif()
+
+# ugly hacks for MSVC which by default always reports an old C++ standard in the __cplusplus macro
+# and prints lots of pointless warnings about "unsafe" functions
+if(MSVC)
+  if(CMAKE_C_COMPILER_ID STREQUAL "MSVC")
+    if(LAMMPS_EXCEPTIONS)
+      add_compile_options(/EHsc)
+    endif()
+  endif()
+  add_compile_definitions(_CRT_SECURE_NO_WARNINGS)
+endif()
+
+find_package(MPI REQUIRED)
+# do not include the (obsolete) MPI C++ bindings which makes
+# for leaner object files and avoids namespace conflicts
+set(MPI_CXX_SKIP_MPICXX TRUE)
+
+##########################
+
+add_executable(simple-plugin simple.c liblammpsplugin.c)
+target_link_libraries(simple-plugin PRIVATE MPI::MPI_C)
+target_compile_definitions(simple-plugin PRIVATE LAMMPS_LIB_MPI)
+
+# link with -ldl or equivalent for plugin loading; except on Windows
+if(NOT ${CMAKE_SYSTEM_NAME} STREQUAL "Windows")
+   target_link_libraries(simple-plugin PRIVATE ${CMAKE_DL_LIBS})
+endif()

examples/COUPLE/plugin/README

@@ -11,32 +11,39 @@ liblammpsplugin.c  is the LAMMPS library plugin loader
 You can then build the driver executable codes with a compile line
 like below.
 
-mpicc -c -O -Wall -g -I$HOME/lammps/src liblammpsplugin.c
+mpicc -c -O -DLAMMPS_LIB_MPI -Wall -g liblammpsplugin.c
-mpicc -c -O -Wall -g simple.c
+mpicc -c -O -DLAMMPS_LIB_MPI -Wall -g simple.c
-mpicc simple.o liblammpsplugin.o -ldl -o simpleC
+mpicc simple.o liblammpsplugin.o -ldl -o simple-plugin
+
+or using the provided CMake file with:
+
+mkdir build
+cd build
+cmake ../
+cmake --build .
 
 You also need to build LAMMPS as a shared library
-(see examples/COUPLE/README), e.g. 
+(see examples/COUPLE/README), e.g.
 
 cd $HOME/lammps/src
 make mode=shlib mpi
 
-or 
+or
 
 cd $HOME/lammps
 mkdir build-shared
 cd build-shared
-cmake -D BUILD_LIB=on -D BUILD_SHARED_LIBS=on ../cmake
+cmake -D BUILD_MPI=on -D BUILD_SHARED_LIBS=on ../cmake
 make
 
-You then run simpleC on a parallel machine
+You then run simple-plugin on a parallel machine
 on some number of processors Q with 3 arguments:
 
-% mpirun -np Q simpleC P in.lj $HOME/lammps/src/liblammps.so
+% mpirun -np Q simple-plugin P in.lj $HOME/lammps/src/liblammps.so
 
 or
 
-% mpirun -np Q simpleC P in.lj $HOME/lammps/build-shared/liblammps.so
+% mpirun -np Q simple-plugin P in.lj $HOME/lammps/build-shared/liblammps.so
 
 P is the number of procs you want LAMMPS to run on (must be <= Q) and
 in.lj is a LAMMPS input script and the last argument is the path to

examples/COUPLE/plugin/liblammpsplugin.c

@@ -18,10 +18,29 @@
    a LAMMPS plugin to some other software.
 */
 
-#include "library.h"
 #include "liblammpsplugin.h"
-#include <stdlib.h>
+
+#if defined(_WIN32)
+
+#ifndef WIN32_LEAN_AND_MEAN
+#define WIN32_LEAN_AND_MEAN
+#endif
+
+#if defined(_WIN32_WINNT)
+#undef _WIN32_WINNT
+#endif
+
+// target Windows version is windows 7 and later
+#define _WIN32_WINNT _WIN32_WINNT_WIN7
+#define PSAPI_VERSION 2
+
+#include <windows.h>
+#else
 #include <dlfcn.h>
+#endif
+
+#include <stdlib.h>
+
 
 liblammpsplugin_t *liblammpsplugin_load(const char *lib)
 {
@@ -29,14 +48,29 @@ liblammpsplugin_t *liblammpsplugin_load(const char *lib)
   void *handle;
 
   if (lib == NULL) return NULL;
+
+#ifdef _WIN32
+  handle = (void *) LoadLibrary(lib);
+#else
   handle = dlopen(lib,RTLD_NOW|RTLD_GLOBAL);
+#endif
   if (handle == NULL) return NULL;
 
   lmp = (liblammpsplugin_t *) malloc(sizeof(liblammpsplugin_t));
   lmp->handle = handle;
 
-#define ADDSYM(symbol) lmp->symbol = dlsym(handle,"lammps_" #symbol)
+#ifdef _WIN32
+#define ADDSYM(symbol) *(void **) (&lmp->symbol) = (void *) GetProcAddress((HINSTANCE) handle, "lammps_" #symbol)
+#else
+#define ADDSYM(symbol) *(void **) (&lmp->symbol) = dlsym(handle,"lammps_" #symbol)
+#endif
+
+#if defined(LAMMPS_LIB_MPI)
   ADDSYM(open);
+#else
+  lmp->open = NULL;
+#endif
+
   ADDSYM(open_no_mpi);
   ADDSYM(open_fortran);
   ADDSYM(close);
@@ -46,6 +80,8 @@ liblammpsplugin_t *liblammpsplugin_load(const char *lib)
   ADDSYM(kokkos_finalize);
   ADDSYM(python_finalize);
 
+  ADDSYM(error);
+
   ADDSYM(file);
   ADDSYM(command);
   ADDSYM(commands_list);
@@ -70,6 +106,7 @@ liblammpsplugin_t *liblammpsplugin_load(const char *lib)
   ADDSYM(extract_compute);
   ADDSYM(extract_fix);
   ADDSYM(extract_variable);
+  ADDSYM(extract_variable_datatype);
   ADDSYM(set_variable);
 
   ADDSYM(gather_atoms);
@@ -77,8 +114,15 @@ liblammpsplugin_t *liblammpsplugin_load(const char *lib)
   ADDSYM(gather_atoms_subset);
   ADDSYM(scatter_atoms);
   ADDSYM(scatter_atoms_subset);
+
   ADDSYM(gather_bonds);
 
+  ADDSYM(gather);
+  ADDSYM(gather_concat);
+  ADDSYM(gather_subset);
+  ADDSYM(scatter);
+  ADDSYM(scatter_subset);
+
   ADDSYM(create_atoms);
 
   ADDSYM(find_pair_neighlist);
@@ -116,6 +160,9 @@ liblammpsplugin_t *liblammpsplugin_load(const char *lib)
   ADDSYM(plugin_count);
   ADDSYM(plugin_name);
 
+  ADDSYM(encode_image_flags);
+  ADDSYM(decode_image_flags);
+
   ADDSYM(set_fix_external_callback);
   ADDSYM(fix_external_get_force);
   ADDSYM(fix_external_set_energy_global);
@@ -125,6 +172,8 @@ liblammpsplugin_t *liblammpsplugin_load(const char *lib)
   ADDSYM(fix_external_set_vector_length);
   ADDSYM(fix_external_set_vector);
 
+  ADDSYM(flush_buffers);
+
   ADDSYM(free);
 
   ADDSYM(is_running);
@@ -139,6 +188,8 @@ liblammpsplugin_t *liblammpsplugin_load(const char *lib)
   lmp->has_error = NULL;
   lmp->get_last_error_message = NULL;
 #endif
+
+  ADDSYM(python_api_version);
   return lmp;
 }
 
@@ -147,7 +198,11 @@ int liblammpsplugin_release(liblammpsplugin_t *lmp)
   if (lmp == NULL) return 1;
   if (lmp->handle == NULL) return 2;
 
+#ifdef _WIN32
+  FreeLibrary((HINSTANCE) handle);
+#else
   dlclose(lmp->handle);
+#endif
   free((void *)lmp);
   return 0;
 }

examples/COUPLE/plugin/liblammpsplugin.h

@@ -28,11 +28,71 @@
 #define LAMMPS_SMALLBIG
 #endif
 
+#if defined(LAMMPS_LIB_MPI)
 #include <mpi.h>
-#if defined(LAMMPS_BIGBIG) || defined(LAMMPS_SMALLBIG)
-#include <inttypes.h>  /* for int64_t */
 #endif
 
+#if defined(LAMMPS_BIGBIG) || defined(LAMMPS_SMALLBIG)
+#include <stdint.h>  /* for int64_t */
+#endif
+
+/* The following must be kept in sync with the equivalent constants in
+ *  python/lammps/constants.py, fortran/lammps.f90, tools/swig/lammps.i,
+ *  and examples/COUPLE/plugin/liblammpsplugin.h */
+
+/* Data type constants for extracting data from atoms, computes and fixes */
+
+enum _LMP_DATATYPE_CONST {
+  LAMMPS_INT = 0,       /*!< 32-bit integer (array) */
+  LAMMPS_INT_2D = 1,    /*!< two-dimensional 32-bit integer array */
+  LAMMPS_DOUBLE = 2,    /*!< 64-bit double (array) */
+  LAMMPS_DOUBLE_2D = 3, /*!< two-dimensional 64-bit double array */
+  LAMMPS_INT64 = 4,     /*!< 64-bit integer (array) */
+  LAMMPS_INT64_2D = 5,  /*!< two-dimensional 64-bit integer array */
+  LAMMPS_STRING = 6     /*!< C-String */
+};
+
+/* Style constants for extracting data from computes and fixes. */
+
+enum _LMP_STYLE_CONST {
+  LMP_STYLE_GLOBAL = 0, /*!< return global data */
+  LMP_STYLE_ATOM = 1,   /*!< return per-atom data */
+  LMP_STYLE_LOCAL = 2   /*!< return local data */
+};
+
+/* Type and size constants for extracting data from computes and fixes. */
+
+enum _LMP_TYPE_CONST {
+  LMP_TYPE_SCALAR = 0, /*!< return scalar */
+  LMP_TYPE_VECTOR = 1, /*!< return vector */
+  LMP_TYPE_ARRAY = 2,  /*!< return array */
+  LMP_SIZE_VECTOR = 3, /*!< return length of vector */
+  LMP_SIZE_ROWS = 4,   /*!< return number of rows */
+  LMP_SIZE_COLS = 5    /*!< return number of columns */
+};
+
+/* Error codes to select the suitable function in the Error class */
+
+enum _LMP_ERROR_CONST {
+  LMP_ERROR_WARNING = 0, /*!< call Error::warning() */
+  LMP_ERROR_ONE = 1,     /*!< called from one MPI rank */
+  LMP_ERROR_ALL = 2,     /*!< called from all MPI ranks */
+  LMP_ERROR_WORLD = 4,   /*!< error on Comm::world */
+  LMP_ERROR_UNIVERSE = 8 /*!< error on Comm::universe */
+};
+
+/** Variable style constants for extracting data from variables.
+ *
+ * Must be kept in sync with the equivalent constants in python/lammps/constants.py,
+ * fortran/lammps.f90, and tools/swig/lammps.i */
+
+enum _LMP_VAR_CONST {
+  LMP_VAR_EQUAL = 0,  /*!< compatible with equal-style variables */
+  LMP_VAR_ATOM = 1,   /*!< compatible with atom-style variables */
+  LMP_VAR_VECTOR = 2, /*!< compatible with vector-style variables */
+  LMP_VAR_STRING = 3  /*!< return value will be a string (catch-all) */
+};
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -49,7 +109,11 @@ struct _liblammpsplugin {
   int abiversion;
   int has_exceptions;
   void *handle;
+#if defined(LAMMPS_LIB_MPI)
   void *(*open)(int, char **, MPI_Comm, void **);
+#else
+  void *open;
+#endif
   void *(*open_no_mpi)(int, char **, void **);
   void *(*open_fortran)(int, char **, void **, int);
   void (*close)(void *);
@@ -59,13 +123,15 @@ struct _liblammpsplugin {
   void (*kokkos_finalize)();
   void (*python_finalize)();
 
+  void (*error)(void *, int, const char *);
+
   void (*file)(void *, char *);
   char *(*command)(void *, const char *);
   void (*commands_list)(void *, int, const char **);
   void (*commands_string)(void *, const char *);
 
   double (*get_natoms)(void *);
-  double (*get_thermo)(void *, char *);
+  double (*get_thermo)(void *, const char *);
 
   void (*extract_box)(void *, double *, double *,
                       double *, double *, double *, int *, int *);
@@ -78,12 +144,13 @@ struct _liblammpsplugin {
   int *(*extract_global_datatype)(void *, const char *);
   void *(*extract_global)(void *, const char *);
 
-  void *(*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);
   void *(*extract_fix)(void *, const char *, int, int, int, int);
   void *(*extract_variable)(void *, const char *, char *);
+  int (*extract_variable_datatype)(void *, const char *);
   int (*set_variable)(void *, char *, char *);
 
   void (*gather_atoms)(void *, char *, int, int, void *);
@@ -93,22 +160,26 @@ struct _liblammpsplugin {
   void (*scatter_atoms_subset)(void *, char *, int, int, int, int *, void *);
 
   void (*gather_bonds)(void *, void *);
-  
+
-// lammps_create_atoms() takes tagint and imageint as args
+  void (*gather)(void *, char *, int, int, void *);
-// ifdef insures they are compatible with rest of LAMMPS
+  void (*gather_concat)(void *, char *, int, int, void *);
-// caller must match to how LAMMPS library is built
+  void (*gather_subset)(void *, char *, int, int, int, int *,void *);
+  void (*scatter)(void *, char *, int, int, void *);
+  void (*scatter_subset)(void *, char *, int, int, int, int *, void *);
+
+/* lammps_create_atoms() takes tagint and imageint as args
+ * the ifdef insures they are compatible with rest of LAMMPS
+ * caller must match to how LAMMPS library is built */
 
 #ifndef LAMMPS_BIGBIG
- void (*create_atoms)(void *, int, int *, int *, double *,
+ void (*create_atoms)(void *, int, int *, int *, double *, double *, int *, int);
-                      double *, int *, int);
 #else
-  void (*create_atoms)(void *, int, int64_t *, int *, double *,
+  void (*create_atoms)(void *, int, int64_t *, int *, double *, double *, int64_t *, int);
-                       double *, int64_t *, int);
 #endif
 
   int (*find_pair_neighlist)(void *, const char *, int, int, int);
   int (*find_fix_neighlist)(void *, const char *, int);
-  int (*find_compute_neighlist)(void *, char *, int);
+  int (*find_compute_neighlist)(void *, const char *, int);
   int (*neighlist_num_elements)(void *, int);
   void (*neighlist_element_neighbors)(void *, int, int, int *, int *, int **);
 
@@ -141,8 +212,16 @@ struct _liblammpsplugin {
   int (*plugin_count)();
   int (*plugin_name)(int, char *, char *, int);
 
-  void (*set_fix_external_callback)(void *, const char *, FixExternalFnPtr, void*);
+#if !defined(LAMMPS_BIGBIG)
-  void (*fix_external_get_force)(void *, const char *);
+  int (*encode_image_flags)(int, int, int);
+  void (*decode_image_flags)(int, int *);
+#else
+  int64_t (*encode_image_flags)(int, int, int);
+  void (*decode_image_flags)(int64_t, int *);
+#endif
+
+  void (*set_fix_external_callback)(void *, const char *, FixExternalFnPtr, void *);
+  double **(*fix_external_get_force)(void *, const char *);
   void (*fix_external_set_energy_global)(void *, const char *, double);
   void (*fix_external_set_energy_peratom)(void *, const char *, double *);
   void (*fix_external_set_virial_global)(void *, const char *, double *);
@@ -150,6 +229,8 @@ struct _liblammpsplugin {
   void (*fix_external_set_vector_length)(void *, const char *, int);
   void (*fix_external_set_vector)(void *, const char *, int, double);
 
+  void (*flush_buffers)(void *);
+
   void (*free)(void *);
 
   void (*is_running)(void *);
@@ -157,6 +238,8 @@ struct _liblammpsplugin {
 
   int (*has_error)(void *);
   int (*get_last_error_message)(void *, char *, int);
+
+  int (*python_api_version)();
 };
 
 typedef struct _liblammpsplugin liblammpsplugin_t;

examples/COUPLE/plugin/simple.c

@@ -19,10 +19,16 @@
            in.lammps = LAMMPS input script
    See README for compilation instructions */
 
+#include <mpi.h>
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
-#include <mpi.h>
+
+/* define so interface to lammps_open() is available,
+   since we will run on split communicator */
+#define LAMMPS_LIB_MPI 1
+
 #include "liblammpsplugin.h"  /* this is the include for the plugin loader */
 
 int main(int narg, char **arg)
@@ -87,7 +93,13 @@ int main(int narg, char **arg)
       MPI_Abort(MPI_COMM_WORLD,1);
     }
   }
-  if (lammps == 1) lmp = plugin->open(0,NULL,comm_lammps,NULL);
+  if (lammps == 1) {
+    if (plugin->open == NULL) {
+      printf("ERROR: liblammpsmpi.c must be compiled with -DLAMMPS_LIB_MPI=1 for this program\n");
+      MPI_Abort(MPI_COMM_WORLD,2);
+    }
+    lmp = plugin->open(0,NULL,comm_lammps,NULL);
+  }
 
   while (1) {
     if (me == 0) {
@@ -112,23 +124,23 @@ int main(int narg, char **arg)
 
     int natoms = plugin->get_natoms(lmp);
     x = (double *) malloc(3*natoms*sizeof(double));
-    plugin->gather_atoms(lmp,"x",1,3,x);
+    plugin->gather_atoms(lmp,(char *)"x",1,3,x);
     v = (double *) malloc(3*natoms*sizeof(double));
-    plugin->gather_atoms(lmp,"v",1,3,v);
+    plugin->gather_atoms(lmp,(char *)"v",1,3,v);
     double epsilon = 0.1;
     x[0] += epsilon;
-    plugin->scatter_atoms(lmp,"x",1,3,x);
+    plugin->scatter_atoms(lmp,(char *)"x",1,3,x);
 
     plugin->command(lmp,"run 1");
   }
 
-  // extract force on single atom two different ways
+  /* extract force on single atom two different ways */
 
   if (lammps == 1) {
     double **f = (double **) plugin->extract_atom(lmp,"f");
     printf("Force on 1 atom via extract_atom: %g\n",f[0][0]);
 
-    double *fx = (double *) plugin->extract_variable(lmp,"fx","all");
+    double *fx = (double *) plugin->extract_variable(lmp,"fx",(char *)"all");
     printf("Force on 1 atom via extract_variable: %g\n",fx[0]);
   }
 
@@ -160,7 +172,7 @@ int main(int narg, char **arg)
   if (v) free(v);
   if (type) free(type);
 
-  // close down LAMMPS
+  /* close down LAMMPS */
 
   if (lammps == 1) {
     plugin->close(lmp);

examples/COUPLE/simple/CMakeLists.txt

@@ -1,17 +1,44 @@
 cmake_minimum_required(VERSION 3.10)
-project(simple CXX)
 
-set(LAMMPS_SRC_DIRECTORY "" CACHE PATH "Path for lammps source")
+# enforce out-of-source build
-if(NOT LAMMPS_SRC_DIRECTORY STREQUAL "" AND EXISTS ${LAMMPS_SRC_DIRECTORY}/cmake/CMakeLists.txt)
+if(${CMAKE_SOURCE_DIR} STREQUAL ${CMAKE_BINARY_DIR})
-  option(BUILD_LIB "Build LAMMPS library" ON)
+  message(FATAL_ERROR "In-source builds are not allowed. You must create and use a build directory. "
-  add_subdirectory(${LAMMPS_SRC_DIRECTORY}/cmake lammps)
+    "Please remove CMakeCache.txt and CMakeFiles first.")
-else()
+endif()
+
+project(couple-simple VERSION 1.0 LANGUAGES C CXX)
+
+# by default, install into $HOME/.local (not /usr/local),
+# so that no root access (and sudo) is needed
+if(CMAKE_INSTALL_PREFIX_INITIALIZED_TO_DEFAULT)
+   set(CMAKE_INSTALL_PREFIX "$ENV{HOME}/.local" CACHE PATH "Default install path" FORCE)
+endif()
+
+# ugly hacks for MSVC which by default always reports an old C++ standard in the __cplusplus macro
+# and prints lots of pointless warnings about "unsafe" functions
+if(MSVC)
+  if(CMAKE_C_COMPILER_ID STREQUAL "MSVC")
+    if(LAMMPS_EXCEPTIONS)
+      add_compile_options(/EHsc)
+    endif()
+  endif()
+  add_compile_definitions(_CRT_SECURE_NO_WARNINGS)
+endif()
+
+find_package(MPI QUIET)
+# do not include the (obsolete) MPI C++ bindings which makes
+# for leaner object files and avoids namespace conflicts
+set(MPI_CXX_SKIP_MPICXX TRUE)
+
+##########################
+
+# build within LAMMPS build system
+if(NOT LAMMPS_SOURCE_DIR)
   find_package(LAMMPS REQUIRED)
 endif()
 
 add_executable(simpleCC simple.cpp)
 target_link_libraries(simpleCC LAMMPS::lammps)
 
-enable_language(C)
 add_executable(simpleC simple.c)
 target_link_libraries(simpleC LAMMPS::lammps)

fortran/lammps.f90

@@ -44,7 +44,8 @@ MODULE LIBLAMMPS
   ! Data type constants for extracting data from global, atom, compute, and fix
   !
   ! Must be kept in sync with the equivalent declarations in
-  ! src/library.h, python/lammps/constants.py, and tools/swig/lammps.i
+  ! src/library.h, python/lammps/constants.py, tools/swig/lammps.i,
+  ! and examples/COUPLE/plugin/liblammpsplugin.h
   !
   ! These are NOT part of the API (the part the user sees)
   INTEGER(c_int), PARAMETER :: &

python/lammps/constants.py

@@ -22,8 +22,8 @@ LAMMPS_INT64       = 4
 LAMMPS_INT64_2D    = 5
 LAMMPS_STRING      = 6
 
-# these must be kept in sync with the enums in src/library.h, tools/swig/lammps.i
+# these must be kept in sync with the enums in src/library.h, tools/swig/lammps.i,
-# and the constants in fortran/lammps.f90
+# examples/COUPLE/plugin/liblammpsplugin.h, and the constants in fortran/lammps.f90
 LMP_STYLE_GLOBAL   = 0
 LMP_STYLE_ATOM     = 1
 LMP_STYLE_LOCAL    = 2

src/fix_pair.cpp

@@ -240,15 +240,19 @@ void FixPair::post_force(int /*vflag*/)
   // extract pair style fields one by one
   // store their values in this fix
 
-  int nlocal = atom->nlocal;
+  const int nlocal = atom->nlocal;
 
   int icol = 0;
   int columns;
 
   for (int ifield = 0; ifield < nfield; ifield++) {
     void *pvoid = pstyle->extract_peratom(fieldname[ifield],columns);
-    if (pvoid == nullptr)
+
-      error->all(FLERR,"Fix pair pair style cannot extract {}",fieldname[ifield]);
+    // Pair::extract_peratom() may return a null pointer if there are no atoms the sub-domain
+    // so returning null is only an error if there are local atoms.
+
+    if ((pvoid == nullptr) && (nlocal > 0))
+      error->one(FLERR, "Fix pair cannot extract property {} from pair style", fieldname[ifield]);
 
     if (columns == 0) {
       double *pvector = (double *) pvoid;

src/library.h

@@ -41,7 +41,7 @@
 /** Data type constants for extracting data from atoms, computes and fixes
  *
  * Must be kept in sync with the equivalent constants in python/lammps/constants.py,
- * fortran/lammps.f90, and tools/swig/lammps.i */
+ * fortran/lammps.f90, tools/swig/lammps.i, examples/COUPLE/plugin/liblammpsplugin.h */
 
 enum _LMP_DATATYPE_CONST {
   LAMMPS_INT = 0,       /*!< 32-bit integer (array) */
@@ -56,7 +56,7 @@ enum _LMP_DATATYPE_CONST {
 /** Style constants for extracting data from computes and fixes.
  *
  * Must be kept in sync with the equivalent constants in python/lammps/constants.py,
- * fortran/lammps.f90, and tools/swig/lammps.i */
+ * fortran/lammps.f90, tools/swig/lammps.i, and examples/COUPLE/plugin/liblammpsplugin.h */
 
 enum _LMP_STYLE_CONST {
   LMP_STYLE_GLOBAL = 0, /*!< return global data */
@@ -67,7 +67,7 @@ enum _LMP_STYLE_CONST {
 /** Type and size constants for extracting data from computes and fixes.
  *
  * Must be kept in sync with the equivalent constants in python/lammps/constants.py,
- * fortran/lammps.f90, and tools/swig/lammps.i */
+ * fortran/lammps.f90, tools/swig/lammps.i, and examples/COUPLE/plugin/liblammpsplugin.h */
 
 enum _LMP_TYPE_CONST {
   LMP_TYPE_SCALAR = 0, /*!< return scalar */
@@ -81,7 +81,7 @@ enum _LMP_TYPE_CONST {
 /** Error codes to select the suitable function in the Error class
  *
  * Must be kept in sync with the equivalent constants in python/lammps/constants.py,
- * fortran/lammps.f90, and tools/swig/lammps.i */
+ * fortran/lammps.f90, tools/swig/lammps.i, and examples/COUPLE/plugin/liblammpsplugin.h */
 
 enum _LMP_ERROR_CONST {
   LMP_ERROR_WARNING = 0, /*!< call Error::warning() */
@@ -94,7 +94,7 @@ enum _LMP_ERROR_CONST {
 /** Variable style constants for extracting data from variables.
  *
  * Must be kept in sync with the equivalent constants in python/lammps/constants.py,
- * fortran/lammps.f90, and tools/swig/lammps.i */
+ * fortran/lammps.f90, tools/swig/lammps.i, and examples/COUPLE/plugin/liblammpsplugin.h */
 
 enum _LMP_VAR_CONST {
   LMP_VAR_EQUAL = 0,  /*!< compatible with equal-style variables */
@@ -260,15 +260,14 @@ void lammps_decode_image_flags(int64_t image, int *flags);
 
 #if defined(LAMMPS_BIGBIG)
 typedef void (*FixExternalFnPtr)(void *, int64_t, int, int64_t *, double **, double **);
-void lammps_set_fix_external_callback(void *handle, const char *id, FixExternalFnPtr funcptr,
-                                      void *ptr);
 #elif defined(LAMMPS_SMALLBIG)
 typedef void (*FixExternalFnPtr)(void *, int64_t, int, int *, double **, double **);
-void lammps_set_fix_external_callback(void *, const char *, FixExternalFnPtr, void *);
 #else
 typedef void (*FixExternalFnPtr)(void *, int, int, int *, double **, double **);
-void lammps_set_fix_external_callback(void *, const char *, FixExternalFnPtr, void *);
 #endif
+
+void lammps_set_fix_external_callback(void *handle, const char *id, FixExternalFnPtr funcptr,
+                                      void *ptr);
 double **lammps_fix_external_get_force(void *handle, const char *id);
 void lammps_fix_external_set_energy_global(void *handle, const char *id, double eng);
 void lammps_fix_external_set_energy_peratom(void *handle, const char *id, double *eng);

unittest/c-library/CMakeLists.txt

@@ -71,3 +71,23 @@ add_executable(test_library_mpi test_library_mpi.cpp)
 target_link_libraries(test_library_mpi PRIVATE lammps GTest::GMock)
 target_compile_definitions(test_library_mpi PRIVATE ${TEST_CONFIG_DEFS})
 add_mpi_test(NAME LibraryMPI NUM_PROCS 4 COMMAND $<TARGET_FILE:test_library_mpi>)
+
+# simple run tests for coupling to the LAMMPS library
+if(BUILD_MPI)
+  if(BUILD_SHARED_LIBS)
+    add_subdirectory(${LAMMPS_DIR}/examples/COUPLE/plugin ${CMAKE_BINARY_DIR}/build-couple)
+    add_test(NAME RunCoupleSimplePlugin
+      COMMAND $<TARGET_FILE:simple-plugin> 1 ${LAMMPS_DIR}/examples/COUPLE/plugin/in.lj $<TARGET_FILE:lammps>)
+    set_tests_properties(RunCoupleSimplePlugin PROPERTIES
+      ENVIRONMENT "TSAN_OPTIONS=ignore_noninstrumented_modules=1;HWLOC_HIDE_ERRORS=2"
+      PASS_REGULAR_EXPRESSION "LAMMPS \\([0-9]+ [A-Za-z]+ 2[0-9][0-9][0-9]( - Update [0-9]+)?\\)")
+  endif()
+  add_subdirectory(${LAMMPS_DIR}/examples/COUPLE/simple ${CMAKE_BINARY_DIR}/build-simple)
+  add_test(NAME RunCoupleSimpleC
+    COMMAND $<TARGET_FILE:simpleC> 1 ${LAMMPS_DIR}/examples/COUPLE/simple/in.lj)
+  add_test(NAME RunCoupleSimpleCC
+    COMMAND $<TARGET_FILE:simpleCC> 1 ${LAMMPS_DIR}/examples/COUPLE/simple/in.lj)
+  set_tests_properties(RunCoupleSimpleC RunCoupleSimpleCC PROPERTIES
+    ENVIRONMENT "TSAN_OPTIONS=ignore_noninstrumented_modules=1;HWLOC_HIDE_ERRORS=2"
+    PASS_REGULAR_EXPRESSION "LAMMPS \\([0-9]+ [A-Za-z]+ 2[0-9][0-9][0-9]( - Update [0-9]+)?\\)")
+endif()