add API to library interface to access last thermo data

src/EXTRA-DUMP/dump_yaml.cpp

@@ -61,8 +61,8 @@ void DumpYAML::write_header(bigint ndump)
   if (thermo) {
     Thermo *th = output->thermo;
     // output thermo data only on timesteps where it was computed
-    if (update->ntimestep == th->get_timestep()) {
+    if (update->ntimestep == *th->get_timestep()) {
-      int nfield = th->get_nfield();
+      int nfield = *th->get_nfield();
       const auto &keywords = th->get_keywords();
       const auto &fields = th->get_fields();
 

src/NETCDF/dump_netcdf.cpp

@@ -224,7 +224,7 @@ void DumpNetCDF::openfile()
 
   if (thermo && !singlefile_opened) {
     delete[] thermovar;
-    thermovar = new int[output->thermo->get_nfield()];
+    thermovar = new int[*output->thermo->get_nfield()];
   }
 
   // now the computes and fixes have been initialized, so we can query
@@ -323,7 +323,7 @@ void DumpNetCDF::openfile()
       if (thermo) {
         Thermo *th = output->thermo;
         const auto &keywords = th->get_keywords();
-        const int nfield = th->get_nfield();
+        const int nfield = *th->get_nfield();
 
         for (int i = 0; i < nfield; i++) {
           NCERRX( nc_inq_varid(ncid, keywords[i].c_str(), &thermovar[i]), keywords[i].c_str() );
@@ -439,7 +439,7 @@ void DumpNetCDF::openfile()
         Thermo *th = output->thermo;
         const auto &fields = th->get_fields();
         const auto &keywords = th->get_keywords();
-        const int nfield = th->get_nfield();
+        const int nfield = *th->get_nfield();
 
         for (int i = 0; i < nfield; i++) {
           if (fields[i].type == multitype::DOUBLE) {
@@ -610,18 +610,18 @@ void DumpNetCDF::write()
     // will output current thermo data only on timesteps where it was computed.
     // warn (once) about using cached copy from old timestep.
 
-    if (thermo_warn && (update->ntimestep != th->get_timestep())) {
+    if (thermo_warn && (update->ntimestep != *th->get_timestep())) {
       thermo_warn = false;
       if (comm->me == 0) {
         error->warning(FLERR, "Dump {} output on incompatible timestep with thermo output: {} vs {} \n"
                        "         Dump netcdf always stores thermo data from last thermo output",
-                       id, th->get_timestep(), update->ntimestep);
+                       id, *th->get_timestep(), update->ntimestep);
       }
     }
 
     const auto &keywords = th->get_keywords();
     const auto &fields = th->get_fields();
-    int nfield = th->get_nfield();
+    int nfield = *th->get_nfield();
     for (int i = 0; i < nfield; i++) {
       if (filewriter) {
         if (fields[i].type == multitype::DOUBLE) {

src/NETCDF/dump_netcdf_mpiio.cpp

@@ -221,7 +221,7 @@ void DumpNetCDFMPIIO::openfile()
 
   if (thermo && !singlefile_opened) {
     delete[] thermovar;
-    thermovar = new int[output->thermo->get_nfield()];
+    thermovar = new int[*output->thermo->get_nfield()];
   }
 
   // now the computes and fixes have been initialized, so we can query
@@ -321,7 +321,7 @@ void DumpNetCDFMPIIO::openfile()
     if (thermo) {
       Thermo *th = output->thermo;
       const auto &keywords = th->get_keywords();
-      const int nfield = th->get_nfield();
+      const int nfield = *th->get_nfield();
 
       for (int i = 0; i < nfield; i++) {
         NCERRX( ncmpi_inq_varid(ncid, keywords[i].c_str(), &thermovar[i]), keywords[i].c_str() );
@@ -429,7 +429,7 @@ void DumpNetCDFMPIIO::openfile()
       Thermo *th = output->thermo;
       const auto &fields = th->get_fields();
       const auto &keywords = th->get_keywords();
-      const int nfield = th->get_nfield();
+      const int nfield = *th->get_nfield();
 
       for (int i = 0; i < nfield; i++) {
         if (fields[i].type == multitype::DOUBLE) {
@@ -603,18 +603,18 @@ void DumpNetCDFMPIIO::write()
     // will output current thermo data only on timesteps where it was computed.
     // warn (once) about using cached copy from old timestep.
 
-    if (thermo_warn && (update->ntimestep != th->get_timestep())) {
+    if (thermo_warn && (update->ntimestep != *th->get_timestep())) {
       thermo_warn = false;
       if (comm->me == 0) {
         error->warning(FLERR, "Dump {} output on incompatible timestep with thermo output: {} vs {} \n"
                        "         Dump netcdf/mpiio always stores thermo data from last thermo output",
-                       id, th->get_timestep(), update->ntimestep);
+                       id, *th->get_timestep(), update->ntimestep);
       }
     }
 
     const auto &keywords = th->get_keywords();
     const auto &fields = th->get_fields();
-    int nfield = th->get_nfield();
+    int nfield = *th->get_nfield();
     for (int i = 0; i < nfield; i++) {
       if (filewriter) {
         if (fields[i].type == multitype::DOUBLE) {

src/library.cpp

@@ -719,7 +719,7 @@ double lammps_get_natoms(void *handle)
 
 /* ---------------------------------------------------------------------- */
 
-/** Get current value of a thermo keyword.
+/** Evaluate a thermo keyword.
  *
 \verbatim embed:rst
 
@@ -750,6 +750,103 @@ double lammps_get_thermo(void *handle, const char *keyword)
 
 /* ---------------------------------------------------------------------- */
 
+/** Access cached data from last thermo output
+ *
+\verbatim embed:rst
+
+This function provides access to cached data from the last thermo
+output.  This differs from :cpp:func:`lammps_get_thermo` in that it does
+not trigger an evaluation.  It provides direct access to a a read-only
+location of the last thermo output data and the corresponding keyword
+strings. The output depends on the value of the *what* argument string.
+
+.. list-table::
+   :header-rows: 1
+   :widths: auto
+
+   * - Value of *what
+     - Description of return value
+     - Data type
+     - Uses index
+   * - step
+     - timestep when the last thermo output was generated or -1 when no data available
+     - pointer to bigint cast to void pointer
+     - no
+   * - num
+     - number of fields in thermo output
+     - pointer to int cast to void pointer
+     - no
+   * - keyword
+     - column keyword for thermo output
+     - const char pointer cast to void pointer
+     - yes
+   * - type
+     - data type of thermo output column. LAMMPS_INT, LAMMPS_DOUBLE, or LAMMPS_INT64
+     - const int cast to void pointer
+     - yes
+   * - data
+     - actual field data for column
+     - pointer to either int, int64_t or double cast to void pointer
+     - yes
+     
+\endverbatim
+ *
+ * \param  handle   pointer to a previously created LAMMPS instance
+ * \param  what     string with the kind of data requested
+ * \param  idx      integer with index into data arrays, ignored for scalar data
+ * \return          pointer to location of requested data cast to void or NULL */
+
+void *lammps_last_thermo(void *handle, const char *what, int idx)
+{
+  auto lmp = (LAMMPS *) handle;
+  void *val = nullptr;
+  Thermo *th = lmp->output->thermo;
+  if (!th) return nullptr;
+  const int nfield = *th->get_nfield();
+
+  BEGIN_CAPTURE
+  {
+    if (strcmp(what, "step") == 0) {
+      val = (void *) th->get_timestep();
+
+    } else if (strcmp(what, "num") == 0) {
+      val = (void *) th->get_nfield();
+
+    } else if (strcmp(what, "keyword") == 0) {
+      if ((idx < 0) || (idx >= nfield)) return nullptr;
+      const auto &keywords = th->get_keywords();
+      val = (void *) keywords[idx].c_str();
+
+    } else if (strcmp(what, "type") == 0) {
+      if ((idx < 0) || (idx >= nfield)) return nullptr;
+      const auto &field = th->get_fields()[idx];
+      if (field.type == multitype::INT) {
+        val = (void *) LAMMPS_INT;
+      } else if (field.type == multitype::BIGINT) {
+        val = (void *) LAMMPS_INT64;
+      } else if (field.type == multitype::DOUBLE) {
+        val = (void *) LAMMPS_DOUBLE;
+      }
+
+    } else if (strcmp(what, "data") == 0) {
+      if ((idx < 0) || (idx >= nfield)) return nullptr;
+      const auto &field = th->get_fields()[idx];
+      if (field.type == multitype::INT) {
+        val = (void *) &field.data.i;
+      } else if (field.type == multitype::BIGINT) {
+        val = (void *) &field.data.b;
+      } else if (field.type == multitype::DOUBLE) {
+        val = (void *) &field.data.d;
+      }
+
+    } else val = nullptr;
+  }
+  END_CAPTURE
+  return val;
+}
+
+/* ---------------------------------------------------------------------- */
+
 /** Extract simulation box parameters.
  *
 \verbatim embed:rst

src/library.h

@@ -148,6 +148,7 @@ void lammps_commands_string(void *handle, const char *str);
 
 double lammps_get_natoms(void *handle);
 double lammps_get_thermo(void *handle, const char *keyword);
+void *lammps_last_thermo(void *handle, const char *what, int idx);
 
 void lammps_extract_box(void *handle, double *boxlo, double *boxhi, double *xy, double *yz,
                         double *xz, int *pflags, int *boxflag);

src/thermo.cpp

@@ -111,6 +111,7 @@ Thermo::Thermo(LAMMPS *_lmp, int narg, char **arg) :
   lostflag = lostbond = Thermo::ERROR;
   lostbefore = warnbefore = 0;
   flushflag = 0;
+  ntimestep = -1;
 
   // set style and corresponding lineflag
   // custom style builds its own line of keywords, including wildcard expansion

src/thermo.h

@@ -43,8 +43,8 @@ class Thermo : protected Pointers {
   int evaluate_keyword(const std::string &, double *);
 
   // for accessing cached thermo data
-  int get_nfield() const { return nfield; }
+  const int *get_nfield() const { return &nfield; }
-  bigint get_timestep() const { return ntimestep; }
+  const bigint *get_timestep() const { return &ntimestep; }
   const std::vector<multitype> &get_fields() const { return field_data; }
   const std::vector<std::string> &get_keywords() const { return keyword; }