Merge pull request #1740 from ERGO-Code/fix-1733

Added setBasis to highspy, both for logical basis and specific basis

examples/call_highs_from_python.py

@@ -197,6 +197,28 @@
 run_time = h.getRunTime()
 print("Total HiGHS run time is ", run_time)
 
+# Get an optimal basis
+
+# Clear so that incumbent model is empty
+h.clear()
+print("25fv47 as HighsModel")
+
+h.readModel("check/instances/25fv47.mps")
+
+h.run()
+simplex_iteration_count = h.getInfo().simplex_iteration_count
+print("From initial basis, simplex iteration count =", simplex_iteration_count)
+basis = h.getBasis()
+h.clearSolver()
+
+h.setBasis(basis)
+h.run()
+simplex_iteration_count = h.getInfo().simplex_iteration_count
+print("From optimal basis, simplex iteration count =", simplex_iteration_count)
+status = h.setBasis()
+h.run()
+simplex_iteration_count = h.getInfo().simplex_iteration_count
+print("From logical basis, simplex iteration count =", simplex_iteration_count)
 
 
 # Define a callback
@@ -316,4 +338,4 @@ def user_interrupt_callback(
 print("...")
 for icol in range(num_var-2, num_var):
     print(icol, solution.col_value[icol],
-          h.basisStatusToString(basis.col_status[icol]))
+          h.basisStatusToString(basis.col_status[icol]))

src/highs_bindings.cpp

@@ -285,6 +285,14 @@ HighsStatus highs_deleteRows(Highs* h, HighsInt num_set_entries, std::vector<Hig
     return h->deleteRows(num_set_entries, indices.data());
 }
 
+HighsStatus highs_setBasis(Highs* h, HighsBasis& basis) {
+  return h->setBasis(basis);
+}
+
+HighsStatus highs_setLogicalBasis(Highs* h) {
+  return h->setBasis();
+}
+
 std::tuple<HighsStatus, py::object> highs_getOptionValue(
     Highs* h, const std::string& option) {
   HighsOptionType option_type;
@@ -927,6 +935,8 @@ PYBIND11_MODULE(_core, m) {
       .def("deleteVars", &highs_deleteCols) // alias
       .def("deleteRows", &highs_deleteRows)
       .def("setSolution", &Highs::setSolution)
+      .def("setBasis", &highs_setBasis)
+      .def("setBasis", &highs_setLogicalBasis)
       .def("modelStatusToString", &Highs::modelStatusToString)
       .def("solutionStatusToString", &Highs::solutionStatusToString)
       .def("basisStatusToString", &Highs::basisStatusToString)