[Bazel] enable highs for linear_solver by default; better support for highs in linear_solver; read .lp file in solve_model.py

ortools/linear_solver/BUILD.bazel

@@ -97,7 +97,7 @@ config_setting(
 
 bool_flag(
     name = "with_highs",
-    build_setting_default = False,
+    build_setting_default = True,
 )
 
 config_setting(
@@ -316,6 +316,12 @@ cc_library(
             "@scip",
         ],
         "//conditions:default": [],
+    })+ select({
+        ":use_highs": [
+            "//ortools/linear_solver/proto_solver:highs_proto_solver",
+            "@highs",
+        ],
+        "//conditions:default": [],
     }),
 )
 

ortools/linear_solver/highs_interface.cc

@@ -114,23 +114,6 @@ MPSolver::ResultStatus HighsInterface::Solve(const MPSolverParameters& param) {
   Reset();
   ExtractModel();
 
-  SetParameters(param);
-  if (quiet_) {
-    // parameters_.set_verbosity_level(0);
-  } else {
-    // parameters_.set_verbosity_level(3);
-  }
-
-  solver_->SetSolverSpecificParametersAsString(
-      solver_->solver_specific_parameter_string_);
-
-  // Time limit.
-  if (solver_->time_limit()) {
-    VLOG(1) << "Setting time limit = " << solver_->time_limit() << " ms.";
-    // parameters_.mutable_termination_criteria()->set_time_sec_limit(
-    //     static_cast<double>(solver_->time_limit()) / 1000.0);
-  }
-
   // Mark variables and constraints as extracted.
   for (int i = 0; i < solver_->variables_.size(); ++i) {
     set_variable_as_extracted(i, true);
@@ -147,6 +130,15 @@ MPSolver::ResultStatus HighsInterface::Solve(const MPSolverParameters& param) {
                               ? MPModelRequest::HIGHS_MIXED_INTEGER_PROGRAMMING
                               : MPModelRequest::HIGHS_LINEAR_PROGRAMMING);
 
+  SetParameters(param);
+  request.set_enable_internal_solver_output(!quiet_);
+  request.set_solver_specific_parameters(
+      solver_->solver_specific_parameter_string_);
+  if (solver_->time_limit()) {
+    request.set_solver_time_limit_seconds(
+        static_cast<double>(solver_->time_limit()) / 1000.0);
+  }
+
   // Set parameters.
   absl::StatusOr<MPSolutionResponse> response =
       HighsSolveProto(std::move(request));

ortools/linear_solver/python/solve_model.py

@@ -32,11 +32,15 @@ def main(argv: Sequence[str]) -> None:
 
     model = model_builder.ModelBuilder()
 
-    # Load MPS or proto file.
+    # Load MPS, LP, or proto file.
     if _INPUT.value.endswith(".mps"):
         if not model.import_from_mps_file(_INPUT.value):
             print(f"Cannot import MPS file: '{_INPUT.value}'")
             return
+    elif _INPUT.value.endswith(".lp"):
+        if not model.import_from_lp_file(_INPUT.value):
+            print(f"Cannot import LP file: '{_INPUT.value}'")
+            return
     elif not model.import_from_proto_file(_INPUT.value):
         print(f"Cannot import Proto file: '{_INPUT.value}'")
         return