work on model_builder python; support building and testing it in python on bazel

WORKSPACE

@@ -106,3 +106,35 @@ cc_library(
 )
 """
 )
+
+http_archive(
+    name = "rules_python",
+    sha256 = "9fcf91dbcc31fde6d1edb15f117246d912c33c36f44cf681976bd886538deba6",
+    strip_prefix = "rules_python-0.8.0",
+    url = "https://github.com/bazelbuild/rules_python/archive/refs/tags/0.8.0.tar.gz",
+)
+
+load("@rules_python//python:pip.bzl", "pip_install")
+
+# Create a central external repo, @ortools_deps, that contains Bazel targets for all the
+# third-party packages specified in the python_deps.txt file.
+pip_install(
+   name = "ortools_deps",
+   requirements = "//bazel:python_deps.txt",
+)
+
+git_repository(
+    name = "pybind11_bazel",
+    commit = "72cbbf1fbc830e487e3012862b7b720001b70672",
+    remote = "https://github.com/pybind/pybind11_bazel.git",
+)
+
+new_git_repository(
+    name = "pybind11",
+    build_file = "@pybind11_bazel//:pybind11.BUILD",    
+    tag = "v2.9.1",
+    remote = "https://github.com/pybind/pybind11.git",
+)
+
+load("@pybind11_bazel//:python_configure.bzl", "python_configure")
+python_configure(name = "local_config_python", python_version = "3")

bazel/BUILD.bazel

@@ -9,4 +9,5 @@ exports_files([
     "bliss-0.73.patch",
     #    "zlib.BUILD",
     "archive_helper.bzl",
+    "python_deps.txt",
 ])

bazel/python_deps.txt

@@ -0,0 +1,3 @@
+absl-py >= 0.13
+numpy >= 1.13.3
+protobuf >= 3.19.4

ortools/linear_solver/BUILD.bazel

@@ -1,5 +1,6 @@
 load("@rules_cc//cc:defs.bzl", "cc_proto_library")
 load("@bazel_skylib//rules:copy_file.bzl", "copy_file")
+load("@com_google_protobuf//:protobuf.bzl", "py_proto_library")
 
 package(default_visibility = ["//visibility:public"])
 
@@ -41,6 +42,13 @@ cc_proto_library(
     deps = [":linear_solver_proto"],
 )
 
+py_proto_library(
+    name = "linear_solver_py_pb2",
+    srcs = ["linear_solver.proto"],
+    deps = ["//ortools/util:optional_boolean_py_pb2"],
+    visibility = ["//visibility:public"],
+)
+
 # You can include the interfaces to different solvers by invoking '--define'
 # flags. By default GLOP, BOP, SCIP, GUROBI, and CP-SAT interface are included.
 #

ortools/linear_solver/sat_proto_solver.cc

@@ -24,6 +24,7 @@
 #include "ortools/sat/cp_model.pb.h"
 #include "ortools/sat/cp_model_solver.h"
 #include "ortools/sat/lp_utils.h"
+#include "ortools/sat/parameters_validation.h"
 #include "ortools/sat/sat_parameters.pb.h"
 #include "ortools/util/logging.h"
 #include "ortools/util/time_limit.h"
@@ -80,13 +81,17 @@ sat::CpSolverStatus FromMPSolverResponseStatus(MPSolverResponseStatus status) {
 
 MPSolutionResponse InfeasibleResponse(SolverLogger& logger,
                                       std::string message) {
+  SOLVER_LOG(&logger, "Infeasible model detected in sat_solve_proto.\n",
+             message);
+
   // This is needed for our benchmark scripts.
-  MPSolutionResponse response;
   if (logger.LoggingIsEnabled()) {
     sat::CpSolverResponse cp_response;
     cp_response.set_status(sat::CpSolverStatus::INFEASIBLE);
     SOLVER_LOG(&logger, CpSolverResponseStats(cp_response));
   }
+
+  MPSolutionResponse response;
   response.set_status(MPSolverResponseStatus::MPSOLVER_INFEASIBLE);
   response.set_status_str(message);
   return response;
@@ -94,13 +99,16 @@ MPSolutionResponse InfeasibleResponse(SolverLogger& logger,
 
 MPSolutionResponse ModelInvalidResponse(SolverLogger& logger,
                                         std::string message) {
+  SOLVER_LOG(&logger, "Invalid input detected in sat_solve_proto.\n", message);
+
   // This is needed for our benchmark scripts.
-  MPSolutionResponse response;
   if (logger.LoggingIsEnabled()) {
     sat::CpSolverResponse cp_response;
     cp_response.set_status(sat::CpSolverStatus::MODEL_INVALID);
     SOLVER_LOG(&logger, CpSolverResponseStats(cp_response));
   }
+
+  MPSolutionResponse response;
   response.set_status(MPSolverResponseStatus::MPSOLVER_MODEL_INVALID);
   response.set_status_str(message);
   return response;
@@ -175,6 +183,14 @@ absl::StatusOr<MPSolutionResponse> SatSolveProto(
     return ModelInvalidResponse(logger, "Extra CP-SAT validation failed.");
   }
 
+  {
+    const std::string error = sat::ValidateParameters(params);
+    if (!error.empty()) {
+      return ModelInvalidResponse(
+          logger, absl::StrCat("Invalid CP-SAT parameters: ", error));
+    }
+  }
+
   // This is good to do before any presolve.
   if (!sat::MakeBoundsOfIntegerVariablesInteger(params, mp_model, &logger)) {
     return InfeasibleResponse(logger,

ortools/model_builder/python/BUILD.bazel

@@ -0,0 +1,44 @@
+# Python wrapper for model_builder.
+
+load("@ortools_deps//:requirements.bzl", "requirement")
+load("@pybind11_bazel//:build_defs.bzl", "pybind_extension")
+load("@rules_python//python:defs.bzl", "py_library")
+
+pybind_extension(
+    name = "pywrap_model_builder_helper",
+    srcs = ["pywrap_model_builder_helper.cc"],
+    visibility = ["//visibility:public"],
+    deps = [
+        "//ortools/linear_solver:linear_solver_cc_proto",
+        "//ortools/linear_solver:model_exporter",
+        "//ortools/model_builder/wrappers:model_builder_helper",
+        "@com_google_absl//absl/strings",
+        "@eigen//:eigen3",
+    ],
+)
+
+py_library(
+    name = "model_builder_helper",
+    srcs = ["model_builder_helper.py"],
+    data = [
+        ":pywrap_model_builder_helper.so",
+    ],
+    visibility = ["//visibility:public"],
+    deps = [
+        requirement("numpy"),
+        "//ortools/linear_solver:linear_solver_py_pb2",
+    ],
+)
+
+py_library(
+    name = "model_builder",
+    srcs = ["model_builder.py"],
+    data = [
+        ":pywrap_model_builder_helper.so",
+    ],
+    visibility = ["//visibility:public"],
+    deps = [
+        ":model_builder_helper",
+        "//ortools/linear_solver:linear_solver_py_pb2",
+    ],
+)

ortools/model_builder/python/model_builder.py

@@ -157,7 +157,7 @@ class LinearExpr(object):
         return _Sum(self, arg)
 
     def __radd__(self, arg):
-        return self.__add(arg)
+        return self.__add__(arg)
 
     def __sub__(self, arg):
         if mbh.is_zero(arg):
@@ -219,8 +219,6 @@ class LinearExpr(object):
     def __eq__(self, arg):
         if arg is None:
             return False
-        if isinstance(self, Variable) and isinstance(arg, Variable):
-            return VarCompVar(self, arg, True)
         if mbh.is_a_number(arg):
             arg = mbh.assert_is_a_number(arg)
             return BoundedLinearExpression(self, arg, arg)
@@ -242,8 +240,6 @@ class LinearExpr(object):
             return BoundedLinearExpression(self - arg, -math.inf, 0)
 
     def __ne__(self, arg):
-        if isinstance(self, Variable) and isinstance(arg, Variable):
-            return VarCompVar(self, arg, False)
         return NotImplemented
 
     def __lt__(self, arg):
@@ -540,6 +536,25 @@ class Variable(LinearExpr):
     def objective_coefficient(self, coeff):
         return self.__helper.set_var_objective_coefficient(self.__index, coeff)
 
+    def __eq__(self, arg):
+        if arg is None:
+            return False
+        if isinstance(arg, Variable):
+            return VarCompVar(self, arg, True)
+        else:
+            if mbh.is_a_number(arg):
+                arg = mbh.assert_is_a_number(arg)
+                return BoundedLinearExpression(self, arg, arg)
+            else:
+                return BoundedLinearExpression(self - arg, 0, 0)
+
+    def __ne__(self, arg):
+        if arg is None:
+            return True
+        if isinstance(arg, Variable):
+            return VarCompVar(self, arg, False)
+        return NotImplemented
+
     def __hash__(self):
         return hash((self.__helper, self.__index))
 
@@ -559,7 +574,7 @@ class VarCompVar(object):
             return f'{self.__left} == {self.__right}'
 
     def __repr__(self):
-        return f'VarEqVar({self.__left}, {self.__right}, {self.__is_equality})'
+        return f'VarCompVar({self.__left}, {self.__right}, {self.__is_equality})'
 
     @property
     def left(self):
@@ -574,7 +589,7 @@ class VarCompVar(object):
         return self.__is_equality
 
     def __bool__(self):
-        return (self.__left == self.__right) == self.__is_equality
+        return (self.__left.index == self.__right.index) == self.__is_equality
 
 
 class BoundedLinearExpression(object):

ortools/model_builder/samples/BUILD.bazel

@@ -1 +1,11 @@
 # Samples code the model builder library.
+
+load(":code_samples.bzl", "code_sample_py")
+
+code_sample_py(name = "assignment_mb")
+
+code_sample_py(name = "bin_packing_mb")
+
+code_sample_py(name = "simple_lp_program_mb")
+
+code_sample_py(name = "simple_mip_program_mb")

ortools/model_builder/samples/code_samples.bzl

@@ -1,5 +1,8 @@
 """Helper macro to compile and test code samples."""
 
+load("@ortools_deps//:requirements.bzl", "requirement")
+load("@rules_python//python:defs.bzl", "py_binary")
+
 def code_sample_cc(name):
   native.cc_binary(
       name = name,
@@ -23,3 +26,26 @@ def code_sample_cc(name):
       ],
   )
 
+def code_sample_py(name):
+    py_binary(
+        name = name + "_py3",
+        srcs = [name + ".py"],
+        main = name + ".py",
+        deps = [
+            requirement("absl-py"),
+            "//ortools/model_builder/python:model_builder",
+        ],
+        python_version = "PY3",
+        srcs_version = "PY3",
+    )
+
+    native.sh_test(
+        name = name + "_py_test",
+        size = "small",
+        srcs = ["code_samples_py_test.sh"],
+        args = [name],
+        data = [
+            ":" + name + "_py3",
+        ],
+    )
+

ortools/model_builder/samples/code_samples_py_test.sh

@@ -0,0 +1,9 @@
+#!/bin/bash
+
+declare -r DIR="${TEST_SRCDIR}/com_google_ortools/ortools/model_builder/samples"
+
+function test::ortools::code_samples_model_builder_py() {
+    "${DIR}/$1_py3"
+}
+
+test::ortools::code_samples_model_builder_py $1

ortools/model_builder/wrappers/BUILD.bazel

@@ -0,0 +1,31 @@
+# ModelBuilder: a lightweight implementation of the linear_solver API
+
+# Public exports.
+exports_files(
+    [
+        "README.md",
+        "BUILD.bazel",
+        "CMakeLists.txt",
+    ] + glob([
+        "*.cc",
+        "*.h",
+    ]),
+)
+
+cc_library(
+    name = "model_builder_helper",
+    srcs = ["model_builder_helper.cc"],
+    hdrs = ["model_builder_helper.h"],
+    visibility = ["//visibility:public"],
+    copts = [
+        "-DUSE_SCIP",
+    ],    
+    deps = [
+        "//ortools/linear_solver",
+        "//ortools/linear_solver:linear_solver_cc_proto",
+        "//ortools/linear_solver:model_exporter",
+        "//ortools/lp_data:lp_parser",
+        "//ortools/lp_data:mps_reader",
+        "//ortools/util:logging",
+    ],
+)

ortools/model_builder/wrappers/model_builder_helper.cc

@@ -269,7 +269,7 @@ void ModelSolverHelper::Solve(const ModelBuilderHelper& model) {
       }
       break;
     }
-#if defined(USE_SCIP)    
+#if defined(USE_SCIP)
     case MPModelRequest::SCIP_MIXED_INTEGER_PROGRAMMING: {
       // TODO(user): Enable log_callback support.
       // TODO(user): Enable interrupt_solve.
@@ -279,7 +279,7 @@ void ModelSolverHelper::Solve(const ModelBuilderHelper& model) {
       }
       break;
     }
-#endif  // defined(USE_SCIP)    
+#endif  // defined(USE_SCIP)
     default: {
       response_->set_status(
           MPSolverResponseStatus::MPSOLVER_SOLVER_TYPE_UNAVAILABLE);