diff --git a/ortools/constraint_solver/local_search.cc b/ortools/constraint_solver/local_search.cc
index 088205cfa6..3dace2fbc9 100644
--- a/ortools/constraint_solver/local_search.cc
+++ b/ortools/constraint_solver/local_search.cc
@@ -2162,7 +2162,9 @@ class MultiArmedBanditCompoundOperator : public LocalSearchOperator {
   // Sets how often we explore rarely used and unsuccessful in the past
   // operators. Operators are sorted by
   //  avg_improvement_[i] + exploration_coefficient_ *
-  //   sqrt(2 * log(1 + num_neighbors_) / (1 + num_neighbors_per_operator_[i]));
+  //   sqrt(2 * log(1 + num_neighbors_) / (1 + num_neighbors_per_operator_[i])).
+  // This definition uses the UCB1 exploration bonus for unstructured
+  // multi-armed bandits.
   const double exploration_coefficient_;
 };
 
diff --git a/ortools/constraint_solver/python/pywrapcp_util.h b/ortools/constraint_solver/python/pywrapcp_util.h
index 46d64b4ec2..c792581396 100644
--- a/ortools/constraint_solver/python/pywrapcp_util.h
+++ b/ortools/constraint_solver/python/pywrapcp_util.h
@@ -92,4 +92,5 @@ class CallPyDecisionBuilder : public operations_research::DecisionBuilder {
   PyObject* str_func_;
 };
 
+
 #endif  // OR_TOOLS_CONSTRAINT_SOLVER_PYTHON_PYWRAPCP_UTIL_H_
diff --git a/ortools/constraint_solver/samples/BUILD.bazel b/ortools/constraint_solver/samples/BUILD.bazel
index 1f940e1706..75440f8d58 100644
--- a/ortools/constraint_solver/samples/BUILD.bazel
+++ b/ortools/constraint_solver/samples/BUILD.bazel
@@ -2,6 +2,8 @@ load(":code_samples.bzl", "code_sample_cc")
 
 code_sample_cc(name = "minimal_jobshop_cp")
 
+code_sample_cc(name = "nqueens_cp")
+
 code_sample_cc(name = "nurses_cp")
 
 code_sample_cc(name = "rabbits_and_pheasants_cp")
@@ -20,12 +22,12 @@ code_sample_cc(name = "tsp_cities")
 
 code_sample_cc(name = "tsp_distance_matrix")
 
+code_sample_cc(name = "vrp")
+
 code_sample_cc(name = "vrp_breaks")
 
 code_sample_cc(name = "vrp_capacity")
 
-code_sample_cc(name = "vrp")
-
 code_sample_cc(name = "vrp_drop_nodes")
 
 code_sample_cc(name = "vrp_global_span")
diff --git a/ortools/constraint_solver/samples/code_samples.bzl b/ortools/constraint_solver/samples/code_samples.bzl
index 7a7240df59..6f838b54b0 100644
--- a/ortools/constraint_solver/samples/code_samples.bzl
+++ b/ortools/constraint_solver/samples/code_samples.bzl
@@ -1,28 +1,29 @@
 """Helper macro to compile and test code samples."""
 
 def code_sample_cc(name):
-    native.cc_binary(
-        name = name,
-        srcs = [name + ".cc"],
-        deps = [
-            "//ortools/base",
-            "//ortools/constraint_solver:cp",
-            "//ortools/constraint_solver:routing",
-            "//ortools/constraint_solver:routing_enums_cc_proto",
-            "//ortools/constraint_solver:routing_flags",
-        ],
-    )
+  native.cc_binary(
+      name = name,
+      srcs = [name + ".cc"],
+      deps = [
+        "//ortools/base",
+        "//ortools/constraint_solver:cp",
+        "//ortools/constraint_solver:routing",
+        "//ortools/constraint_solver:routing_enums_cc_proto",
+        "//ortools/constraint_solver:routing_flags",
+      ],
+  )
+
+  native.cc_test(
+      name = name+"_test",
+      size = "small",
+      srcs = [name + ".cc"],
+      deps = [
+        ":"+name,
+        "//ortools/base",
+        "//ortools/constraint_solver:cp",
+        "//ortools/constraint_solver:routing",
+        "//ortools/constraint_solver:routing_enums_cc_proto",
+        "//ortools/constraint_solver:routing_flags",
+      ],
+  )
 
-    native.cc_test(
-        name = name + "_test",
-        size = "small",
-        srcs = [name + ".cc"],
-        deps = [
-            ":" + name,
-            "//ortools/base",
-            "//ortools/constraint_solver:cp",
-            "//ortools/constraint_solver:routing",
-            "//ortools/constraint_solver:routing_enums_cc_proto",
-            "//ortools/constraint_solver:routing_flags",
-        ],
-    )
diff --git a/ortools/constraint_solver/samples/cp_is_fun_cp.cc b/ortools/constraint_solver/samples/cp_is_fun_cp.cc
index e089a0eefb..746951b7a2 100644
--- a/ortools/constraint_solver/samples/cp_is_fun_cp.cc
+++ b/ortools/constraint_solver/samples/cp_is_fun_cp.cc
@@ -22,6 +22,10 @@
 #include <cstdint>
 #include <vector>
 
+#include "absl/flags/flag.h"
+#include "ortools/base/init_google.h"
+#include "ortools/base/logging.h"
+#include "ortools/base/logging_flags.h"
 #include "ortools/constraint_solver/constraint_solver.h"
 // [END import]
 
@@ -153,6 +157,8 @@ void CPIsFunCp() {
 }  // namespace operations_research
 
 int main(int argc, char** argv) {
+  InitGoogle(argv[0], &argc, &argv, true);
+  absl::SetFlag(&FLAGS_logtostderr, true);
   operations_research::CPIsFunCp();
   return EXIT_SUCCESS;
 }
diff --git a/ortools/constraint_solver/samples/minimal_jobshop_cp.cc b/ortools/constraint_solver/samples/minimal_jobshop_cp.cc
index b1de44a1d8..6469cdacf9 100644
--- a/ortools/constraint_solver/samples/minimal_jobshop_cp.cc
+++ b/ortools/constraint_solver/samples/minimal_jobshop_cp.cc
@@ -1,4 +1,4 @@
-// Copyright 2018 Google LLC
+// Copyright 2010-2021 Google LLC
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
@@ -13,8 +13,12 @@
 
 #include <iomanip>
 #include <numeric>  // std::iota
+#include <string>
 
+#include "absl/flags/flag.h"
+#include "ortools/base/init_google.h"
 #include "ortools/base/logging.h"
+#include "ortools/base/logging_flags.h"
 #include "ortools/constraint_solver/constraint_solver.h"
 
 // Solve a job shop problem:
@@ -187,8 +191,8 @@ void SolveJobShopExample() {
 }  // namespace operations_research
 
 int main(int argc, char** argv) {
-  google::InitGoogleLogging(argv[0]);
-  absl::SetFlag(&FLAGS_logtostderr, 1);
+  InitGoogle(argv[0], &argc, &argv, true);
+  absl::SetFlag(&FLAGS_logtostderr, true);
   operations_research::SolveJobShopExample();
   return EXIT_SUCCESS;
 }
diff --git a/ortools/constraint_solver/samples/nqueens_cp.cc b/ortools/constraint_solver/samples/nqueens_cp.cc
index e75b44e3bb..62f3dc3c21 100644
--- a/ortools/constraint_solver/samples/nqueens_cp.cc
+++ b/ortools/constraint_solver/samples/nqueens_cp.cc
@@ -19,6 +19,7 @@
 #include <sstream>
 #include <vector>
 
+#include "ortools/base/logging.h"
 #include "ortools/constraint_solver/constraint_solver.h"
 // [END import]
 
diff --git a/ortools/constraint_solver/samples/nurses_cp.cc b/ortools/constraint_solver/samples/nurses_cp.cc
index 790be18211..8d2242e749 100644
--- a/ortools/constraint_solver/samples/nurses_cp.cc
+++ b/ortools/constraint_solver/samples/nurses_cp.cc
@@ -1,4 +1,4 @@
-// Copyright 2018 Google LLC
+// Copyright 2010-2021 Google LLC
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
@@ -13,7 +13,10 @@
 
 #include <numeric>  // std::iota
 
+#include "absl/flags/flag.h"
+#include "ortools/base/init_google.h"
 #include "ortools/base/logging.h"
+#include "ortools/base/logging_flags.h"
 #include "ortools/constraint_solver/constraint_solver.h"
 
 namespace operations_research {
@@ -197,8 +200,8 @@ void SolveNursesExample() {
 }  // namespace operations_research
 
 int main(int argc, char** argv) {
-  google::InitGoogleLogging(argv[0]);
-  absl::SetFlag(&FLAGS_logtostderr, 1);
+  InitGoogle(argv[0], &argc, &argv, true);
+  absl::SetFlag(&FLAGS_logtostderr, true);
   operations_research::SolveNursesExample();
   return EXIT_SUCCESS;
 }
diff --git a/ortools/constraint_solver/samples/rabbits_and_pheasants_cp.cc b/ortools/constraint_solver/samples/rabbits_and_pheasants_cp.cc
index e559b9e555..49d41ba3b6 100644
--- a/ortools/constraint_solver/samples/rabbits_and_pheasants_cp.cc
+++ b/ortools/constraint_solver/samples/rabbits_and_pheasants_cp.cc
@@ -1,4 +1,4 @@
-// Copyright 2018 Google LLC
+// Copyright 2010-2021 Google LLC
 // Licensed under the Apache License, Version 2.0 (the "License");
 // you may not use this file except in compliance with the License.
 // You may obtain a copy of the License at
@@ -13,8 +13,10 @@
 
 // Knowing that we see 20 heads and 56 legs,
 // how many pheasants and rabbits are we looking at ?
-
+#include "absl/flags/flag.h"
+#include "ortools/base/init_google.h"
 #include "ortools/base/logging.h"
+#include "ortools/base/logging_flags.h"
 #include "ortools/constraint_solver/constraint_solver.h"
 
 namespace operations_research {
@@ -57,8 +59,8 @@ void RunConstraintProgrammingExample() {
 }  // namespace operations_research
 
 int main(int argc, char** argv) {
-  google::InitGoogleLogging(argv[0]);
-  absl::SetFlag(&FLAGS_logtostderr, 1);
+  InitGoogle(argv[0], &argc, &argv, true);
+  absl::SetFlag(&FLAGS_logtostderr, true);
   operations_research::RunConstraintProgrammingExample();
   return EXIT_SUCCESS;
 }
diff --git a/ortools/constraint_solver/samples/simple_cp_program.cc b/ortools/constraint_solver/samples/simple_cp_program.cc
index 7c0d88475e..09785929ee 100644
--- a/ortools/constraint_solver/samples/simple_cp_program.cc
+++ b/ortools/constraint_solver/samples/simple_cp_program.cc
@@ -13,6 +13,8 @@
 
 // [START program]
 // [START import]
+#include <string>
+
 #include "ortools/constraint_solver/constraint_solver.h"
 // [END import]
 
diff --git a/ortools/flatzinc/fz.cc b/ortools/flatzinc/fz.cc
index ecfce327a3..84b5d25671 100644
--- a/ortools/flatzinc/fz.cc
+++ b/ortools/flatzinc/fz.cc
@@ -28,9 +28,8 @@
 #include <vector>
 
 #include "absl/flags/flag.h"
-#include "absl/flags/parse.h"
-#include "absl/flags/usage.h"
 #include "ortools/base/commandlineflags.h"
+#include "ortools/base/init_google.h"
 #include "ortools/base/integral_types.h"
 #include "ortools/base/logging.h"
 #include "ortools/base/threadpool.h"
diff --git a/ortools/flatzinc/parser_main.cc b/ortools/flatzinc/parser_main.cc
index a4435742ae..48439e6eca 100644
--- a/ortools/flatzinc/parser_main.cc
+++ b/ortools/flatzinc/parser_main.cc
@@ -18,9 +18,8 @@
 #include <string>
 
 #include "absl/flags/flag.h"
-#include "absl/flags/parse.h"
-#include "absl/flags/usage.h"
 #include "ortools/base/commandlineflags.h"
+#include "ortools/base/init_google.h"
 #include "ortools/base/timer.h"
 #include "ortools/flatzinc/model.h"
 #include "ortools/flatzinc/parser.h"
diff --git a/ortools/linear_solver/linear_solver.proto b/ortools/linear_solver/linear_solver.proto
index 2c47324bc3..89bb49d019 100644
--- a/ortools/linear_solver/linear_solver.proto
+++ b/ortools/linear_solver/linear_solver.proto
@@ -34,6 +34,7 @@ option java_multiple_files = true;
 
 import "ortools/util/optional_boolean.proto";
 
+
 package operations_research;
 
 // A variable is always constrained in the form:
diff --git a/ortools/linear_solver/samples/stigler_diet.cc b/ortools/linear_solver/samples/stigler_diet.cc
index 52a7dd6480..22841440e1 100644
--- a/ortools/linear_solver/samples/stigler_diet.cc
+++ b/ortools/linear_solver/samples/stigler_diet.cc
@@ -20,9 +20,9 @@
 #include <vector>
 
 #include "absl/flags/flag.h"
-#include "absl/flags/parse.h"
-#include "absl/flags/usage.h"
+#include "ortools/base/init_google.h"
 #include "ortools/base/logging.h"
+#include "ortools/base/logging_flags.h"
 #include "ortools/linear_solver/linear_solver.h"
 // [END import]
 
@@ -318,8 +318,7 @@ void StiglerDiet() {
 }  // namespace operations_research
 
 int main(int argc, char** argv) {
-  google::InitGoogleLogging(argv[0]);
-  absl::ParseCommandLine(argc, argv);
+  InitGoogle(argv[0], &argc, &argv, true);
   absl::SetFlag(&FLAGS_logtostderr, true);
   operations_research::StiglerDiet();
   return EXIT_SUCCESS;
diff --git a/ortools/math_opt/cpp/matchers.h b/ortools/math_opt/cpp/matchers.h
index 1b13e11dd7..4c4d95cf21 100644
--- a/ortools/math_opt/cpp/matchers.h
+++ b/ortools/math_opt/cpp/matchers.h
@@ -91,6 +91,7 @@
 #ifndef OR_TOOLS_MATH_OPT_CPP_MATCHERS_H_
 #define OR_TOOLS_MATH_OPT_CPP_MATCHERS_H_
 
+#include <optional>
 #include <sstream>
 #include <vector>