ortools-clone/ortools/sat/gate_utils_test.cc

// Copyright 2010-2025 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
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#include "ortools/sat/gate_utils.h"

#include <array>
#include <bitset>
#include <cstdint>
#include <vector>

#include "absl/random/random.h"
#include "absl/types/span.h"
#include "gtest/gtest.h"
#include "ortools/base/gmock.h"
#include "ortools/base/logging.h"
#include "ortools/sat/sat_base.h"

namespace operations_research::sat {
namespace {

TEST(CanonicalizeTruthTableTest, BasicBehavior1) {
  std::array<int, 3> key = {0, 2, 1};

  // no change here.
  SmallBitset bitmask = 0b10101010;
  CanonicalizeTruthTable<int>(absl::MakeSpan(key), bitmask);
  EXPECT_EQ(std::bitset<8>(bitmask), std::bitset<8>(0b10101010));
}

TEST(CanonicalizeTruthTableTest, BasicBehavior2) {
  std::array<int, 3> key = {2, 0, 1};
  SmallBitset bitmask = 0b10101010;
  CanonicalizeTruthTable<int>(absl::MakeSpan(key), bitmask);
  EXPECT_EQ(std::bitset<8>(bitmask), std::bitset<8>(0b11110000));
}

TEST(CanonicalizeTruthTableTest, BasicBehavior3) {
  std::array<int, 3> key = {1, 0, 2};
  SmallBitset bitmask = 0b10101010;
  CanonicalizeTruthTable<int>(absl::MakeSpan(key), bitmask);
  EXPECT_EQ(std::bitset<8>(bitmask), std::bitset<8>(0b11001100));
}

TEST(FillKeyAndBitmaskTest, BasicBehavior1) {
  std::array<BooleanVariable, 3> key;
  SmallBitset bitmask;
  FillKeyAndBitmask({Literal(+1), Literal(-2), Literal(+3)},
                    absl::MakeSpan(key), bitmask);
  EXPECT_THAT(key,
              ::testing::ElementsAre(BooleanVariable(0), BooleanVariable(1),
                                     BooleanVariable(2)));
  // The bit number 2 = 0b010 should be off.
  EXPECT_EQ(std::bitset<8>(bitmask), std::bitset<8>(0b11111011));
}

TEST(IsFunctionTest, ConstantValue) {
  EXPECT_TRUE(IsFunction(0, 3, 0b10101010));
  EXPECT_FALSE(IsFunction(1, 3, 0b10101010));
  EXPECT_FALSE(IsFunction(2, 3, 0b10101010));
}

TEST(AddHoleAtPositionTest, BasicTest) {
  EXPECT_EQ(AddHoleAtPosition(0, 0xFF), 0b111111110);
  EXPECT_EQ(AddHoleAtPosition(1, 0xFF), 0b111111101);
  EXPECT_EQ(AddHoleAtPosition(8, 0xFF), 0b011111111);
}

TEST(CanonicalizeFunctionTruthTableTest, RandomTest) {
  absl::BitGen random;
  const int num_vars = 8;

  for (int num_test = 0; num_test < 1000; ++num_test) {
    // Lets generate a random function on k random variables.
    const int k = absl::Uniform(random, 0, 4);
    const int table = absl::Uniform<uint64_t>(random, 0, 1 << (1 << k));
    const Literal output(BooleanVariable(100), absl::Bernoulli(random, 0.5));
    std::vector<Literal> inputs;
    for (int i = 0; i < k; ++i) {
      inputs.push_back(
          Literal(BooleanVariable(absl::Uniform(random, 0, num_vars)),
                  absl::Bernoulli(random, 0.5)));
    }

    LiteralIndex new_output_index = output.Index();
    std::vector<Literal> new_inputs = inputs;
    std::vector<LiteralIndex> new_inputs_index;
    for (const Literal lit : new_inputs) {
      new_inputs_index.push_back(lit.Index());
    }
    int new_table = table;
    const int new_size = CanonicalizeFunctionTruthTable(
        new_output_index, absl::MakeSpan(new_inputs_index), new_table);
    new_inputs_index.resize(new_size);
    new_inputs.clear();
    for (const LiteralIndex lit_index : new_inputs_index) {
      new_inputs.push_back(Literal(lit_index));
    }

    // Log before potential failure.
    LOG(INFO) << "IN  arity=" << k << " " << output << " = f(" << inputs << ") "
              << std::bitset<16>(table);
    LOG(INFO) << "OUT arity=" << new_size << " " << Literal(new_output_index)
              << " = f(" << new_inputs << ") " << std::bitset<16>(new_table);

    // Now check that both function always take the same value.
    for (int m = 0; m < (1 << num_vars); ++m) {
      int index = 0;
      for (int i = 0; i < inputs.size(); ++i) {
        const Literal lit = inputs[i];
        int value = (m >> lit.Variable().value()) & 1;
        if (!lit.IsPositive()) value = 1 - value;
        index |= value << i;
      }
      const int target_value = (table >> index) & 1;

      int new_index = 0;
      for (int i = 0; i < new_inputs.size(); ++i) {
        const Literal lit = new_inputs[i];
        int value = (m >> lit.Variable().value()) & 1;
        if (!lit.IsPositive()) value = 1 - value;
        new_index |= value << i;
      }
      const int new_target_value = (new_table >> new_index) & 1;

      if (output == Literal(new_output_index)) {
        ASSERT_EQ(target_value, new_target_value) << index << " " << new_index;
      } else {
        ASSERT_EQ(output, Literal(new_output_index).Negated());
        ASSERT_EQ(target_value, 1 - new_target_value)
            << index << " " << new_index;
      }
    }
  }
}

}  // namespace
}  // namespace operations_research::sat