ceres-solver/internal/ceres/codegen/expression_test.cc

// Ceres Solver - A fast non-linear least squares minimizer
// Copyright 2019 Google Inc. All rights reserved.
// http://code.google.com/p/ceres-solver/
//
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// Author: darius.rueckert@fau.de (Darius Rueckert)
//
// This file tests the Expression class. For each member function one test is
// included here.
//
#include "ceres/codegen/internal/expression.h"
#include "gtest/gtest.h"

namespace ceres {
namespace internal {

TEST(Expression, ConstructorAndAccessors) {
  Expression expr(ExpressionType::LOGICAL_NEGATION,
                  12345,
                  {1, 5, 8, 10},
                  "TestConstructor",
                  57.25);
  EXPECT_EQ(expr.type(), ExpressionType::LOGICAL_NEGATION);
  EXPECT_EQ(expr.lhs_id(), 12345);
  EXPECT_EQ(expr.arguments(), std::vector<ExpressionId>({1, 5, 8, 10}));
  EXPECT_EQ(expr.name(), "TestConstructor");
  EXPECT_EQ(expr.value(), 57.25);
}

TEST(Expression, CreateFunctions) {
  // clang-format off
  // The default constructor creates a NOP!
  EXPECT_EQ(Expression(), Expression(
            ExpressionType::NOP, kInvalidExpressionId, {}, "", 0));

  EXPECT_EQ(Expression::CreateCompileTimeConstant(72), Expression(
            ExpressionType::COMPILE_TIME_CONSTANT, kInvalidExpressionId, {}, "", 72));

  EXPECT_EQ(Expression::CreateInputAssignment("arguments[0][0]"), Expression(
            ExpressionType::INPUT_ASSIGNMENT, kInvalidExpressionId, {}, "arguments[0][0]", 0));

  EXPECT_EQ(Expression::CreateOutputAssignment(ExpressionId(5), "residuals[3]"), Expression(
            ExpressionType::OUTPUT_ASSIGNMENT, kInvalidExpressionId, {5}, "residuals[3]", 0));

  EXPECT_EQ(Expression::CreateAssignment(ExpressionId(3), ExpressionId(5)), Expression(
            ExpressionType::ASSIGNMENT, 3, {5}, "", 0));

  EXPECT_EQ(Expression::CreateBinaryArithmetic("+", ExpressionId(3),ExpressionId(5)), Expression(
            ExpressionType::BINARY_ARITHMETIC, kInvalidExpressionId, {3,5}, "+", 0));

  EXPECT_EQ(Expression::CreateUnaryArithmetic("-", ExpressionId(5)), Expression(
            ExpressionType::UNARY_ARITHMETIC, kInvalidExpressionId, {5}, "-", 0));

  EXPECT_EQ(Expression::CreateBinaryCompare("<",ExpressionId(3),ExpressionId(5)), Expression(
            ExpressionType::BINARY_COMPARISON, kInvalidExpressionId, {3,5}, "<", 0));

  EXPECT_EQ(Expression::CreateLogicalNegation(ExpressionId(5)), Expression(
            ExpressionType::LOGICAL_NEGATION, kInvalidExpressionId, {5}, "", 0));

  EXPECT_EQ(Expression::CreateFunctionCall("pow",{ExpressionId(3),ExpressionId(5)}), Expression(
            ExpressionType::FUNCTION_CALL, kInvalidExpressionId, {3,5}, "pow", 0));

  EXPECT_EQ(Expression::CreateIf(ExpressionId(5)), Expression(
            ExpressionType::IF, kInvalidExpressionId, {5}, "", 0));

  EXPECT_EQ(Expression::CreateElse(), Expression(
            ExpressionType::ELSE, kInvalidExpressionId, {}, "", 0));

  EXPECT_EQ(Expression::CreateEndIf(), Expression(
            ExpressionType::ENDIF, kInvalidExpressionId, {}, "", 0));
  // clang-format on
}

TEST(Expression, IsArithmeticExpression) {
  ASSERT_TRUE(
      Expression::CreateCompileTimeConstant(5).IsArithmeticExpression());
  ASSERT_TRUE(
      Expression::CreateFunctionCall("pow", {3, 5}).IsArithmeticExpression());
  // Logical expression are also arithmetic!
  ASSERT_TRUE(
      Expression::CreateBinaryCompare("<", 3, 5).IsArithmeticExpression());
  ASSERT_FALSE(Expression::CreateIf(5).IsArithmeticExpression());
  ASSERT_FALSE(Expression::CreateEndIf().IsArithmeticExpression());
  ASSERT_FALSE(Expression().IsArithmeticExpression());
}

TEST(Expression, IsControlExpression) {
  // In the current implementation this is the exact opposite of
  // IsArithmeticExpression.
  ASSERT_FALSE(Expression::CreateCompileTimeConstant(5).IsControlExpression());
  ASSERT_FALSE(
      Expression::CreateFunctionCall("pow", {3, 5}).IsControlExpression());
  ASSERT_FALSE(
      Expression::CreateBinaryCompare("<", 3, 5).IsControlExpression());
  ASSERT_TRUE(Expression::CreateIf(5).IsControlExpression());
  ASSERT_TRUE(Expression::CreateEndIf().IsControlExpression());
  ASSERT_TRUE(Expression().IsControlExpression());
}

TEST(Expression, IsCompileTimeConstantAndEqualTo) {
  ASSERT_TRUE(
      Expression::CreateCompileTimeConstant(5).IsCompileTimeConstantAndEqualTo(
          5));
  ASSERT_FALSE(
      Expression::CreateCompileTimeConstant(3).IsCompileTimeConstantAndEqualTo(
          5));
  ASSERT_FALSE(Expression::CreateBinaryCompare("<", 3, 5)
                   .IsCompileTimeConstantAndEqualTo(5));
}

TEST(Expression, IsReplaceableBy) {
  // Create 2 identical expression
  auto expr1 =
      Expression::CreateBinaryArithmetic("+", ExpressionId(3), ExpressionId(5));

  auto expr2 =
      Expression::CreateBinaryArithmetic("+", ExpressionId(3), ExpressionId(5));

  // They are idendical and of course replaceable
  ASSERT_EQ(expr1, expr2);
  ASSERT_EQ(expr2, expr1);
  ASSERT_TRUE(expr1.IsReplaceableBy(expr2));
  ASSERT_TRUE(expr2.IsReplaceableBy(expr1));

  // Give them different left hand sides
  expr1.set_lhs_id(72);
  expr2.set_lhs_id(42);

  // v_72 = v_3 + v_5
  // v_42 = v_3 + v_5
  // -> They should be replaceable by each other

  ASSERT_NE(expr1, expr2);
  ASSERT_NE(expr2, expr1);

  ASSERT_TRUE(expr1.IsReplaceableBy(expr2));
  ASSERT_TRUE(expr2.IsReplaceableBy(expr1));

  // A slightly differnt expression with the argument flipped
  auto expr3 =
      Expression::CreateBinaryArithmetic("+", ExpressionId(5), ExpressionId(3));

  ASSERT_NE(expr1, expr3);
  ASSERT_FALSE(expr1.IsReplaceableBy(expr3));
}

TEST(Expression, Replace) {
  auto expr1 =
      Expression::CreateBinaryArithmetic("+", ExpressionId(3), ExpressionId(5));
  expr1.set_lhs_id(13);

  auto expr2 =
      Expression::CreateAssignment(kInvalidExpressionId, ExpressionId(7));

  // We replace the arithmetic expr1 by an assignment from the variable 7. This
  // is the typical usecase in subexpression elimination.
  expr1.Replace(expr2);

  // expr1 should now be an assignment from 7 to 13
  EXPECT_EQ(expr1, Expression(ExpressionType::ASSIGNMENT, 13, {7}, "", 0));
}

TEST(Expression, DirectlyDependsOn) {
  auto expr1 =
      Expression::CreateBinaryArithmetic("+", ExpressionId(3), ExpressionId(5));

  ASSERT_TRUE(expr1.DirectlyDependsOn(ExpressionId(3)));
  ASSERT_TRUE(expr1.DirectlyDependsOn(ExpressionId(5)));
  ASSERT_FALSE(expr1.DirectlyDependsOn(ExpressionId(kInvalidExpressionId)));
  ASSERT_FALSE(expr1.DirectlyDependsOn(ExpressionId(42)));
}
TEST(Expression, MakeNop) {
  auto expr1 =
      Expression::CreateBinaryArithmetic("+", ExpressionId(3), ExpressionId(5));

  expr1.MakeNop();

  EXPECT_EQ(expr1,
            Expression(ExpressionType::NOP, kInvalidExpressionId, {}, "", 0));
}

TEST(Expression, IsSemanticallyEquivalentTo) {
  // Create 2 identical expression
  auto expr1 =
      Expression::CreateBinaryArithmetic("+", ExpressionId(3), ExpressionId(5));

  auto expr2 =
      Expression::CreateBinaryArithmetic("+", ExpressionId(3), ExpressionId(5));

  ASSERT_TRUE(expr1.IsSemanticallyEquivalentTo(expr1));
  ASSERT_TRUE(expr1.IsSemanticallyEquivalentTo(expr2));

  auto expr3 =
      Expression::CreateBinaryArithmetic("+", ExpressionId(3), ExpressionId(8));

  ASSERT_TRUE(expr1.IsSemanticallyEquivalentTo(expr3));

  auto expr4 =
      Expression::CreateBinaryArithmetic("-", ExpressionId(3), ExpressionId(5));

  ASSERT_FALSE(expr1.IsSemanticallyEquivalentTo(expr4));
}

}  // namespace internal
}  // namespace ceres