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symbolic_polynomial_test.cc
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symbolic_polynomial_test.cc
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#include <string>
#include <utility>
#include <vector>
#include <gtest/gtest.h>
#include "drake/common/symbolic.h"
#include "drake/common/test_utilities/expect_no_throw.h"
#include "drake/common/test_utilities/expect_throws_message.h"
#include "drake/common/test_utilities/symbolic_test_util.h"
namespace drake {
namespace symbolic {
namespace {
using std::pair;
using std::runtime_error;
using std::to_string;
using std::vector;
using test::ExprEqual;
using test::PolyEqual;
class SymbolicPolynomialTest : public ::testing::Test {
protected:
const Variable var_x_{"x"};
const Variable var_y_{"y"};
const Variable var_z_{"z"};
const Variables indeterminates_{var_x_, var_y_, var_z_};
const Variable var_a_{"a"};
const Variable var_b_{"b"};
const Variable var_c_{"c"};
const Variables var_xy_{var_x_, var_y_};
const Variables var_xyz_{var_x_, var_y_, var_z_};
const Variables var_abc_{var_a_, var_b_, var_c_};
const drake::VectorX<symbolic::Monomial> monomials_{
MonomialBasis(var_xyz_, 3)};
const vector<double> doubles_{-9999.0, -5.0, -1.0, 0.0, 1.0, 5.0, 9999.0};
const Expression x_{var_x_};
const Expression y_{var_y_};
const Expression z_{var_z_};
const Expression a_{var_a_};
const Expression b_{var_b_};
const Expression c_{var_c_};
const Expression xy_{var_x_ + var_y_};
const Expression xyz_{var_x_ + var_y_ + var_z_};
const vector<Expression> exprs_{
0,
-1,
3,
x_,
5 * x_,
-3 * x_,
y_,
x_* y_,
2 * x_* x_,
2 * x_* x_,
6 * x_* y_,
3 * x_* x_* y_ + 4 * pow(y_, 3) * z_ + 2,
y_*(3 * x_ * x_ + 4 * y_ * y_ * z_) + 2,
6 * pow(x_, 3) * pow(y_, 2),
2 * pow(x_, 3) * 3 * pow(y_, 2),
pow(x_, 3) - 4 * x_* y_* y_ + 2 * x_* x_* y_ - 8 * pow(y_, 3),
pow(x_ + 2 * y_, 2) * (x_ - 2 * y_),
(x_ + 2 * y_) * (x_ * x_ - 4 * y_ * y_),
(x_ * x_ + 4 * x_ * y_ + 4 * y_ * y_) * (x_ - 2 * y_),
pow(x_ + y_ + 1, 4),
pow(x_ + y_ + 1, 3),
1 + x_* x_ + 2 * (y_ - 0.5 * x_ * x_ - 0.5),
Expression(5.0) / 2.0, // constant / constant
x_ / 3.0, // var / constant
pow(x_, 2) / 2, // pow / constant
pow(x_* y_ / 3.0, 2) / 2, // pow / constant
(x_ + y_) / 2.0, // sum / constant
(x_* y_* z_ * 3) / 2.0, // product / constant
(x_* y_ / -5.0) / 2.0, // div / constant
};
};
// Tests that default constructor and EIGEN_INITIALIZE_MATRICES_BY_ZERO
// constructor both create the same value.
TEST_F(SymbolicPolynomialTest, DefaultConstructors) {
const Polynomial p;
EXPECT_TRUE(p.monomial_to_coefficient_map().empty());
const Polynomial p_zero(0);
EXPECT_TRUE(p_zero.monomial_to_coefficient_map().empty());
}
TEST_F(SymbolicPolynomialTest, ConstructFromMapType1) {
Polynomial::MapType map;
map.emplace(Monomial{var_x_}, -2.0 * a_); // x ↦ -2a
map.emplace(Monomial{{{var_y_, 3.0}}}, 4.0 * b_); // y³ ↦ 4b
const Polynomial p{map}; // p = -2ax + 4by³
EXPECT_EQ(p.monomial_to_coefficient_map(), map);
EXPECT_EQ(p.ToExpression(), -2 * a_ * x_ + 4 * b_ * pow(y_, 3));
EXPECT_EQ(p.decision_variables(), Variables({var_a_, var_b_}));
EXPECT_EQ(p.indeterminates(), Variables({var_x_, var_y_}));
}
TEST_F(SymbolicPolynomialTest, ConstructFromMapType2) {
Polynomial::MapType p_map;
for (int i = 0; i < monomials_.size(); ++i) {
p_map.emplace(monomials_[i], 1);
}
EXPECT_EQ(Polynomial{p_map}.monomial_to_coefficient_map(), p_map);
}
TEST_F(SymbolicPolynomialTest, ConstructFromMapType3) {
Polynomial::MapType map;
map.emplace(Monomial{var_x_}, -2.0 * a_); // x ↦ -2a
map.emplace(Monomial{{{var_a_, 2.0}}}, 4.0 * b_); // a² ↦ 4b
// We cannot construct a polynomial from the `map` because variable a is used
// as a decision variable (x ↦ -2a) and an indeterminate (a² ↦ 4b) at the same
// time.
if (kDrakeAssertIsArmed) {
EXPECT_THROW(Polynomial{map}, runtime_error);
}
}
TEST_F(SymbolicPolynomialTest, ConstructFromMonomial) {
for (int i = 0; i < monomials_.size(); ++i) {
const Polynomial p{monomials_[i]};
for (const std::pair<const Monomial, Expression>& map :
p.monomial_to_coefficient_map()) {
EXPECT_EQ(map.first, monomials_[i]);
EXPECT_EQ(map.second, 1);
}
}
}
TEST_F(SymbolicPolynomialTest, ConstructFromExpression) {
// Expression -------------------> Polynomial
// | .Expand() | .ToExpression()
// \/ \/
// Expanded Expression == Expression
for (const Expression& e : exprs_) {
const Expression expanded_expr{e.Expand()};
const Expression expr_from_polynomial{Polynomial{e}.ToExpression()};
EXPECT_PRED2(ExprEqual, expanded_expr, expr_from_polynomial);
}
}
TEST_F(SymbolicPolynomialTest, ConstructorFromExpressionAndIndeterminates1) {
const Polynomial p1{1.0, var_xyz_}; // p₁ = 1.0,
EXPECT_EQ(p1.monomial_to_coefficient_map(),
Polynomial::MapType({{Monomial{}, Expression(1.0)}}));
// p₂ = ax + by + cz + 10
const Polynomial p2{a_ * x_ + b_ * y_ + c_ * z_ + 10, var_xyz_};
EXPECT_EQ(p2.monomial_to_coefficient_map(),
Polynomial::MapType({{Monomial{var_x_}, a_},
{Monomial{var_y_}, b_},
{Monomial{var_z_}, c_},
{Monomial{}, 10}}));
// p₃ = 3ab²*x²y -bc*z³
const Polynomial p3{
3 * a_ * pow(b_, 2) * pow(x_, 2) * y_ - b_ * c_ * pow(z_, 3), var_xyz_};
EXPECT_EQ(p3.monomial_to_coefficient_map(),
Polynomial::MapType(
// x²y ↦ 3ab²
{{Monomial{{{var_x_, 2}, {var_y_, 1}}}, 3 * a_ * pow(b_, 2)},
// z³ ↦ -bc
{Monomial{{{var_z_, 3}}}, -b_ * c_}}));
// p₄ = 3ab²*x²y - bc*x³
const Polynomial p4{
3 * a_ * pow(b_, 2) * pow(x_, 2) * y_ - b_ * c_ * pow(x_, 3), var_xyz_};
EXPECT_EQ(p4.monomial_to_coefficient_map(),
Polynomial::MapType(
{{Monomial{{{var_x_, 2}, {var_y_, 1}}}, 3 * a_ * pow(b_, 2)},
{Monomial{{{var_x_, 3}}}, -b_ * c_}}));
}
TEST_F(SymbolicPolynomialTest, ConstructorFromExpressionAndIndeterminates2) {
const Expression e{x_ * x_ + y_ * y_}; // e = x² + y².
// Show that providing a set of indeterminates {x, y, z} which is a super-set
// of what appeared in `e`, {x, y}, doesn't change the constructed polynomial
// .
const Polynomial p1{e, {var_x_, var_y_}};
const Polynomial p2{e, {var_x_, var_y_, var_z_}};
EXPECT_EQ(p1, p2);
}
TEST_F(SymbolicPolynomialTest, IndeterminatesAndDecisionVariables) {
// p = 3ab²*x²y -bc*z³
const Polynomial p{
3 * a_ * pow(b_, 2) * pow(x_, 2) * y_ - b_ * c_ * pow(z_, 3), var_xyz_};
EXPECT_EQ(p.indeterminates(), var_xyz_);
EXPECT_EQ(p.decision_variables(), var_abc_);
}
TEST_F(SymbolicPolynomialTest, DegreeAndTotalDegree) {
// p = 3ab²*x²y -bc*z³
const Polynomial p{
3 * a_ * pow(b_, 2) * pow(x_, 2) * y_ - b_ * c_ * pow(z_, 3), var_xyz_};
EXPECT_EQ(p.Degree(var_x_), 2);
EXPECT_EQ(p.Degree(var_y_), 1);
EXPECT_EQ(p.Degree(var_z_), 3);
EXPECT_EQ(p.TotalDegree(), 3);
}
TEST_F(SymbolicPolynomialTest, AdditionPolynomialPolynomial) {
// (Polynomial(e₁) + Polynomial(e₂)).ToExpression() = (e₁ + e₂).Expand()
for (const Expression& e1 : exprs_) {
for (const Expression& e2 : exprs_) {
EXPECT_PRED2(ExprEqual, (Polynomial{e1} + Polynomial{e2}).ToExpression(),
(e1 + e2).Expand());
}
}
// Test Polynomial& operator+=(Polynomial& c);
for (const Expression& e1 : exprs_) {
for (const Expression& e2 : exprs_) {
Polynomial p{e1};
p += Polynomial{e2};
EXPECT_PRED2(ExprEqual, p.ToExpression(), (e1 + e2).Expand());
}
}
}
TEST_F(SymbolicPolynomialTest, AdditionPolynomialMonomial) {
// (Polynomial(e) + m).ToExpression() = (e + m.ToExpression()).Expand()
// (m + Polynomial(e)).ToExpression() = (m.ToExpression() + e).Expand()
for (const Expression& e : exprs_) {
const symbolic::Polynomial p{e};
for (int i = 0; i < monomials_.size(); ++i) {
const Monomial& m{monomials_[i]};
const symbolic::Polynomial sum1 = p + m;
const symbolic::Polynomial sum2 = m + p;
EXPECT_PRED2(ExprEqual, sum1.ToExpression(),
(e + m.ToExpression()).Expand());
EXPECT_PRED2(ExprEqual, sum2.ToExpression(),
(m.ToExpression() + e).Expand());
EXPECT_EQ(sum1.indeterminates(), p.indeterminates() + m.GetVariables());
EXPECT_EQ(sum2.indeterminates(), p.indeterminates() + m.GetVariables());
EXPECT_EQ(sum1.decision_variables(), p.decision_variables());
EXPECT_EQ(sum2.decision_variables(), p.decision_variables());
}
}
// Test Polynomial& operator+=(const Monomial& m);
for (const Expression& e : exprs_) {
for (int i = 0; i < monomials_.size(); ++i) {
const Monomial& m{monomials_[i]};
Polynomial p{e};
const symbolic::Variables e_indeterminates = p.indeterminates();
const symbolic::Variables e_decision_variables = p.decision_variables();
p += m;
EXPECT_PRED2(ExprEqual, p.ToExpression(),
(e + m.ToExpression()).Expand());
EXPECT_EQ(p.indeterminates(), e_indeterminates + m.GetVariables());
EXPECT_EQ(p.decision_variables(), e_decision_variables);
}
}
}
TEST_F(SymbolicPolynomialTest, AdditionPolynomialDouble) {
// (Polynomial(e) + c).ToExpression() = (e + c).Expand()
// (c + Polynomial(e)).ToExpression() = (c + e).Expand()
for (const Expression& e : exprs_) {
for (const double c : doubles_) {
EXPECT_PRED2(ExprEqual, (Polynomial(e) + c).ToExpression(),
(e + c).Expand());
EXPECT_PRED2(ExprEqual, (c + Polynomial(e)).ToExpression(),
(c + e).Expand());
}
}
// Test Polynomial& operator+=(double c).
for (const Expression& e : exprs_) {
for (const double c : doubles_) {
Polynomial p{e};
p += c;
EXPECT_PRED2(ExprEqual, p.ToExpression(), (e + c).Expand());
}
}
}
TEST_F(SymbolicPolynomialTest, AdditionMonomialMonomial) {
// (m1 + m2).ToExpression() = m1.ToExpression() + m2.ToExpression()
for (int i = 0; i < monomials_.size(); ++i) {
const Monomial& m_i{monomials_[i]};
for (int j = 0; j < monomials_.size(); ++j) {
const Monomial& m_j{monomials_[j]};
EXPECT_PRED2(ExprEqual, (m_i + m_j).ToExpression(),
m_i.ToExpression() + m_j.ToExpression());
}
}
}
TEST_F(SymbolicPolynomialTest, AdditionMonomialDouble) {
// (m + c).ToExpression() = m.ToExpression() + c
// (c + m).ToExpression() = c + m.ToExpression()
for (int i = 0; i < monomials_.size(); ++i) {
const Monomial& m{monomials_[i]};
for (const double c : doubles_) {
EXPECT_PRED2(ExprEqual, (m + c).ToExpression(), m.ToExpression() + c);
EXPECT_PRED2(ExprEqual, (c + m).ToExpression(), c + m.ToExpression());
}
}
}
TEST_F(SymbolicPolynomialTest, SubtractionPolynomialPolynomial) {
// (Polynomial(e₁) - Polynomial(e₂)).ToExpression() = (e₁ - e₂).Expand()
for (const Expression& e1 : exprs_) {
for (const Expression& e2 : exprs_) {
EXPECT_PRED2(ExprEqual, (Polynomial{e1} - Polynomial{e2}).ToExpression(),
(e1 - e2).Expand());
}
}
// Test Polynomial& operator-=(Polynomial& c);
for (const Expression& e1 : exprs_) {
for (const Expression& e2 : exprs_) {
Polynomial p{e1};
p -= Polynomial{e2};
EXPECT_PRED2(ExprEqual, p.ToExpression(), (e1 - e2).Expand());
}
}
}
TEST_F(SymbolicPolynomialTest, SubtractionPolynomialMonomial) {
// (Polynomial(e) - m).ToExpression() = (e - m.ToExpression()).Expand()
// (m - Polynomial(e)).ToExpression() = (m.ToExpression() - e).Expand()
for (const Expression& e : exprs_) {
for (int i = 0; i < monomials_.size(); ++i) {
const Monomial& m{monomials_[i]};
EXPECT_PRED2(ExprEqual, (Polynomial(e) - m).ToExpression(),
(e - m.ToExpression()).Expand());
EXPECT_PRED2(ExprEqual, (m - Polynomial(e)).ToExpression(),
(m.ToExpression() - e).Expand());
}
}
// Test Polynomial& operator-=(const Monomial& m);
for (const Expression& e : exprs_) {
for (int i = 0; i < monomials_.size(); ++i) {
const Monomial& m{monomials_[i]};
Polynomial p{e};
p -= m;
EXPECT_PRED2(ExprEqual, p.ToExpression(),
(e - m.ToExpression()).Expand());
}
}
}
TEST_F(SymbolicPolynomialTest, SubtractionPolynomialDouble) {
// (Polynomial(e) - c).ToExpression() = (e - c).Expand()
// (c - Polynomial(e)).ToExpression() = (c - e).Expand()
for (const Expression& e : exprs_) {
for (const double c : doubles_) {
EXPECT_PRED2(ExprEqual, (Polynomial(e) - c).ToExpression(),
(e - c).Expand());
EXPECT_PRED2(ExprEqual, (c - Polynomial(e)).ToExpression(),
(c - e).Expand());
}
}
// Test Polynomial& operator-=(double c).
for (const Expression& e : exprs_) {
for (const double c : doubles_) {
Polynomial p{e};
p -= c;
EXPECT_PRED2(ExprEqual, p.ToExpression(), (e - c).Expand());
}
}
}
TEST_F(SymbolicPolynomialTest, SubtractionMonomialMonomial) {
// (m1 - m2).ToExpression() = m1.ToExpression() - m2.ToExpression()
for (int i = 0; i < monomials_.size(); ++i) {
const Monomial& m_i{monomials_[i]};
for (int j = 0; j < monomials_.size(); ++j) {
const Monomial& m_j{monomials_[j]};
EXPECT_PRED2(ExprEqual, (m_i - m_j).ToExpression(),
m_i.ToExpression() - m_j.ToExpression());
}
}
}
TEST_F(SymbolicPolynomialTest, SubtractionMonomialDouble) {
// (m - c).ToExpression() = m.ToExpression() - c
// (c - m).ToExpression() = c - m.ToExpression()
for (int i = 0; i < monomials_.size(); ++i) {
const Monomial& m{monomials_[i]};
for (const double c : doubles_) {
EXPECT_PRED2(ExprEqual, (m - c).ToExpression(), m.ToExpression() - c);
EXPECT_PRED2(ExprEqual, (c - m).ToExpression(), c - m.ToExpression());
}
}
}
TEST_F(SymbolicPolynomialTest, UnaryMinus) {
// (-Polynomial(e)).ToExpression() = -(e.Expand())
for (const Expression& e : exprs_) {
EXPECT_PRED2(ExprEqual, (-Polynomial(e)).ToExpression(), -(e.Expand()));
}
}
TEST_F(SymbolicPolynomialTest, MultiplicationPolynomialPolynomial1) {
// (Polynomial(e₁) * Polynomial(e₂)).ToExpression() = (e₁ * e₂).Expand()
for (const Expression& e1 : exprs_) {
for (const Expression& e2 : exprs_) {
const symbolic::Polynomial p1{e1};
const symbolic::Polynomial p2{e2};
const symbolic::Polynomial product = p1 * p2;
EXPECT_PRED2(ExprEqual, product.ToExpression(),
(e1.Expand() * e2.Expand()).Expand());
// After multiplication, the product's indeterminates should be the union
// of p1's indeterminates and p2's indeterminates. Same for the decision
// variables.
EXPECT_EQ(product.indeterminates(),
p1.indeterminates() + p2.indeterminates());
EXPECT_EQ(product.decision_variables(),
p1.decision_variables() + p2.decision_variables());
}
}
// Test Polynomial& operator*=(Polynomial& c);
for (const Expression& e1 : exprs_) {
for (const Expression& e2 : exprs_) {
Polynomial p{e1};
const symbolic::Variables e1_indeterminates = p.indeterminates();
const symbolic::Variables e1_decision_variables = p.decision_variables();
const symbolic::Polynomial p2{e2};
p *= p2;
EXPECT_PRED2(ExprEqual, p.ToExpression(),
(e1.Expand() * e2.Expand()).Expand());
EXPECT_EQ(p.indeterminates(), e1_indeterminates + p2.indeterminates());
EXPECT_EQ(p.decision_variables(),
e1_decision_variables + p2.decision_variables());
}
}
}
TEST_F(SymbolicPolynomialTest, MultiplicationPolynomialMonomial) {
// (Polynomial(e) * m).ToExpression() = (e * m.ToExpression()).Expand()
// (m * Polynomial(e)).ToExpression() = (m.ToExpression() * e).Expand()
for (const Expression& e : exprs_) {
for (int i = 0; i < monomials_.size(); ++i) {
const Monomial& m{monomials_[i]};
const symbolic::Polynomial p{e};
const symbolic::Polynomial product1 = p * m;
const symbolic::Polynomial product2 = m * p;
EXPECT_PRED2(ExprEqual, product1.ToExpression(),
(e * m.ToExpression()).Expand());
EXPECT_PRED2(ExprEqual, product2.ToExpression(),
(m.ToExpression() * e).Expand());
EXPECT_EQ(product1.indeterminates(),
p.indeterminates() + m.GetVariables());
EXPECT_EQ(product2.indeterminates(),
p.indeterminates() + m.GetVariables());
EXPECT_EQ(product1.decision_variables(), p.decision_variables());
EXPECT_EQ(product2.decision_variables(), p.decision_variables());
}
}
// Test Polynomial& operator*=(const Monomial& m);
for (const Expression& e : exprs_) {
for (int i = 0; i < monomials_.size(); ++i) {
const Monomial& m{monomials_[i]};
Polynomial p{e};
p *= m;
EXPECT_PRED2(ExprEqual, p.ToExpression(),
(e * m.ToExpression()).Expand());
}
}
}
TEST_F(SymbolicPolynomialTest, MultiplicationPolynomialDouble) {
// (Polynomial(e) * c).ToExpression() = (e * c).Expand()
// (c * Polynomial(e)).ToExpression() = (c * e).Expand()
for (const Expression& e : exprs_) {
for (const double c : doubles_) {
EXPECT_PRED2(ExprEqual, (Polynomial(e) * c).ToExpression(),
(e * c).Expand());
EXPECT_PRED2(ExprEqual, (c * Polynomial(e)).ToExpression(),
(c * e).Expand());
}
}
// Test Polynomial& operator*=(double c).
for (const Expression& e : exprs_) {
for (const double c : doubles_) {
Polynomial p{e};
p *= c;
EXPECT_PRED2(ExprEqual, p.ToExpression(), (e * c).Expand());
}
}
}
TEST_F(SymbolicPolynomialTest, MultiplicationMonomialDouble) {
// (m * c).ToExpression() = (m.ToExpression() * c).Expand()
// (c * m).ToExpression() = (c * m.ToExpression()).Expand()
for (int i = 0; i < monomials_.size(); ++i) {
const Monomial& m{monomials_[i]};
for (const double c : doubles_) {
EXPECT_PRED2(ExprEqual, (m * c).ToExpression(),
(m.ToExpression() * c).Expand());
EXPECT_PRED2(ExprEqual, (c * m).ToExpression(),
(c * m.ToExpression()).Expand());
}
}
}
TEST_F(SymbolicPolynomialTest, MultiplicationPolynomialPolynomial2) {
// Evaluates (1 + x) * (1 - x) to confirm that the cross term 0 * x is
// erased from the product.
const Polynomial p1(1 + x_);
const Polynomial p2(1 - x_);
Polynomial::MapType product_map_expected{};
product_map_expected.emplace(Monomial(), 1);
product_map_expected.emplace(Monomial(var_x_, 2), -1);
EXPECT_EQ(product_map_expected, (p1 * p2).monomial_to_coefficient_map());
}
TEST_F(SymbolicPolynomialTest, BinaryOperationBetweenPolynomialAndVariable) {
// p = 2a²x² + 3ax + 7.
const Polynomial p{2 * pow(a_, 2) * pow(x_, 2) + 3 * a_ * x_ + 7, {var_x_}};
const Monomial m_x_cube{var_x_, 3};
const Monomial m_x_sq{var_x_, 2};
const Monomial m_x{var_x_, 1};
const Monomial m_one;
// Checks addition.
{
const Polynomial result1{p + var_a_};
const Polynomial result2{var_a_ + p};
// result1 = 2a²x² + 3ax + (7 + a).
EXPECT_TRUE(result1.EqualTo(result2));
EXPECT_EQ(result1.monomial_to_coefficient_map().size(), 3);
EXPECT_EQ(result1.indeterminates(), p.indeterminates());
EXPECT_PRED2(ExprEqual, result1.monomial_to_coefficient_map().at(m_one),
7 + a_);
const Polynomial result3{p + var_x_};
const Polynomial result4{var_x_ + p};
// result3 = 2a²x² + (3a + 1)x + 7.
EXPECT_TRUE(result3.EqualTo(result4));
EXPECT_EQ(result3.monomial_to_coefficient_map().size(), 3);
EXPECT_EQ(result3.indeterminates(), p.indeterminates());
EXPECT_PRED2(ExprEqual, result3.monomial_to_coefficient_map().at(m_x),
3 * a_ + 1);
}
// Checks subtraction.
{
const Polynomial result1{p - var_a_};
// result1 = 2a²x² + 3ax + (7 - a).
EXPECT_EQ(result1.indeterminates(), p.indeterminates());
EXPECT_EQ(result1.monomial_to_coefficient_map().size(), 3);
EXPECT_PRED2(ExprEqual, result1.monomial_to_coefficient_map().at(m_one),
7 - a_);
const Polynomial result2{var_a_ - p};
EXPECT_TRUE((-result2).EqualTo(result1));
const Polynomial result3{p - var_x_};
// result3 = 2a²x² + (3a - 1)x + 7.
EXPECT_EQ(result3.indeterminates(), p.indeterminates());
EXPECT_EQ(result3.monomial_to_coefficient_map().size(), 3);
EXPECT_PRED2(ExprEqual, result3.monomial_to_coefficient_map().at(m_x),
3 * a_ - 1);
const Polynomial result4{var_x_ - p};
EXPECT_TRUE((-result4).EqualTo(result3));
}
// Checks multiplication.
{
const Polynomial result1{p * var_a_};
// result1 = 2a³x² + 3a²x + 7a.
EXPECT_EQ(result1.indeterminates(), p.indeterminates());
EXPECT_EQ(result1.monomial_to_coefficient_map().size(), 3);
EXPECT_PRED2(ExprEqual, result1.monomial_to_coefficient_map().at(m_x_sq),
2 * pow(a_, 3));
EXPECT_PRED2(ExprEqual, result1.monomial_to_coefficient_map().at(m_x),
3 * pow(a_, 2));
EXPECT_PRED2(ExprEqual, result1.monomial_to_coefficient_map().at(m_one),
7 * a_);
const Polynomial result2{var_a_ * p};
EXPECT_TRUE(result2.EqualTo(result1));
const Polynomial result3{p * var_x_};
// result3 = 2a²x³ + 3ax² + 7x.
EXPECT_EQ(result3.indeterminates(), p.indeterminates());
EXPECT_EQ(result3.monomial_to_coefficient_map().size(), 3);
EXPECT_PRED2(ExprEqual, result3.monomial_to_coefficient_map().at(m_x_cube),
2 * pow(a_, 2));
EXPECT_PRED2(ExprEqual, result3.monomial_to_coefficient_map().at(m_x_sq),
3 * a_);
EXPECT_PRED2(ExprEqual, result3.monomial_to_coefficient_map().at(m_x), 7);
const Polynomial result4{var_x_ * p};
EXPECT_TRUE(result4.EqualTo(result3));
}
}
TEST_F(SymbolicPolynomialTest, Pow) {
for (int n = 2; n <= 5; ++n) {
for (const Expression& e : exprs_) {
Polynomial p{pow(Polynomial{e}, n)}; // p = pow(e, n)
EXPECT_PRED2(ExprEqual, p.ToExpression(), pow(e, n).Expand());
}
}
}
TEST_F(SymbolicPolynomialTest, DivideByConstant) {
for (double v = -5.5; v <= 5.5; v += 1.0) {
for (const Expression& e : exprs_) {
EXPECT_PRED2(ExprEqual, (Polynomial(e) / v).ToExpression(),
Polynomial(e / v).ToExpression());
}
}
}
TEST_F(SymbolicPolynomialTest, DifferentiateJacobian) {
// p = 2a²bx² + 3bc²x + 7ac.
const Polynomial p{
2 * pow(a_, 2) * b_ * pow(x_, 2) + 3 * b_ * pow(c_, 2) * x_ + 7 * a_ * c_,
{var_a_, var_b_, var_c_}};
// d/dx p = 4a²bx + 3bc²
const Polynomial p_x{4 * pow(a_, 2) * b_ * x_ + 3 * b_ * pow(c_, 2),
{var_a_, var_b_, var_c_}};
EXPECT_PRED2(PolyEqual, p.Differentiate(var_x_), p_x);
// d/dy p = 0
const Polynomial p_y{0, {var_a_, var_b_, var_c_}};
EXPECT_PRED2(PolyEqual, p.Differentiate(var_y_), p_y);
// d/da p = 4abx² + 7c
const Polynomial p_a{4 * a_ * b_ * pow(x_, 2) + 7 * c_,
{var_a_, var_b_, var_c_}};
EXPECT_PRED2(PolyEqual, p.Differentiate(var_a_), p_a);
// d/db p = 2a²x² + 3c²x
const Polynomial p_b{2 * pow(a_, 2) * pow(x_, 2) + 3 * pow(c_, 2) * x_,
{var_a_, var_b_, var_c_}};
EXPECT_PRED2(PolyEqual, p.Differentiate(var_b_), p_b);
// d/dc p = 6bcx + 7a
const Polynomial p_c{6 * b_ * c_ * x_ + 7 * a_, {var_a_, var_b_, var_c_}};
EXPECT_PRED2(PolyEqual, p.Differentiate(var_c_), p_c);
// Checks p.Jacobian(x, y) using static-sized matrices.
Eigen::Matrix<Variable, 2, 1> vars_xy;
vars_xy << var_x_, var_y_;
const auto J_xy = p.Jacobian(vars_xy);
static_assert(decltype(J_xy)::RowsAtCompileTime == 1 &&
decltype(J_xy)::ColsAtCompileTime == 2,
"The size of J_xy should be 1 x 2.");
EXPECT_PRED2(PolyEqual, J_xy(0, 0), p_x);
EXPECT_PRED2(PolyEqual, J_xy(0, 1), p_y);
// Checks p.Jacobian(a, b, c) using dynamic-sized matrices.
VectorX<Variable> vars_abc(3);
vars_abc << var_a_, var_b_, var_c_;
const MatrixX<Polynomial> J_abc{p.Jacobian(vars_abc)};
EXPECT_PRED2(PolyEqual, J_abc(0, 0), p_a);
EXPECT_PRED2(PolyEqual, J_abc(0, 1), p_b);
EXPECT_PRED2(PolyEqual, J_abc(0, 2), p_c);
}
TEST_F(SymbolicPolynomialTest, Integrate) {
// p = 2a²x²y + 3axy³.
const Polynomial p{2 * pow(a_, 2) * pow(x_, 2) * y_
+ 3 * a_ * x_ * pow(y_, 3),
{var_x_, var_y_}};
// ∫ p dx = 2/3 a²x³y + 3/2 ax²y³.
const Polynomial int_p_dx{
2 * pow(a_, 2) * pow(x_, 3) * y_ / 3 + 3 * a_ * pow(x_, 2) * pow(y_, 3) / 2,
{var_x_, var_y_}};
EXPECT_PRED2(PolyEqual, p.Integrate(var_x_), int_p_dx);
// ∫ p dx from 1 to 3 = 52/3 a²y + 12 ay³.
const Polynomial def_int_p_dx{
52 * pow(a_, 2) * y_ / 3 + 12 * a_ * pow(y_, 3),
{var_y_}};
EXPECT_PRED2(PolyEqual, p.Integrate(var_x_, 1, 3), def_int_p_dx);
// ∫ from [a,b] = -∫ from [b,a]
EXPECT_PRED2(PolyEqual, p.Integrate(var_x_, 3, 1), -def_int_p_dx);
// ∫ p dy = a²x²y² + 3/4 axy⁴.
const Polynomial int_p_dy{
pow(a_, 2) * pow(x_, 2) * pow(y_, 2) + 3 * a_ * x_ * pow(y_, 4) / 4,
{var_x_, var_y_}};
EXPECT_PRED2(PolyEqual, p.Integrate(var_y_), int_p_dy);
// ∫ p dz = 2a²x²yz + 3axy³z.
const Polynomial int_p_dz{
2 * pow(a_, 2) * pow(x_, 2) * y_ * z_ + 3 * a_ * x_ * pow(y_, 3) * z_,
{var_x_, var_y_, var_z_}};
EXPECT_TRUE(p.Integrate(var_z_).indeterminates().include(var_z_));
EXPECT_PRED2(PolyEqual, p.Integrate(var_z_), int_p_dz);
// ∫ p dz from -1 to 1 = 4a²x²y + 6axy³.
const Polynomial def_int_p_dz{
4 * pow(a_, 2) * pow(x_, 2) * y_ + 6 * a_ * x_ * pow(y_, 3),
{var_x_, var_y_, var_z_}};
EXPECT_TRUE(p.Integrate(var_z_).indeterminates().include(var_z_));
EXPECT_PRED2(PolyEqual, p.Integrate(var_z_, -1, 1), def_int_p_dz);
EXPECT_THROW(p.Integrate(var_a_), std::exception);
EXPECT_THROW(p.Integrate(var_a_, -1, 1), std::exception);
}
TEST_F(SymbolicPolynomialTest, ConstructNonPolynomialCoefficients) {
// Given a pair of Expression and Polynomial::MapType, `(e, map)`, we check
// `Polynomial(e, indeterminates)` has the expected map, `map`.
vector<pair<Expression, Polynomial::MapType>> testcases;
// sin(a)x = sin(a) * x
testcases.emplace_back(sin(a_) * x_,
Polynomial::MapType{{{Monomial{x_}, sin(a_)}}});
// cos(a)(x + 1)² = cos(a) * x² + 2cos(a) * x + cos(a) * 1
testcases.emplace_back(
cos(a_) * pow(x_ + 1, 2),
Polynomial::MapType{{{Monomial{{{var_x_, 2}}}, cos(a_)},
{Monomial{x_}, 2 * cos(a_)},
{Monomial{}, cos(a_)}}});
// log(a)(x + 1)² / sqrt(b)
// = log(a)/sqrt(b) * x² + 2log(a)/sqrt(b) * x + log(a)/sqrt(b) * 1
testcases.emplace_back(
log(a_) * pow(x_ + 1, 2) / sqrt(b_),
Polynomial::MapType{{{Monomial{{{var_x_, 2}}}, log(a_) / sqrt(b_)},
{Monomial{x_}, 2 * log(a_) / sqrt(b_)},
{Monomial{}, log(a_) / sqrt(b_)}}});
// (tan(a)x + 1)²
// = (tan(a))² * x² + 2tan(a) * x + 1
testcases.emplace_back(
pow(tan(a_) * x_ + 1, 2),
Polynomial::MapType{{{Monomial{{{var_x_, 2}}}, pow(tan(a_), 2)},
{Monomial{x_}, 2 * tan(a_)},
{Monomial{}, 1}}});
// abs(b + 1)x + asin(a) + acos(a) - atan(c) * x
// = (abs(b + 1) - atan(c)) * x + (asin(a) + acos(a))
testcases.emplace_back(
abs(b_ + 1) * x_ + asin(a_) + acos(a_) - atan(c_) * x_,
Polynomial::MapType{{{Monomial{x_}, abs(b_ + 1) - atan(c_)},
{Monomial{}, asin(a_) + acos(a_)}}});
// atan(b)x * atan2(a, c)y
// = (atan(b) * atan2(a, c)) * xy
testcases.emplace_back(
abs(b_) * x_ * atan2(a_, c_) * y_,
Polynomial::MapType{{{Monomial{{{var_x_, 1}, {var_y_, 1}}}, // xy
abs(b_) * atan2(a_, c_)}}});
// (sinh(a)x + cosh(b)y + tanh(c)z) / (5 * min(a, b) * max(b, c))
// = (sinh(a) / (5 * min(a, b) * max(b, c))) * x
// + (cosh(b) / (5 * min(a, b) * max(b, c))) * y
// + (tanh(c) / (5 * min(a, b) * max(b, c))) * z
testcases.emplace_back(
(sinh(a_) * x_ + cosh(b_) * y_ + tanh(c_) * z_) /
(5 * min(a_, b_) * max(b_, c_)),
Polynomial::MapType{{{
Monomial{x_},
sinh(a_) / (5 * min(a_, b_) * max(b_, c_)),
},
{
Monomial{y_},
cosh(b_) / (5 * min(a_, b_) * max(b_, c_)),
},
{
Monomial{z_},
tanh(c_) / (5 * min(a_, b_) * max(b_, c_)),
}}});
// (ceil(a) * x + floor(b) * y)²
// = pow(ceil(a), 2) * x²
// = + 2 * ceil(a) * floor(b) * xy
// = + pow(floor(a), 2) * y²
testcases.emplace_back(
pow(ceil(a_) * x_ + floor(b_) * y_, 2),
Polynomial::MapType{
{{Monomial{{{var_x_, 2}}}, ceil(a_) * ceil(a_)},
{Monomial{{{var_x_, 1}, {var_y_, 1}}}, 2 * ceil(a_) * floor(b_)},
{Monomial{{{var_y_, 2}}}, floor(b_) * floor(b_)}}});
// (ceil(a) * x + floor(b) * y)²
// = pow(ceil(a), 2) * x²
// = + 2 * ceil(a) * floor(b) * xy
// = + pow(floor(a), 2) * y²
testcases.emplace_back(
pow(ceil(a_) * x_ + floor(b_) * y_, 2),
Polynomial::MapType{
{{Monomial{{{var_x_, 2}}}, ceil(a_) * ceil(a_)},
{Monomial{{{var_x_, 1}, {var_y_, 1}}}, 2 * ceil(a_) * floor(b_)},
{Monomial{{{var_y_, 2}}}, floor(b_) * floor(b_)}}});
// UF("unnamed1", {a})) * x * UF("unnamed2", {b}) * x
// = UF("unnamed1", {a})) * UF("unnamed2", {b}) * x².
const Expression uf1{uninterpreted_function("unnamed1", {var_a_})};
const Expression uf2{uninterpreted_function("unnamed2", {var_b_})};
testcases.emplace_back(
uf1 * x_ * uf2 * x_,
Polynomial::MapType{{{Monomial{{{var_x_, 2}}}, uf1 * uf2}}});
// (x + y)² = x² + 2xy + y²
testcases.emplace_back(pow(x_ + y_, 2),
Polynomial::MapType{{
{Monomial{{{var_x_, 2}}}, 1},
{Monomial{{{var_x_, 1}, {var_y_, 1}}}, 2},
{Monomial{{{var_y_, 2}}}, 1},
}});
// pow(pow(x, 2.5), 2) = x⁵
testcases.emplace_back(pow(pow(x_, 2.5), 2),
Polynomial::MapType{{{Monomial{{{var_x_, 5}}}, 1}}});
// pow(pow(x * y, 2.5), 2) = (xy)⁵
testcases.emplace_back(
pow(pow(x_ * y_, 2.5), 2),
Polynomial::MapType{{{Monomial{{{var_x_, 5}, {var_y_, 5}}}, 1}}});
for (const pair<Expression, Polynomial::MapType>& item : testcases) {
const Expression& e{item.first};
const Polynomial p{e, indeterminates_};
const Polynomial::MapType& expected_map{item.second};
EXPECT_EQ(p.monomial_to_coefficient_map(), expected_map);
}
}
TEST_F(SymbolicPolynomialTest, NegativeTestConstruction1) {
// sin(a) * x is a polynomial.
const Expression e1{sin(a_) * x_};
DRAKE_EXPECT_NO_THROW(Polynomial(e1, indeterminates_));
// sin(x) * x is a not polynomial.
const Expression e2{sin(x_) * x_};
EXPECT_THROW(Polynomial(e2, indeterminates_), runtime_error);
}
TEST_F(SymbolicPolynomialTest, NegativeTestConstruction2) {
// aˣ x is not a polynomial.
const Expression e{pow(a_, x_)};
EXPECT_THROW(Polynomial(e, indeterminates_), runtime_error);
}
TEST_F(SymbolicPolynomialTest, NegativeTestConstruction3) {
// x⁻¹ is not a polynomial.
const Expression e{pow(x_, -1)};
EXPECT_THROW(Polynomial(e, indeterminates_), runtime_error);
}
TEST_F(SymbolicPolynomialTest, NegativeTestConstruction4) {
// x^(2.5) is not a polynomial.
const Expression e{pow(x_, 2.5)};
EXPECT_THROW(Polynomial(e, indeterminates_), runtime_error);
}
TEST_F(SymbolicPolynomialTest, NegativeTestConstruction5) {
// xˣ is not a polynomial.
const Expression e{pow(x_, x_)};
EXPECT_THROW(Polynomial(e, indeterminates_), runtime_error);
}
TEST_F(SymbolicPolynomialTest, NegativeTestConstruction6) {
// 1 / a is polynomial.
const Expression e1{1 / a_};
DRAKE_EXPECT_NO_THROW(Polynomial(e1, indeterminates_));
// However, 1 / x is not a polynomial.
const Expression e2{1 / x_};
EXPECT_THROW(Polynomial(e2, indeterminates_), runtime_error);
}
TEST_F(SymbolicPolynomialTest, NegativeTestConstruction7) {
// sin(x + a) is not a polynomial.
const Expression e{sin(x_ + a_)};
EXPECT_THROW(Polynomial(e, indeterminates_), runtime_error);
}
TEST_F(SymbolicPolynomialTest, Evaluate) {
// p = ax²y + bxy + cz
const Polynomial p{a_ * x_ * x_ * y_ + b_ * x_ * y_ + c_ * z_, var_xyz_};
const Environment env1{{
{var_a_, 1.0},
{var_b_, 2.0},
{var_c_, 3.0},
{var_x_, -1.0},
{var_y_, -2.0},
{var_z_, -3.0},
}};
const double expected1{1.0 * -1.0 * -1.0 * -2.0 + 2.0 * -1.0 * -2.0 +
3.0 * -3.0};
EXPECT_EQ(p.Evaluate(env1), expected1);
const Environment env2{{
{var_a_, 4.0},
{var_b_, 1.0},
{var_c_, 2.0},
{var_x_, -7.0},
{var_y_, -5.0},
{var_z_, -2.0},
}};
const double expected2{4.0 * -7.0 * -7.0 * -5.0 + 1.0 * -7.0 * -5.0 +
2.0 * -2.0};
EXPECT_EQ(p.Evaluate(env2), expected2);
const Environment partial_env{{
{var_a_, 4.0},
{var_c_, 2.0},
{var_x_, -7.0},
{var_z_, -2.0},
}};
EXPECT_THROW(p.Evaluate(partial_env), runtime_error);
}
TEST_F(SymbolicPolynomialTest, PartialEvaluate1) {
// p1 = a*x² + b*x + c
// p2 = p1[x ↦ 3.0] = 3²a + 3b + c.
const Polynomial p1{a_ * x_ * x_ + b_ * x_ + c_, var_xyz_};
const Polynomial p2{a_ * 3.0 * 3.0 + b_ * 3.0 + c_, var_xyz_};
const Environment env{{{var_x_, 3.0}}};
EXPECT_PRED2(PolyEqual, p1.EvaluatePartial(env), p2);
EXPECT_PRED2(PolyEqual, p1.EvaluatePartial(var_x_, 3.0), p2);
}
TEST_F(SymbolicPolynomialTest, PartialEvaluate2) {
// p1 = a*xy² - a*xy + c
// p2 = p1[y ↦ 2.0] = (4a - 2a)*x + c = 2ax + c
const Polynomial p1{a_ * x_ * y_ * y_ - a_ * x_ * y_ + c_, var_xyz_};
const Polynomial p2{2 * a_ * x_ + c_, var_xyz_};
const Environment env{{{var_y_, 2.0}}};
EXPECT_PRED2(PolyEqual, p1.EvaluatePartial(env), p2);
EXPECT_PRED2(PolyEqual, p1.EvaluatePartial(var_y_, 2.0), p2);
}
TEST_F(SymbolicPolynomialTest, PartialEvaluate3) {
// p1 = a*x² + b*x + c
// p2 = p1[a ↦ 2.0, x ↦ 3.0] = 2*3² + 3b + c
// = 18 + 3b + c
const Polynomial p1{a_ * x_ * x_ + b_ * x_ + c_, var_xyz_};
const Polynomial p2{18 + 3 * b_ + c_, var_xyz_};
const Environment env{{{var_a_, 2.0}, {var_x_, 3.0}}};
EXPECT_PRED2(PolyEqual, p1.EvaluatePartial(env), p2);
}
TEST_F(SymbolicPolynomialTest, PartialEvaluate4) {
// p = (a + c / b + c)*x² + b*x + c
//
// Partially evaluating p with [a ↦ 0, b ↦ 0, c ↦ 0] throws `runtime_error`
// because of the divide-by-zero
const Polynomial p{((a_ + c_) / (b_ + c_)) * x_ * x_ + b_ * x_ + c_,
var_xyz_};
const Environment env{{{var_a_, 0.0}, {var_b_, 0.0}, {var_c_, 0.0}}};
EXPECT_THROW(p.EvaluatePartial(env), runtime_error);
}
TEST_F(SymbolicPolynomialTest, EvaluateIndeterminates) {
const Polynomial p(var_x_ * var_x_ + 5 * var_x_ * var_y_);
// We intentionally test the case that `indeterminates` being a strict
// superset of p.indeterminates().
Vector3<symbolic::Variable> indeterminates(var_x_, var_z_, var_y_);
Eigen::Matrix<double, 3, 4> indeterminates_values;
// clang-format off
indeterminates_values << 1, 2, 3, 4,
-1, -2, -3, -4,
2, 3, 4, 5;
// clang-format on
Eigen::VectorXd polynomial_values =
p.EvaluateIndeterminates(indeterminates, indeterminates_values);
ASSERT_EQ(polynomial_values.rows(), indeterminates_values.cols());
for (int i = 0; i < indeterminates_values.cols(); ++i) {
symbolic::Environment env;
env.insert(indeterminates, indeterminates_values.col(i));
EXPECT_EQ(polynomial_values(i), p.Evaluate(env));
}
// The exception case, when the polynomial coefficients are not all constant;
const Polynomial p_exception(var_x_ * var_x_ * var_a_, var_xyz_);
DRAKE_EXPECT_THROWS_MESSAGE(
p_exception.EvaluateIndeterminates(indeterminates, indeterminates_values),
".* the coefficient .* is not a constant");
}
TEST_F(SymbolicPolynomialTest, Hash) {
const auto h = std::hash<Polynomial>{};
Polynomial p1{x_ * x_};
const Polynomial p2{x_ * x_};
EXPECT_EQ(p1, p2);
EXPECT_EQ(h(p1), h(p2));
p1 += Polynomial{y_};
EXPECT_NE(p1, p2);
EXPECT_NE(h(p1), h(p2));
}
TEST_F(SymbolicPolynomialTest, CoefficientsAlmostEqual) {
Polynomial p1{x_ * x_};
// Two polynomials with the same number of terms.
EXPECT_TRUE(p1.CoefficientsAlmostEqual(Polynomial{x_ * x_}, 1e-6));
EXPECT_TRUE(
p1.CoefficientsAlmostEqual(Polynomial{(1 + 1e-7) * x_ * x_}, 1e-6));
EXPECT_FALSE(p1.CoefficientsAlmostEqual(Polynomial{2 * x_ * x_}, 1e-6));
// Another polynomial with an additional small constant term.