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ortools-clone/ortools/sat/python/linear_expr.cc

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// Copyright 2010-2024 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/python/linear_expr.h"
#include <cstdint>
#include <cstdlib>
#include <limits>
#include <string>
#include <utility>
#include <vector>
#include "absl/strings/str_cat.h"
#include "absl/strings/str_join.h"
#include "ortools/util/sorted_interval_list.h"
namespace operations_research {
namespace sat {
namespace python {
FloatLinearExpr* FloatLinearExpr::Sum(
const std::vector<FloatExprOrValue>& exprs) {
return Sum(exprs, 0.0);
}
FloatLinearExpr* FloatLinearExpr::Sum(
const std::vector<FloatExprOrValue>& exprs, double cst) {
std::vector<FloatLinearExpr*> lin_exprs;
for (const FloatExprOrValue& choice : exprs) {
if (choice.expr != nullptr) {
lin_exprs.push_back(choice.expr);
} else {
cst += choice.value;
}
}
if (lin_exprs.empty()) return new FloatConstant(cst);
if (lin_exprs.size() == 1) return Affine(lin_exprs[0], 1.0, cst);
return new FloatWeightedSum(lin_exprs, cst);
}
FloatLinearExpr* FloatLinearExpr::WeightedSum(
const std::vector<FloatExprOrValue>& exprs,
const std::vector<double>& coeffs) {
return WeightedSum(exprs, coeffs, 0.0);
}
FloatLinearExpr* FloatLinearExpr::WeightedSum(
const std::vector<FloatExprOrValue>& exprs,
const std::vector<double>& coeffs, double cst) {
std::vector<FloatLinearExpr*> lin_exprs;
std::vector<double> lin_coeffs;
for (int i = 0; i < exprs.size(); ++i) {
if (exprs[i].expr != nullptr) {
lin_exprs.push_back(exprs[i].expr);
lin_coeffs.push_back(coeffs[i]);
} else {
cst += exprs[i].value * coeffs[i];
}
}
if (lin_exprs.empty()) return new FloatConstant(cst);
if (lin_exprs.size() == 1) {
return Affine(lin_exprs[0], lin_coeffs[0], cst);
}
return new FloatWeightedSum(lin_exprs, lin_coeffs, cst);
}
FloatLinearExpr* FloatLinearExpr::Term(FloatLinearExpr* expr, double coeff) {
return new FloatAffine(expr, coeff, 0.0);
}
FloatLinearExpr* FloatLinearExpr::Affine(FloatLinearExpr* expr, double coeff,
double offset) {
return new FloatAffine(expr, coeff, offset);
}
FloatLinearExpr* FloatLinearExpr::Constant(double value) {
return new FloatConstant(value);
}
FloatLinearExpr* FloatLinearExpr::FloatAddCst(double cst) {
if (cst == 0.0) return this;
return new FloatAffine(this, 1.0, cst);
}
FloatLinearExpr* FloatLinearExpr::FloatAdd(FloatLinearExpr* other) {
std::vector<FloatLinearExpr*> exprs;
exprs.push_back(this);
exprs.push_back(other);
return new FloatWeightedSum(exprs, 0);
}
FloatLinearExpr* FloatLinearExpr::FloatSubCst(double cst) {
if (cst == 0.0) return this;
return new FloatAffine(this, 1.0, -cst);
}
FloatLinearExpr* FloatLinearExpr::FloatSub(FloatLinearExpr* other) {
std::vector<FloatLinearExpr*> exprs;
exprs.push_back(this);
exprs.push_back(other);
return new FloatWeightedSum(exprs, {1, -1}, 0);
}
FloatLinearExpr* FloatLinearExpr::FloatRSub(FloatLinearExpr* other) {
std::vector<FloatLinearExpr*> exprs;
exprs.push_back(this);
exprs.push_back(other);
return new FloatWeightedSum(exprs, {-1, 1}, 0);
}
FloatLinearExpr* FloatLinearExpr::FloatRSubCst(double cst) {
return new FloatAffine(this, -1.0, cst);
}
FloatLinearExpr* FloatLinearExpr::FloatMulCst(double cst) {
if (cst == 0.0) return Sum({});
if (cst == 1.0) return this;
return new FloatAffine(this, cst, 0.0);
}
FloatLinearExpr* FloatLinearExpr::FloatNeg() {
return new FloatAffine(this, -1.0, 0.0);
}
void FloatExprVisitor::AddToProcess(FloatLinearExpr* expr, double coeff) {
to_process_.push_back(std::make_pair(expr, coeff));
}
void FloatExprVisitor::AddConstant(double constant) { offset_ += constant; }
void FloatExprVisitor::AddVarCoeff(BaseIntVar* var, double coeff) {
canonical_terms_[var] += coeff;
}
double FloatExprVisitor::Process(FloatLinearExpr* expr,
std::vector<BaseIntVar*>* vars,
std::vector<double>* coeffs) {
AddToProcess(expr, 1.0);
while (!to_process_.empty()) {
const auto [expr, coeff] = to_process_.back();
to_process_.pop_back();
expr->VisitAsFloat(this, coeff);
}
vars->clear();
coeffs->clear();
for (const auto& [var, coeff] : canonical_terms_) {
if (coeff == 0) continue;
vars->push_back(var);
coeffs->push_back(coeff);
}
return offset_;
}
CanonicalFloatExpression::CanonicalFloatExpression(FloatLinearExpr* expr) {
FloatExprVisitor lin;
offset_ = lin.Process(expr, &vars_, &coeffs_);
}
void FloatConstant::VisitAsFloat(FloatExprVisitor* lin, double c) {
lin->AddConstant(value_ * c);
}
std::string FloatConstant::ToString() const { return absl::StrCat(value_); }
std::string FloatConstant::DebugString() const {
return absl::StrCat("FloatConstant(", value_, ")");
}
FloatWeightedSum::FloatWeightedSum(const std::vector<FloatLinearExpr*>& exprs,
double offset)
: exprs_(exprs.begin(), exprs.end()),
coeffs_(exprs.size(), 1),
offset_(offset) {}
FloatWeightedSum::FloatWeightedSum(const std::vector<FloatLinearExpr*>& exprs,
const std::vector<double>& coeffs,
double offset)
: exprs_(exprs.begin(), exprs.end()),
coeffs_(coeffs.begin(), coeffs.end()),
offset_(offset) {}
void FloatWeightedSum::VisitAsFloat(FloatExprVisitor* lin, double c) {
for (int i = 0; i < exprs_.size(); ++i) {
lin->AddToProcess(exprs_[i], coeffs_[i] * c);
}
lin->AddConstant(offset_ * c);
}
std::string FloatWeightedSum::ToString() const {
if (exprs_.empty()) {
return absl::StrCat(offset_);
}
std::string s = "(";
bool first_printed = true;
for (int i = 0; i < exprs_.size(); ++i) {
if (coeffs_[i] == 0.0) continue;
if (first_printed) {
first_printed = false;
if (coeffs_[i] == 1.0) {
absl::StrAppend(&s, exprs_[i]->ToString());
} else if (coeffs_[i] == -1.0) {
absl::StrAppend(&s, "-", exprs_[i]->ToString());
} else {
absl::StrAppend(&s, coeffs_[i], " * ", exprs_[i]->ToString());
}
} else {
if (coeffs_[i] == 1.0) {
absl::StrAppend(&s, " + ", exprs_[i]->ToString());
} else if (coeffs_[i] == -1.0) {
absl::StrAppend(&s, " - ", exprs_[i]->ToString());
} else if (coeffs_[i] > 0.0) {
absl::StrAppend(&s, " + ", coeffs_[i], " * ", exprs_[i]->ToString());
} else {
absl::StrAppend(&s, " - ", -coeffs_[i], " * ", exprs_[i]->ToString());
}
}
}
// If there are no terms, just print the offset.
if (first_printed) {
return absl::StrCat(offset_);
}
// If there is an offset, print it.
if (offset_ != 0.0) {
if (offset_ > 0.0) {
absl::StrAppend(&s, " + ", offset_);
} else {
absl::StrAppend(&s, " - ", -offset_);
}
}
absl::StrAppend(&s, ")");
return s;
}
FloatAffine::FloatAffine(FloatLinearExpr* expr, double coeff, double offset)
: expr_(expr), coeff_(coeff), offset_(offset) {}
void FloatAffine::VisitAsFloat(FloatExprVisitor* lin, double c) {
lin->AddToProcess(expr_, c * coeff_);
lin->AddConstant(offset_ * c);
}
std::string FloatAffine::ToString() const {
std::string s = "(";
if (coeff_ == 1.0) {
absl::StrAppend(&s, expr_->ToString());
} else if (coeff_ == -1.0) {
absl::StrAppend(&s, "-", expr_->ToString());
} else {
absl::StrAppend(&s, coeff_, " * ", expr_->ToString());
}
if (offset_ > 0.0) {
absl::StrAppend(&s, " + ", offset_);
} else if (offset_ < 0.0) {
absl::StrAppend(&s, " - ", -offset_);
}
absl::StrAppend(&s, ")");
return s;
}
std::string FloatAffine::DebugString() const {
return absl::StrCat("FloatAffine(expr=", expr_->DebugString(),
", coeff=", coeff_, ", offset=", offset_, ")");
}
IntLinExpr* IntLinExpr::Sum(const std::vector<IntExprOrValue>& exprs) {
return Sum(exprs, 0);
}
IntLinExpr* IntLinExpr::Sum(const std::vector<IntExprOrValue>& exprs,
int64_t cst) {
std::vector<IntLinExpr*> lin_exprs;
for (const IntExprOrValue& choice : exprs) {
if (choice.expr != nullptr) {
lin_exprs.push_back(choice.expr);
} else {
cst += choice.value;
}
}
if (lin_exprs.empty()) return new IntConstant(cst);
if (lin_exprs.size() == 1) return Affine(lin_exprs[0], 1, cst);
return new IntSum(lin_exprs, cst);
}
IntLinExpr* IntLinExpr::WeightedSum(const std::vector<IntExprOrValue>& exprs,
const std::vector<int64_t>& coeffs) {
return WeightedSum(exprs, coeffs, 0);
}
IntLinExpr* IntLinExpr::WeightedSum(const std::vector<IntExprOrValue>& exprs,
const std::vector<int64_t>& coeffs,
int64_t cst) {
std::vector<IntLinExpr*> lin_exprs;
std::vector<int64_t> lin_coeffs;
for (int i = 0; i < exprs.size(); ++i) {
if (exprs[i].expr != nullptr) {
lin_exprs.push_back(exprs[i].expr);
lin_coeffs.push_back(coeffs[i]);
} else {
cst += exprs[i].value * coeffs[i];
}
}
if (lin_exprs.empty()) return new IntConstant(cst);
if (lin_exprs.size() == 1) {
return IntLinExpr::Affine(lin_exprs[0], lin_coeffs[0], cst);
}
return new IntWeightedSum(lin_exprs, lin_coeffs, cst);
}
IntLinExpr* IntLinExpr::Term(IntLinExpr* expr, int64_t coeff) {
return Affine(expr, coeff, 0);
}
IntLinExpr* IntLinExpr::Affine(IntLinExpr* expr, int64_t coeff,
int64_t offset) {
if (coeff == 1 && offset == 0) return expr;
if (coeff == 0) return new IntConstant(offset);
return new IntAffine(expr, coeff, offset);
}
IntLinExpr* IntLinExpr::Constant(int64_t value) {
return new IntConstant(value);
}
IntLinExpr* IntLinExpr::IntAddCst(int64_t cst) {
if (cst == 0) return this;
return new IntAffine(this, 1, cst);
}
IntLinExpr* IntLinExpr::IntAdd(IntLinExpr* other) {
std::vector<IntLinExpr*> exprs;
exprs.push_back(this);
exprs.push_back(other);
return new IntSum(exprs, 0);
}
IntLinExpr* IntLinExpr::IntSubCst(int64_t cst) {
if (cst == 0) return this;
return new IntAffine(this, 1, -cst);
}
IntLinExpr* IntLinExpr::IntSub(IntLinExpr* other) {
std::vector<IntLinExpr*> exprs;
exprs.push_back(this);
exprs.push_back(other);
return new IntWeightedSum(exprs, {1, -1}, 0);
}
IntLinExpr* IntLinExpr::IntRSubCst(int64_t cst) {
return new IntAffine(this, -1, cst);
}
IntLinExpr* IntLinExpr::IntMulCst(int64_t cst) {
if (cst == 0) return new IntConstant(0);
if (cst == 1) return this;
return new IntAffine(this, cst, 0);
}
IntLinExpr* IntLinExpr::IntNeg() { return new IntAffine(this, -1, 0); }
BoundedLinearExpression* IntLinExpr::Eq(IntLinExpr* other) {
return new BoundedLinearExpression(this, other, Domain(0));
}
BoundedLinearExpression* IntLinExpr::EqCst(int64_t cst) {
return new BoundedLinearExpression(this, Domain(cst));
}
BoundedLinearExpression* IntLinExpr::Ne(IntLinExpr* other) {
return new BoundedLinearExpression(this, other, Domain(0).Complement());
}
BoundedLinearExpression* IntLinExpr::NeCst(int64_t cst) {
return new BoundedLinearExpression(this, Domain(cst).Complement());
}
BoundedLinearExpression* IntLinExpr::Le(IntLinExpr* other) {
return new BoundedLinearExpression(
this, other, Domain(std::numeric_limits<int64_t>::min(), 0));
}
BoundedLinearExpression* IntLinExpr::LeCst(int64_t cst) {
return new BoundedLinearExpression(
this, Domain(std::numeric_limits<int64_t>::min(), cst));
}
BoundedLinearExpression* IntLinExpr::Lt(IntLinExpr* other) {
return new BoundedLinearExpression(
this, other, Domain(std::numeric_limits<int64_t>::min(), -1));
}
BoundedLinearExpression* IntLinExpr::LtCst(int64_t cst) {
return new BoundedLinearExpression(
this, Domain(std::numeric_limits<int64_t>::min(), cst - 1));
}
BoundedLinearExpression* IntLinExpr::Ge(IntLinExpr* other) {
return new BoundedLinearExpression(
this, other, Domain(0, std::numeric_limits<int64_t>::max()));
}
BoundedLinearExpression* IntLinExpr::GeCst(int64_t cst) {
return new BoundedLinearExpression(
this, Domain(cst, std::numeric_limits<int64_t>::max()));
}
BoundedLinearExpression* IntLinExpr::Gt(IntLinExpr* other) {
return new BoundedLinearExpression(
this, other, Domain(1, std::numeric_limits<int64_t>::max()));
}
BoundedLinearExpression* IntLinExpr::GtCst(int64_t cst) {
return new BoundedLinearExpression(
this, Domain(cst + 1, std::numeric_limits<int64_t>::max()));
}
void IntExprVisitor::AddToProcess(IntLinExpr* expr, int64_t coeff) {
to_process_.push_back(std::make_pair(expr, coeff));
}
void IntExprVisitor::AddConstant(int64_t constant) { offset_ += constant; }
void IntExprVisitor::AddVarCoeff(BaseIntVar* var, int64_t coeff) {
canonical_terms_[var] += coeff;
}
void IntExprVisitor::ProcessAll() {
while (!to_process_.empty()) {
const auto [expr, coeff] = to_process_.back();
to_process_.pop_back();
expr->VisitAsInt(this, coeff);
}
}
int64_t IntExprVisitor::Process(std::vector<BaseIntVar*>* vars,
std::vector<int64_t>* coeffs) {
ProcessAll();
vars->clear();
coeffs->clear();
for (const auto& [var, coeff] : canonical_terms_) {
if (coeff == 0) continue;
vars->push_back(var);
coeffs->push_back(coeff);
}
return offset_;
}
int64_t IntExprVisitor::Evaluate(IntLinExpr* expr,
const CpSolverResponse& solution) {
AddToProcess(expr, 1);
ProcessAll();
int64_t value = offset_;
for (const auto& [var, coeff] : canonical_terms_) {
if (coeff == 0) continue;
value += coeff * solution.solution(var->index());
}
return value;
}
bool BaseIntVarComparator::operator()(const BaseIntVar* lhs,
const BaseIntVar* rhs) const {
return lhs->index() < rhs->index();
}
BoundedLinearExpression::BoundedLinearExpression(IntLinExpr* expr,
const Domain& bounds)
: bounds_(bounds) {
IntExprVisitor lin;
lin.AddToProcess(expr, 1);
offset_ = lin.Process(&vars_, &coeffs_);
}
BoundedLinearExpression::BoundedLinearExpression(IntLinExpr* pos,
IntLinExpr* neg,
const Domain& bounds)
: bounds_(bounds) {
IntExprVisitor lin;
lin.AddToProcess(pos, 1);
lin.AddToProcess(neg, -1);
offset_ = lin.Process(&vars_, &coeffs_);
}
BoundedLinearExpression::BoundedLinearExpression(int64_t offset,
const Domain& bounds)
: bounds_(bounds), offset_(offset) {}
const Domain& BoundedLinearExpression::bounds() const { return bounds_; }
const std::vector<BaseIntVar*>& BoundedLinearExpression::vars() const {
return vars_;
}
const std::vector<int64_t>& BoundedLinearExpression::coeffs() const {
return coeffs_;
}
int64_t BoundedLinearExpression::offset() const { return offset_; }
std::string BoundedLinearExpression::ToString() const {
std::string s;
if (vars_.empty()) {
s = absl::StrCat(offset_);
} else if (vars_.size() == 1) {
const std::string var_name = vars_[0]->ToString();
if (coeffs_[0] == 1) {
s = var_name;
} else if (coeffs_[0] == -1) {
s = absl::StrCat("-", var_name);
} else {
s = absl::StrCat(coeffs_[0], " * ", var_name);
}
if (offset_ > 0) {
absl::StrAppend(&s, " + ", offset_);
} else if (offset_ < 0) {
absl::StrAppend(&s, " - ", -offset_);
}
} else {
s = "(";
for (int i = 0; i < vars_.size(); ++i) {
const std::string var_name = vars_[i]->ToString();
if (i == 0) {
if (coeffs_[i] == 1) {
absl::StrAppend(&s, var_name);
} else if (coeffs_[i] == -1) {
absl::StrAppend(&s, "-", var_name);
} else {
absl::StrAppend(&s, coeffs_[i], " * ", var_name);
}
} else {
if (coeffs_[i] == 1) {
absl::StrAppend(&s, " + ", var_name);
} else if (coeffs_[i] == -1) {
absl::StrAppend(&s, " - ", var_name);
} else if (coeffs_[i] > 1) {
absl::StrAppend(&s, " + ", coeffs_[i], " * ", var_name);
} else {
absl::StrAppend(&s, " - ", -coeffs_[i], " * ", var_name);
}
}
}
if (offset_ > 0) {
absl::StrAppend(&s, " + ", offset_);
} else if (offset_ < 0) {
absl::StrAppend(&s, " - ", -offset_);
}
absl::StrAppend(&s, ")");
}
if (bounds_.IsFixed()) {
absl::StrAppend(&s, " == ", bounds_.Min());
} else if (bounds_.NumIntervals() == 1) {
if (bounds_.Min() == std::numeric_limits<int64_t>::min()) {
if (bounds_.Max() == std::numeric_limits<int64_t>::max()) {
return absl::StrCat("True (unbounded expr ", s, ")");
} else {
absl::StrAppend(&s, " <= ", bounds_.Max());
}
} else if (bounds_.Max() == std::numeric_limits<int64_t>::max()) {
absl::StrAppend(&s, " >= ", bounds_.Min());
} else {
return absl::StrCat(bounds_.Min(), " <= ", s, " <= ", bounds_.Max());
}
} else if (bounds_.Complement().IsFixed()) {
absl::StrAppend(&s, " != ", bounds_.Complement().Min());
} else {
absl::StrAppend(&s, " in ", bounds_.ToString());
}
return s;
}
std::string BoundedLinearExpression::DebugString() const {
return absl::StrCat("BoundedLinearExpression(vars=[",
absl::StrJoin(vars_, ", ",
[](std::string* out, BaseIntVar* var) {
absl::StrAppend(out, var->DebugString());
}),
"], coeffs=[", absl::StrJoin(coeffs_, ", "),
"], offset=", offset_, ", bounds=", bounds_.ToString(),
")");
}
bool BoundedLinearExpression::CastToBool(bool* result) const {
const bool is_zero = bounds_.IsFixed() && bounds_.FixedValue() == 0;
const Domain complement = bounds_.Complement();
const bool is_all_but_zero =
complement.IsFixed() && complement.FixedValue() == 0;
if (is_zero || is_all_but_zero) {
if (vars_.empty()) {
*result = is_zero;
return true;
} else if (vars_.size() == 2 && coeffs_[0] + coeffs_[1] == 0 &&
std::abs(coeffs_[0]) == 1) {
*result = is_all_but_zero;
return true;
}
}
return false;
}
} // namespace python
} // namespace sat
} // namespace operations_research
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