本征三元运算符中的类型错误 [英] Type error in ternary operator in Eigen
问题描述
我正在用c ++编写一门课程,以概括两个稀疏矩阵求解器(SparseLU和Sparse Cholesky)。当我尝试使用三元运算符时,它表示操作数类型不兼容,但是如果使用If语句,则代码会编译。
I'm doing a class in c++ to generalize two sparse matrix solvers (SparseLU and Sparse Cholesky). When I try to use the ternary operator it says that the operand types are incompatible, but if I use the If statement, the code compiles.
错误2错误:操作数类型不兼容( const Eigen :: Solve< Eigen :: SimplicialLDLT< Eigen :: SparseMatrix< double,0,int>,1,Eigen :: AMDOrdering< int>>,,Eigen :: Matrix< double,-1,1,0,-1,1>>和 const Eigen :: Solve< Eigen :: SparseLU< Eigen :: SparseMatrix< double,0,int>,Eigen :: COLAMDOrdering< int>>,Eigen :: Matrix< double,-1,1,0,-1,1>>)
Error 2 error: operand types are incompatible ("const Eigen::Solve < Eigen::SimplicialLDLT < Eigen::SparseMatrix < double, 0, int > , 1, Eigen::AMDOrdering < int > > , Eigen::Matrix < double, -1, 1, 0, -1, 1 > > " and "const Eigen::Solve < Eigen::SparseLU < Eigen::SparseMatrix < double, 0, int > , Eigen::COLAMDOrdering < int > > , Eigen::Matrix < double, -1, 1, 0, -1, 1 > > ")
eigen::VectorXd solve(eigen::VectorXd &b) {
return is_cholesky ? cholesky.solve(b) : lu.solve(b); // ERROR
}
X
eigen::VectorXd solve(eigen::VectorXd &b) {
if (is_cholesky) {
return cholesky.solve(b);
}
else {
return lu.solve(b);
}
}
整个代码:
#pragma once
#ifndef SOLVER_H
#define SOLVER_H
#include <Eigen/Core>
#include <Eigen/Sparse>
#include <Eigen/SparseLU>
#include <Eigen/SparseCholesky>
#define eigen Eigen
class Solver {
private:
bool is_cholesky;
eigen::SimplicialLDLT<eigen::SparseMatrix<double>> cholesky;
eigen::SparseLU<eigen::SparseMatrix<double>> lu;
public:
Solver(bool is_choleski) {
this->is_cholesky = is_choleski;
}
eigen::ComputationInfo info() {
return is_cholesky ? cholesky.info() : lu.info();
}
void compute(eigen::SparseMatrix<double> &B) {
is_cholesky ? cholesky.compute(B) : lu.compute(B);
}
eigen::VectorXd solve(eigen::VectorXd &b) {
return is_cholesky ? cholesky.solve(b) : lu.solve(b); // ERROR HERE
}
};
#endif // SOLVER_H
推荐答案
a类型的规则? b:c
表达式要求它是 b
表达式的类型还是 c $的类型c $ c>表达式。
The rules for the type of a a ? b : c
expression require that it is either the type of the b
expression or the type of the c
expression.
此处 cholesky.solve(b)
的类型不同于 lu.solve(b)
,并且两个都没有隐式转换。结果表达式将需要转换为 eigen :: VectorXd
。因此,操作数类型不兼容错误。
Here cholesky.solve(b)
has a type different to lu.solve(b)
and neither has an implicit conversion to the other. That the resulting expression will need a conversion to eigen::VectorXd
is ignored. Thus the "operand types are incompatible" error.
return is_cholesky ? cholesky.solve(b) : lu.solve(b); // ERROR
这里每个表达式都必须直接转换为 eigen: :VectorXd
(存在。)
Here each expression directly has to have a conversion to eigen::VectorXd
, which exists.
if (is_cholesky) {
return cholesky.solve(b);
}
else {
return lu.solve(b);
}
您可以强制的类型? / code>表达式到
eigen :: VectorXd
的明确提及,例如
You can force the type of the ?:
expression to eigen::VectorXd
by mentioning it explicitly, e.g.
return is_cholesky ? eigen::VectorXd{ cholesky.solve(b) } : lu.solve(b);
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