[英]Create an Eigen sparse matrix with elements type of a struct
I would like to know if there is any way to define a sparse matrix as Eigen::SparseMatrix< StructElem >, which means each element of the matrix is an struct.我想知道是否有任何方法可以将稀疏矩阵定义为 Eigen::SparseMatrix< StructElem >,这意味着矩阵的每个元素都是一个结构。
I tried the following code, but I got the error of "no suitable constructor exists to convert from int to StructElem".我尝试了以下代码,但出现“不存在合适的构造函数来从 int 转换为 StructElem”的错误。
// the structure of element:
struct StructElem
{
unsigned int mInd;
bool mIsValid;
double mVec[ 4 ];
};
// define the matrix:
Eigen::SparseMatrix< StructElem > lA( m, n);
// work with the matrix
for( unsigned int i = 0; i < m; i++)
{
StructElem lElem;
lElem.mInd = i;
lElem.mIsValid = true;
lElem.mVec= {0.0, 0.1, 0.2, 0.4};
lA.coeffRef(i, i) = lElem; // got the error here!
}
I was wondering if you would have any sort of ideas to solve this error?我想知道您是否有解决此错误的任何想法?
You can't store classes or structs as coefficients of an Eigen::SparseMatrix
.您不能将类或结构存储为Eigen::SparseMatrix
的系数。 The constructor of the Eigen::SparseMatrix is of the type Eigen::SparseMatrix 的构造函数的类型是
Eigen::SparseMatrix< _Scalar, _Options, _StorageIndex >::SparseMatrix ( )
This means that an Eigen::SparseMatrix
can only be used to store scalar coefficients.这意味着Eigen::SparseMatrix
只能用于存储标量系数。 The scalar types that can be used are any numeric type, such as float
, double
, int
or std::complex<float>
, etc., as described here .可以使用的标量类型是任何数字类型,例如float
、 double
、 int
或std::complex<float>
等,如此处所述。
It is not clear why you would want to store anything else than a scalar type as coefficients of a SparseMatrix, since sparse matrices are used for arithmetic operations.目前尚不清楚为什么要将标量类型以外的任何内容存储为 SparseMatrix 的系数,因为稀疏矩阵用于算术运算。 But if you really want to address the structs via a SparseMatrix, you could instead prepare an array of structs of the type StructElem
and store the indices of this array into an Eigen::SparseMatrix<int>
.但是,如果您真的想通过 SparseMatrix 处理结构,则可以改为准备一个StructElem
类型的结构数组并将该数组的索引存储到Eigen::SparseMatrix<int>
中。
As @RHertel noticed, Eigen::SparseMatrix
is intended to be used for types which behave like Scalar types.正如@RHertel 所注意到的, Eigen::SparseMatrix
旨在用于行为类似于标量类型的类型。 Eg, the type should be constructable from 0
, and it should be add-able and multiply-able (the latter is only required if you do actual linear algebra with it).例如,该类型应该可以从0
构造,并且应该是可加和可乘的(只有在使用它进行实际线性代数时才需要后者)。
You can fool Eigen to handle your custom type, by adding a constructor which takes an int
(but ignores it):您可以通过添加一个采用int
的构造函数(但忽略它)来欺骗 Eigen 来处理您的自定义类型:
struct StructElem
{
unsigned int mInd;
bool mIsValid;
std::array<double,4> mVec;
explicit StructElem(int) {}
StructElem() = default;
};
Full demo: https://godbolt.org/z/7iPz5U完整演示: https://godbolt.org/z/7iPz5U
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