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Standard library header <linalg> (C++26)

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Standard library headers
 

This header is part of the numeric library.

Contents

Classes

Defined in namespace std::linalg
std::mdspan layout mapping policy that represents a square matrix that stores only the entries in one triangle, in a packed contiguous format
(class template)[edit]
std::mdspan accessor policy whose reference represents the product of a scaling factor that is fixed and its nested std::mdspan accessor's reference
(class template)[edit]
std::mdspan accessor policy whose reference represents the complex conjugate of its nested std::mdspan accessor's reference
(class template)[edit]
std::mdspan layout mapping policy that swaps the rightmost two indices, extents, and strides of any unique layout mapping policy
(class template)[edit]

Tags

Defined in namespace std::linalg
describe the order of elements in an std::mdspan with linalg::layout_blas_packed layout
(tag)[edit]
specify whether algorithms and other users of a matrix should access the upper triangle or lower triangle of the matrix
(tag)[edit]
specify whether algorithms should access diagonal entries of the matrix
(tag)[edit]

Functions

Defined in namespace std::linalg
In-place transformations
(C++26)
returns a new read-only std::mdspan computed by the elementwise product of the scaling factor and the corresponding elements of the given std::mdspan
(function template)[edit]
(C++26)
returns a new read-only std::mdspan whose elements are the complex conjugates of the corresponding elements of the given std::mdspan
(function template)[edit]
(C++26)
returns a new std::mdspan representing the transpose of the input matrix by the given std::mdspan
(function template)[edit]
returns a conjugate transpose view of an object
(function template)[edit]
BLAS 1 functions
generates plane rotation
(function template)[edit]
applies plane rotation to vectors
(function template)[edit]
swaps all corresponding elements of matrix or vector
(function template)[edit]
(C++26)
overwrites matrix or vector with the result of computing the elementwise multiplication by a scalar
(function template)[edit]
(C++26)
copies elements of one matrix or vector into another
(function template)[edit]
(C++26)
adds vectors or matrices elementwise
(function template)[edit]
(C++26)
returns nonconjugated dot product of two vectors
(function template)[edit]
(C++26)
returns conjugated dot product of two vectors
(function template)[edit]
returns scaled sum of squares of the vector elements
(function template)[edit]
returns Euclidean norm of a vector
(function template)[edit]
returns sum of absolute values of the vector elements
(function template)[edit]
returns index of maximum absolute value of vector elements
(function template)[edit]
returns Frobenius norm of a matrix
(function template)[edit]
returns one norm of a matrix
(function template)[edit]
returns infinity norm of a matrix
(function template)[edit]
BLAS 2 functions
computes matrix-vector product
(function template)[edit]
computes symmetric matrix-vector product
(function template)[edit]
computes Hermitian matrix-vector product
(function template)[edit]
computes triangular matrix-vector product
(function template)[edit]
solves a triangular linear system
(function template)[edit]
performs nonsymmetric nonconjugated rank-1 update of a matrix
(function template)[edit]
performs nonsymmetric conjugated rank-1 update of a matrix
(function template)[edit]
performs rank-1 update of a symmetric matrix
(function template)[edit]
performs rank-1 update of a Hermitian matrix
(function template)[edit]
performs rank-2 update of a symmetric matrix
(function template)[edit]
performs rank-2 update of a Hermitian matrix
(function template)[edit]
BLAS 3 functions
computes matrix-matrix product
(function template)[edit]
computes symmetric matrix-matrix product
(function template)[edit]
computes Hermitian matrix-matrix product
(function template)[edit]
computes triangular matrix-matrix product
(function template)[edit]
performs rank-k update of a symmetric matrix
(function template)[edit]
performs rank-k update of a Hermitian matrix
(function template)[edit]
performs rank-2k update of a symmetric matrix
(function template)[edit]
performs rank-2k update of a Hermitian matrix
(function template)[edit]
solves multiple triangular linear systems
(function template)[edit]

[edit]Synopsis

namespace std::linalg{   // storage order tagsstruct column_major_t;inlineconstexpr column_major_t column_major;struct row_major_t;inlineconstexpr row_major_t row_major;   // triangle tagsstruct upper_triangle_t;inlineconstexpr upper_triangle_t upper_triangle;struct lower_triangle_t;inlineconstexpr lower_triangle_t lower_triangle;   // diagonal tagsstruct implicit_unit_diagonal_t;inlineconstexpr implicit_unit_diagonal_t implicit_unit_diagonal;struct explicit_diagonal_t;inlineconstexpr explicit_diagonal_t explicit_diagonal;   // class template layout_blas_packedtemplate<class Triangle, class StorageOrder>class layout_blas_packed;   // exposition-only concepts and traitstemplate<class T>struct __is_mdspan;// exposition only   template<class T> concept __in_vector =/* see description */;// exposition only   template<class T> concept __out_vector =/* see description */;// exposition only   template<class T> concept __inout_vector =/* see description */;// exposition only   template<class T> concept __in_matrix =/* see description */;// exposition only   template<class T> concept __out_matrix =/* see description */;// exposition only   template<class T> concept __inout_matrix =/* see description */;// exposition only   template<class T> concept __possibly_packed_inout_matrix =/* see description */;// exposition only   template<class T> concept __in_object =/* see description */;// exposition only   template<class T> concept __out_object =/* see description */;// exposition only   template<class T> concept __inout_object =/* see description */;// exposition only   // scaled in-place transformationtemplate<class ScalingFactor, class Accessor>class scaled_accessor;   template<class ScalingFactor, class ElementType, class Extents, class Layout, class Accessor>constexprauto scaled(ScalingFactor scaling_factor, mdspan<ElementType, Extents, Layout, Accessor> x);   // conjugated in-place transformationtemplate<class Accessor>class conjugated_accessor;   template<class ElementType, class Extents, class Layout, class Accessor>constexprauto conjugated(mdspan<ElementType, Extents, Layout, Accessor> a);   // transposed in-place transformationtemplate<class Layout>class layout_transpose;   template<class ElementType, class Extents, class Layout, class Accessor>constexprauto transposed(mdspan<ElementType, Extents, Layout, Accessor> a);   // conjugated transposed in-place transformationtemplate<class ElementType, class Extents, class Layout, class Accessor>constexprauto conjugate_transposed(mdspan<ElementType, Extents, Layout, Accessor> a);   // algorithms// compute Givens rotation   template<class Real>struct setup_givens_rotation_result { Real c; Real s; Real r;};   template<class Real>struct setup_givens_rotation_result<complex<Real>>{ Real c; complex<Real> s; complex<Real> r;};   template<class Real> setup_givens_rotation_result<Real> setup_givens_rotation(Real a, Real b)noexcept;   template<class Real> setup_givens_rotation_result<complex<Real>> setup_givens_rotation(complex<Real> a, complex<Real> b)noexcept;   // apply computed Givens rotationtemplate<__inout_vector InOutVec1, __inout_vector InOutVec2, class Real>void apply_givens_rotation(InOutVec1 x, InOutVec2 y, Real c, Real s);   template<class ExecutionPolicy, __inout_vector InOutVec1, __inout_vector InOutVec2, class Real>void apply_givens_rotation(ExecutionPolicy&& exec, InOutVec1 x, InOutVec2 y, Real c, Real s);   template<__inout_vector InOutVec1, __inout_vector InOutVec2, class Real>void apply_givens_rotation(InOutVec1 x, InOutVec2 y, Real c, complex<Real> s);   template<class ExecutionPolicy, __inout_vector InOutVec1, __inout_vector InOutVec2, class Real>void apply_givens_rotation(ExecutionPolicy&& exec, InOutVec1 x, InOutVec2 y, Real c, complex<Real> s);   // swap elementstemplate<__inout_object InOutObj1, __inout_object InOutObj2>void swap_elements(InOutObj1 x, InOutObj2 y);   template<class ExecutionPolicy, __inout_object InOutObj1, __inout_object InOutObj2>void swap_elements(ExecutionPolicy&& exec, InOutObj1 x, InOutObj2 y);   // multiply elements by scalartemplate<class Scalar, __inout_object InOutObj>void scale(Scalar alpha, InOutObj x);   template<class ExecutionPolicy, class Scalar, __inout_object InOutObj>void scale(ExecutionPolicy&& exec, Scalar alpha, InOutObj x);   // copy elementstemplate<__in_object InObj, __out_object OutObj>void copy(InObj x, OutObj y);   template<class ExecutionPolicy, __in_object InObj, __out_object OutObj>void copy(ExecutionPolicy&& exec, InObj x, OutObj y);   // add elementwisetemplate<__in_object InObj1, __in_object InObj2, __out_object OutObj>void add(InObj1 x, InObj2 y, OutObj z);   template<class ExecutionPolicy, __in_object InObj1, __in_object InObj2, __out_object OutObj>void add(ExecutionPolicy&& exec, InObj1 x, InObj2 y, OutObj z);   // nonconjugated dot product of two vectorstemplate<__in_vector InVec1, __in_vector InVec2, class Scalar> Scalar dot(InVec1 v1, InVec2 v2, Scalar init);   template<class ExecutionPolicy, __in_vector InVec1, __in_vector InVec2, class Scalar> Scalar dot(ExecutionPolicy&& exec, InVec1 v1, InVec2 v2, Scalar init);   template<__in_vector InVec1, __in_vector InVec2>auto dot(InVec1 v1, InVec2 v2)->/* see description */;   template<class ExecutionPolicy, __in_vector InVec1, __in_vector InVec2>auto dot(ExecutionPolicy&& exec, InVec1 v1, InVec2 v2)->/* see description */;   // conjugated dot product of two vectorstemplate<__in_vector InVec1, __in_vector InVec2, class Scalar> Scalar dotc(InVec1 v1, InVec2 v2, Scalar init);   template<class ExecutionPolicy, __in_vector InVec1, __in_vector InVec2, class Scalar> Scalar dotc(ExecutionPolicy&& exec, InVec1 v1, InVec2 v2, Scalar init);   template<__in_vector InVec1, __in_vector InVec2>auto dotc(InVec1 v1, InVec2 v2)->/* see description */;   template<class ExecutionPolicy, __in_vector InVec1, __in_vector InVec2>auto dotc(ExecutionPolicy&& exec, InVec1 v1, InVec2 v2)->/* see description */;   // Scaled sum of squares of a vector's elementstemplate<class Scalar>struct sum_of_squares_result { Scalar scaling_factor; Scalar scaled_sum_of_squares;};   template<__in_vector InVec, class Scalar> sum_of_squares_result<Scalar> vector_sum_of_squares(InVec v, sum_of_squares_result<Scalar> init);   template<class ExecutionPolicy, __in_vector InVec, class Scalar> sum_of_squares_result<Scalar> vector_sum_of_squares(ExecutionPolicy&& exec, InVec v, sum_of_squares_result<Scalar> init);   // Euclidean norm of a vectortemplate<__in_vector InVec, class Scalar> Scalar vector_two_norm(InVec v, Scalar init);   template<class ExecutionPolicy, __in_vector InVec, class Scalar> Scalar vector_two_norm(ExecutionPolicy&& exec, InVec v, Scalar init);   template<__in_vector InVec>auto vector_two_norm(InVec v)->/* see description */;   template<class ExecutionPolicy, __in_vector InVec>auto vector_two_norm(ExecutionPolicy&& exec, InVec v)->/* see description */;   // sum of absolute values of vector elementstemplate<__in_vector InVec, class Scalar> Scalar vector_abs_sum(InVec v, Scalar init);template<class ExecutionPolicy, __in_vector InVec, class Scalar> Scalar vector_abs_sum(ExecutionPolicy&& exec, InVec v, Scalar init);   template<__in_vector InVec>auto vector_abs_sum(InVec v)->/* see description */;   template<class ExecutionPolicy, __in_vector InVec>auto vector_abs_sum(ExecutionPolicy&& exec, InVec v)->/* see description */;   // index of maximum absolute value of vector elementstemplate<__in_vector InVec>typename InVec::extents_type vector_idx_abs_max(InVec v);   template<class ExecutionPolicy, __in_vector InVec>typename InVec::extents_type vector_idx_abs_max(ExecutionPolicy&& exec, InVec v);   // Frobenius norm of a matrixtemplate<__in_matrix InMat, class Scalar> Scalar matrix_frob_norm(InMat A, Scalar init);   template<class ExecutionPolicy, __in_matrix InMat, class Scalar> Scalar matrix_frob_norm(ExecutionPolicy&& exec, InMat A, Scalar init);   template<__in_matrix InMat>auto matrix_frob_norm(InMat A)->/* see description */;   template<class ExecutionPolicy, __in_matrix InMat>auto matrix_frob_norm(ExecutionPolicy&& exec, InMat A)->/* see description */;   // One norm of a matrixtemplate<__in_matrix InMat, class Scalar> Scalar matrix_one_norm(InMat A, Scalar init);   template<class ExecutionPolicy, __in_matrix InMat, class Scalar> Scalar matrix_one_norm(ExecutionPolicy&& exec, InMat A, Scalar init);   template<__in_matrix InMat>auto matrix_one_norm(InMat A)->/* see description */;   template<class ExecutionPolicy, __in_matrix InMat>auto matrix_one_norm(ExecutionPolicy&& exec, InMat A)->/* see description */;   // Infinity norm of a matrixtemplate<__in_matrix InMat, class Scalar> Scalar matrix_inf_norm(InMat A, Scalar init);   template<class ExecutionPolicy, __in_matrix InMat, class Scalar> Scalar matrix_inf_norm(ExecutionPolicy&& exec, InMat A, Scalar init);   template<__in_matrix InMat>auto matrix_inf_norm(InMat A)->/* see description */;   template<class ExecutionPolicy, __in_matrix InMat>auto matrix_inf_norm(ExecutionPolicy&& exec, InMat A)->/* see description */;   // general matrix-vector producttemplate<__in_matrix InMat, __in_vector InVec, __out_vector OutVec>void matrix_vector_product(InMat A, InVec x, OutVec y);   template<class ExecutionPolicy, __in_matrix InMat, __in_vector InVec, __out_vector OutVec>void matrix_vector_product(ExecutionPolicy&& exec, InMat A, InVec x, OutVec y);   template<__in_matrix InMat, __in_vector InVec1, __in_vector InVec2, __out_vector OutVec>void matrix_vector_product(InMat A, InVec1 x, InVec2 y, OutVec z);   template<class ExecutionPolicy, __in_matrix InMat, __in_vector InVec1, __in_vector InVec2, __out_vector OutVec>void matrix_vector_product(ExecutionPolicy&& exec, InMat A, InVec1 x, InVec2 y, OutVec z);   // symmetric matrix-vector producttemplate<__in_matrix InMat, class Triangle, __in_vector InVec, __out_vector OutVec>void symmetric_matrix_vector_product(InMat A, Triangle t, InVec x, OutVec y);   template<class ExecutionPolicy, __in_matrix InMat, class Triangle, __in_vector InVec, __out_vector OutVec>void symmetric_matrix_vector_product(ExecutionPolicy&& exec, InMat A, Triangle t, InVec x, OutVec y);   template<__in_matrix InMat, class Triangle, __in_vector InVec1, __in_vector InVec2, __out_vector OutVec>void symmetric_matrix_vector_product(InMat A, Triangle t, InVec1 x, InVec2 y, OutVec z);   template<class ExecutionPolicy, __in_matrix InMat, class Triangle, __in_vector InVec1, __in_vector InVec2, __out_vector OutVec>void symmetric_matrix_vector_product(ExecutionPolicy&& exec, InMat A, Triangle t, InVec1 x, InVec2 y, OutVec z);   // Hermitian matrix-vector producttemplate<__in_matrix InMat, class Triangle, __in_vector InVec, __out_vector OutVec>void hermitian_matrix_vector_product(InMat A, Triangle t, InVec x, OutVec y);   template<class ExecutionPolicy, __in_matrix InMat, class Triangle, __in_vector InVec, __out_vector OutVec>void hermitian_matrix_vector_product(ExecutionPolicy&& exec, InMat A, Triangle t, InVec x, OutVec y);   template<__in_matrix InMat, class Triangle, __in_vector InVec1, __in_vector InVec2, __out_vector OutVec>void hermitian_matrix_vector_product(InMat A, Triangle t, InVec1 x, InVec2 y, OutVec z);   template<class ExecutionPolicy, __in_matrix InMat, class Triangle, __in_vector InVec1, __in_vector InVec2, __out_vector OutVec>void hermitian_matrix_vector_product(ExecutionPolicy&& exec, InMat A, Triangle t, InVec1 x, InVec2 y, OutVec z);   // Triangular matrix-vector product// Overwriting triangular matrix-vector producttemplate<__in_matrix InMat, class Triangle, class DiagonalStorage, __in_vector InVec, __out_vector OutVec>void triangular_matrix_vector_product(InMat A, Triangle t, DiagonalStorage d, InVec x, OutVec y);   template<class ExecutionPolicy, __in_matrix InMat, class Triangle, class DiagonalStorage, __in_vector InVec, __out_vector OutVec>void triangular_matrix_vector_product(ExecutionPolicy&& exec, InMat A, Triangle t, DiagonalStorage d, InVec x, OutVec y);   // In-place triangular matrix-vector producttemplate<__in_matrix InMat, class Triangle, class DiagonalStorage, __inout_vector InOutVec>void triangular_matrix_vector_product(InMat A, Triangle t, DiagonalStorage d, InOutVec y);   template<class ExecutionPolicy, __in_matrix InMat, class Triangle, class DiagonalStorage, __inout_vector InOutVec>void triangular_matrix_vector_product(ExecutionPolicy&& exec, InMat A, Triangle t, DiagonalStorage d, InOutVec y);   // Updating triangular matrix-vector producttemplate<__in_matrix InMat, class Triangle, class DiagonalStorage, __in_vector InVec1, __in_vector InVec2, __out_vector OutVec>void triangular_matrix_vector_product(InMat A, Triangle t, DiagonalStorage d, InVec1 x, InVec2 y, OutVec z);   template<class ExecutionPolicy, __in_matrix InMat, class Triangle, class DiagonalStorage, __in_vector InVec1, __in_vector InVec2, __out_vector OutVec>void triangular_matrix_vector_product(ExecutionPolicy&& exec, InMat A, Triangle t, DiagonalStorage d, InVec1 x, InVec2 y, OutVec z);   // Solve a triangular linear system, not in placetemplate<__in_matrix InMat, class Triangle, class DiagonalStorage, __in_vector InVec, __out_vector OutVec, class BinaryDivideOp>void triangular_matrix_vector_solve(InMat A, Triangle t, DiagonalStorage d, InVec b, OutVec x, BinaryDivideOp divide);   template<class ExecutionPolicy, __in_matrix InMat, class Triangle, class DiagonalStorage, __in_vector InVec, __out_vector OutVec, class BinaryDivideOp>void triangular_matrix_vector_solve(ExecutionPolicy&& exec, InMat A, Triangle t, DiagonalStorage d, InVec b, OutVec x, BinaryDivideOp divide);   template<__in_matrix InMat, class Triangle, class DiagonalStorage, __in_vector InVec, __out_vector OutVec>void triangular_matrix_vector_solve(InMat A, Triangle t, DiagonalStorage d, InVec b, OutVec x);   template<class ExecutionPolicy, __in_matrix InMat, class Triangle, class DiagonalStorage, __in_vector InVec, __out_vector OutVec>void triangular_matrix_vector_solve(ExecutionPolicy&& exec, InMat A, Triangle t, DiagonalStorage d, InVec b, OutVec x);   // Solve a triangular linear system, in placetemplate<__in_matrix InMat, class Triangle, class DiagonalStorage, __inout_vector InOutVec, class BinaryDivideOp>void triangular_matrix_vector_solve(InMat A, Triangle t, DiagonalStorage d, InOutVec b, BinaryDivideOp divide);   template<class ExecutionPolicy, __in_matrix InMat, class Triangle, class DiagonalStorage, __inout_vector InOutVec, class BinaryDivideOp>void triangular_matrix_vector_solve(ExecutionPolicy&& exec, InMat A, Triangle t, DiagonalStorage d, InOutVec b, BinaryDivideOp divide);   template<__in_matrix InMat, class Triangle, class DiagonalStorage, __inout_vector InOutVec>void triangular_matrix_vector_solve(InMat A, Triangle t, DiagonalStorage d, InOutVec b);   template<class ExecutionPolicy, __in_matrix InMat, class Triangle, class DiagonalStorage, __inout_vector InOutVec>void triangular_matrix_vector_solve(ExecutionPolicy&& exec, InMat A, Triangle t, DiagonalStorage d, InOutVec b);   // nonconjugated rank-1 matrix updatetemplate<__in_vector InVec1, __in_vector InVec2, __inout_matrix InOutMat>void matrix_rank_1_update(InVec1 x, InVec2 y, InOutMat A);   template<class ExecutionPolicy, __in_vector InVec1, __in_vector InVec2, __inout_matrix InOutMat>void matrix_rank_1_update(ExecutionPolicy&& exec, InVec1 x, InVec2 y, InOutMat A);   // conjugated rank-1 matrix updatetemplate<__in_vector InVec1, __in_vector InVec2, __inout_matrix InOutMat>void matrix_rank_1_update_c(InVec1 x, InVec2 y, InOutMat A);   template<class ExecutionPolicy, __in_vector InVec1, __in_vector InVec2, __inout_matrix InOutMat>void matrix_rank_1_update_c(ExecutionPolicy&& exec, InVec1 x, InVec2 y, InOutMat A);   // symmetric rank-1 matrix updatetemplate<__in_vector InVec, __possibly_packed_inout_matrix InOutMat, class Triangle>void symmetric_matrix_rank_1_update(InVec x, InOutMat A, Triangle t);   template<class ExecutionPolicy, __in_vector InVec, __possibly_packed_inout_matrix InOutMat, class Triangle>void symmetric_matrix_rank_1_update(ExecutionPolicy&& exec, InVec x, InOutMat A, Triangle t);   template<class Scalar, __in_vector InVec, __possibly_packed_inout_matrix InOutMat, class Triangle>void symmetric_matrix_rank_1_update(Scalar alpha, InVec x, InOutMat A, Triangle t);   template<class ExecutionPolicy, class Scalar, __in_vector InVec, __possibly_packed_inout_matrix InOutMat, class Triangle>void symmetric_matrix_rank_1_update(ExecutionPolicy&& exec, Scalar alpha, InVec x, InOutMat A, Triangle t);   // Hermitian rank-1 matrix updatetemplate<__in_vector InVec, __possibly_packed_inout_matrix InOutMat, class Triangle>void hermitian_matrix_rank_1_update(InVec x, InOutMat A, Triangle t);   template<class ExecutionPolicy, __in_vector InVec, __possibly_packed_inout_matrix InOutMat, class Triangle>void hermitian_matrix_rank_1_update(ExecutionPolicy&& exec, InVec x, InOutMat A, Triangle t);   template<class Scalar, __in_vector InVec, __possibly_packed_inout_matrix InOutMat, class Triangle>void hermitian_matrix_rank_1_update(Scalar alpha, InVec x, InOutMat A, Triangle t);   template<class ExecutionPolicy, class Scalar, __in_vector InVec, __possibly_packed_inout_matrix InOutMat, class Triangle>void hermitian_matrix_rank_1_update(ExecutionPolicy&& exec, Scalar alpha, InVec x, InOutMat A, Triangle t);   // symmetric rank-2 matrix updatetemplate<__in_vector InVec1, __in_vector InVec2, __possibly_packed_inout_matrix InOutMat, class Triangle>void symmetric_matrix_rank_2_update(InVec1 x, InVec2 y, InOutMat A, Triangle t);   template<class ExecutionPolicy, __in_vector InVec1, __in_vector InVec2, __possibly_packed_inout_matrix InOutMat, class Triangle>void symmetric_matrix_rank_2_update(ExecutionPolicy&& exec, InVec1 x, InVec2 y, InOutMat A, Triangle t);   // Hermitian rank-2 matrix updatetemplate<__in_vector InVec1, __in_vector InVec2, __possibly_packed_inout_matrix InOutMat, class Triangle>void hermitian_matrix_rank_2_update(InVec1 x, InVec2 y, InOutMat A, Triangle t);   template<class ExecutionPolicy, __in_vector InVec1, __in_vector InVec2, __possibly_packed_inout_matrix InOutMat, class Triangle>void hermitian_matrix_rank_2_update(ExecutionPolicy&& exec, InVec1 x, InVec2 y, InOutMat A, Triangle t);   // general matrix-matrix producttemplate<__in_matrix InMat1, __in_matrix InMat2, __out_matrix OutMat>void matrix_product(InMat1 A, InMat2 B, OutMat C);   template<class ExecutionPolicy, __in_matrix InMat1, __in_matrix InMat2, __out_matrix OutMat>void matrix_product(ExecutionPolicy&& exec, InMat1 A, InMat2 B, OutMat C);   template<__in_matrix InMat1, __in_matrix InMat2, __in_matrix InMat3, __out_matrix OutMat>void matrix_product(InMat1 A, InMat2 B, InMat3 E, OutMat C);   template<class ExecutionPolicy, __in_matrix InMat1, __in_matrix InMat2, __in_matrix InMat3, __out_matrix OutMat>void matrix_product(ExecutionPolicy&& exec, InMat1 A, InMat2 B, InMat3 E, OutMat C);     // symmetric matrix-matrix product// overwriting symmetric matrix-matrix left producttemplate<__in_matrix InMat1, class Triangle, __in_matrix InMat2, __out_matrix OutMat>void symmetric_matrix_product(InMat1 A, Triangle t, InMat2 B, OutMat C);   template<class ExecutionPolicy, __in_matrix InMat1, class Triangle, __in_matrix InMat2, __out_matrix OutMat>void symmetric_matrix_product(ExecutionPolicy&& exec, InMat1 A, Triangle t, InMat2 B, OutMat C);   // overwriting symmetric matrix-matrix right producttemplate<__in_matrix InMat1, __in_matrix InMat2, class Triangle, __out_matrix OutMat>void symmetric_matrix_product(InMat1 B, InMat2 A, Triangle t, OutMat C);   template<class ExecutionPolicy, __in_matrix InMat1, __in_matrix InMat2, class Triangle, __out_matrix OutMat>void symmetric_matrix_product(ExecutionPolicy&& exec, InMat1 B, InMat2 A, Triangle t, OutMat C);   // updating symmetric matrix-matrix left producttemplate<__in_matrix InMat1, class Triangle, __in_matrix InMat2, __in_matrix InMat3, __out_matrix OutMat>void symmetric_matrix_product(InMat1 A, Triangle t, InMat2 B, InMat3 E, OutMat C);   template<class ExecutionPolicy, __in_matrix InMat1, class Triangle, __in_matrix InMat2, __in_matrix InMat3, __out_matrix OutMat>void symmetric_matrix_product(ExecutionPolicy&& exec, InMat1 A, Triangle t, InMat2 B, InMat3 E, OutMat C);   // updating symmetric matrix-matrix right producttemplate<__in_matrix InMat1, __in_matrix InMat2, class Triangle, __in_matrix InMat3, __out_matrix OutMat>void symmetric_matrix_product(InMat1 B, InMat2 A, Triangle t, InMat3 E, OutMat C);   template<class ExecutionPolicy, __in_matrix InMat1, __in_matrix InMat2, class Triangle, __in_matrix InMat3, __out_matrix OutMat>void symmetric_matrix_product(ExecutionPolicy&& exec, InMat1 B, InMat2 A, Triangle t, InMat3 E, OutMat C);   // Hermitian matrix-matrix product// overwriting Hermitian matrix-matrix left producttemplate<__in_matrix InMat1, class Triangle, __in_matrix InMat2, __out_matrix OutMat>void hermitian_matrix_product(InMat1 A, Triangle t, InMat2 B, OutMat C);template<class ExecutionPolicy, __in_matrix InMat1, class Triangle, __in_matrix InMat2, __out_matrix OutMat>void hermitian_matrix_product(ExecutionPolicy&& exec, InMat1 A, Triangle t, InMat2 B, OutMat C);   // overwriting Hermitian matrix-matrix right producttemplate<__in_matrix InMat1, __in_matrix InMat2, class Triangle, __out_matrix OutMat>void hermitian_matrix_product(InMat1 B, InMat2 A, Triangle t, OutMat C);   template<class ExecutionPolicy, __in_matrix InMat1, __in_matrix InMat2, class Triangle, __out_matrix OutMat>void hermitian_matrix_product(ExecutionPolicy&& exec, InMat1 B, InMat2 A, Triangle t, OutMat C);   // updating Hermitian matrix-matrix left producttemplate<__in_matrix InMat1, class Triangle, __in_matrix InMat2, __in_matrix InMat3, __out_matrix OutMat>void hermitian_matrix_product(InMat1 A, Triangle t, InMat2 B, InMat3 E, OutMat C);   template<class ExecutionPolicy, __in_matrix InMat1, class Triangle, __in_matrix InMat2, __in_matrix InMat3, __out_matrix OutMat>void hermitian_matrix_product(ExecutionPolicy&& exec, InMat1 A, Triangle t, InMat2 B, InMat3 E, OutMat C);   // updating Hermitian matrix-matrix right producttemplate<__in_matrix InMat1, __in_matrix InMat2, class Triangle, __in_matrix InMat3, __out_matrix OutMat>void hermitian_matrix_product(InMat1 B, InMat2 A, Triangle t, InMat3 E, OutMat C);   template<class ExecutionPolicy, __in_matrix InMat1, __in_matrix InMat2, class Triangle, __in_matrix InMat3, __out_matrix OutMat>void hermitian_matrix_product(ExecutionPolicy&& exec, InMat1 B, InMat2 A, Triangle t, InMat3 E, OutMat C);   // triangular matrix-matrix product// overwriting triangular matrix-matrix left producttemplate<__in_matrix InMat1, class Triangle, class DiagonalStorage, __in_matrix InMat2, __out_matrix OutMat>void triangular_matrix_product(InMat1 A, Triangle t, DiagonalStorage d, InMat2 B, OutMat C);   template<class ExecutionPolicy, __in_matrix InMat1, class Triangle, class DiagonalStorage, __in_matrix InMat2, __out_matrix OutMat>void triangular_matrix_product(ExecutionPolicy&& exec, InMat1 A, Triangle t, DiagonalStorage d, InMat2 B, OutMat C);   template<__in_matrix InMat1, class Triangle, class DiagonalStorage, __inout_matrix InOutMat>void triangular_matrix_left_product(InMat1 A, Triangle t, DiagonalStorage d, InOutMat C);   template<class ExecutionPolicy, __in_matrix InMat1, class Triangle, class DiagonalStorage, __inout_matrix InOutMat>void triangular_matrix_left_product(ExecutionPolicy&& exec, InMat1 A, Triangle t, DiagonalStorage d, InOutMat C);   // overwriting triangular matrix-matrix right producttemplate<__in_matrix InMat1, __in_matrix InMat2, class Triangle, class DiagonalStorage, __out_matrix OutMat>void triangular_matrix_product(InMat1 B, InMat2 A, Triangle t, DiagonalStorage d, OutMat C);   template<class ExecutionPolicy, __in_matrix InMat1, __in_matrix InMat2, class Triangle, class DiagonalStorage, __out_matrix OutMat>void triangular_matrix_product(ExecutionPolicy&& exec, InMat1 B, InMat2 A, Triangle t, DiagonalStorage d, OutMat C);   template<__in_matrix InMat1, class Triangle, class DiagonalStorage, __inout_matrix InOutMat>void triangular_matrix_right_product(InMat1 A, Triangle t, DiagonalStorage d, InOutMat C);   template<class ExecutionPolicy, __in_matrix InMat1, class Triangle, class DiagonalStorage, __inout_matrix InOutMat>void triangular_matrix_right_product(ExecutionPolicy&& exec, InMat1 A, Triangle t, DiagonalStorage d, InOutMat C);   // updating triangular matrix-matrix left producttemplate<__in_matrix InMat1, class Triangle, class DiagonalStorage, __in_matrix InMat2, __in_matrix InMat3, __out_matrix OutMat>void triangular_matrix_product(InMat1 A, Triangle t, DiagonalStorage d, InMat2 B, InMat3 E, OutMat C);   template<class ExecutionPolicy, __in_matrix InMat1, class Triangle, class DiagonalStorage, __in_matrix InMat2, __in_matrix InMat3, __out_matrix OutMat>void triangular_matrix_product(ExecutionPolicy&& exec, InMat1 A, Triangle t, DiagonalStorage d, InMat2 B, InMat3 E, OutMat C);   // updating triangular matrix-matrix right producttemplate<__in_matrix InMat1, __in_matrix InMat2, class Triangle, class DiagonalStorage, __in_matrix InMat3, __out_matrix OutMat>void triangular_matrix_product(InMat1 B, InMat2 A, Triangle t, DiagonalStorage d, InMat3 E, OutMat C);   template<class ExecutionPolicy, __in_matrix InMat1, __in_matrix InMat2, class Triangle, class DiagonalStorage, __in_matrix InMat3, __out_matrix OutMat>void triangular_matrix_product(ExecutionPolicy&& exec, InMat1 B, InMat2 A, Triangle t, DiagonalStorage d, InMat3 E, OutMat C);   // rank-k symmetric matrix updatetemplate<class Scalar, __in_matrix InMat1, __possibly_packed_inout_matrix InOutMat, class Triangle>void symmetric_matrix_rank_k_update(Scalar alpha, InMat1 A, InOutMat C, Triangle t);   template<class Scalar, class ExecutionPolicy, ___in_matrix InMat1, __possibly_packed_inout_matrix InOutMat, class Triangle>void symmetric_matrix_rank_k_update(ExecutionPolicy&& exec, Scalar alpha, InMat1 A, InOutMat C, Triangle t);   template<__in_matrix InMat1, __possibly_packed_inout_matrix InOutMat, class Triangle>void symmetric_matrix_rank_k_update(InMat1 A, InOutMat C, Triangle t);   template<class ExecutionPolicy, __in_matrix InMat1, __possibly_packed_inout_matrix InOutMat, class Triangle>void symmetric_matrix_rank_k_update(ExecutionPolicy&& exec, InMat1 A, InOutMat C, Triangle t);   // rank-k Hermitian matrix updatetemplate<class Scalar, __in_matrix InMat1, __possibly_packed_inout_matrix InOutMat, class Triangle>void hermitian_matrix_rank_k_update(Scalar alpha, InMat1 A, InOutMat C, Triangle t);   template<class ExecutionPolicy, class Scalar, __in_matrix InMat1, __possibly_packed_inout_matrix InOutMat, class Triangle void hermitian_matrix_rank_k_update(ExecutionPolicy&& exec, Scalar alpha, InMat1 A, InOutMat C, Triangle t);   template<__in_matrix InMat1, __possibly_packed_inout_matrix InOutMat, class Triangle>void hermitian_matrix_rank_k_update(InMat1 A, InOutMat C, Triangle t);   template<class ExecutionPolicy, __in_matrix InMat1, __possibly_packed_inout_matrix InOutMat, class Triangle>void hermitian_matrix_rank_k_update(ExecutionPolicy&& exec, InMat1 A, InOutMat C, Triangle t);   // rank-2k symmetric matrix updatetemplate<__in_matrix InMat1, __in_matrix InMat2, __possibly_packed_inout_matrix InOutMat, class Triangle>void symmetric_matrix_rank_2k_update(InMat1 A, InMat2 B, InOutMat C, Triangle t);   template<class ExecutionPolicy, __in_matrix InMat1, __in_matrix InMat2, __possibly_packed_inout_matrix InOutMat, class Triangle>void symmetric_matrix_rank_2k_update(ExecutionPolicy&& exec, InMat1 A, InMat2 B, InOutMat C, Triangle t);   // rank-2k Hermitian matrix updatetemplate<__in_matrix InMat1, __in_matrix InMat2, __possibly_packed_inout_matrix InOutMat, class Triangle>void hermitian_matrix_rank_2k_update(InMat1 A, InMat2 B, InOutMat C, Triangle t);   template<class ExecutionPolicy, __in_matrix InMat1, __in_matrix InMat2, __possibly_packed_inout_matrix InOutMat, class Triangle>void hermitian_matrix_rank_2k_update(ExecutionPolicy&& exec, InMat1 A, InMat2 B, InOutMat C, Triangle t);   // solve multiple triangular linear systems// with triangular matrix on the lefttemplate<__in_matrix InMat1, class Triangle, class DiagonalStorage, __in_matrix InMat2, __out_matrix OutMat, class BinaryDivideOp>void triangular_matrix_matrix_left_solve(InMat1 A, Triangle t, DiagonalStorage d, InMat2 B, OutMat X, BinaryDivideOp divide);   template<class ExecutionPolicy, __in_matrix InMat1, class Triangle, class DiagonalStorage, __in_matrix InMat2, __out_matrix OutMat, class BinaryDivideOp>void triangular_matrix_matrix_left_solve(ExecutionPolicy&& exec, InMat1 A, Triangle t, DiagonalStorage d, InMat2 B, OutMat X, BinaryDivideOp divide);   template<__in_matrix InMat1, class Triangle, class DiagonalStorage, __inout_matrix InOutMat, class BinaryDivideOp>void triangular_matrix_matrix_left_solve(InMat1 A, Triangle t, DiagonalStorage d, InOutMat B, BinaryDivideOp divide);   template<class ExecutionPolicy, __in_matrix InMat1, class Triangle, class DiagonalStorage, __inout_matrix InOutMat, class BinaryDivideOp>void triangular_matrix_matrix_left_solve(ExecutionPolicy&& exec, InMat1 A, Triangle t, DiagonalStorage d, InOutMat B, BinaryDivideOp divide);   template<__in_matrix InMat1, class Triangle, class DiagonalStorage, __in_matrix InMat2, __out_matrix OutMat>void triangular_matrix_matrix_left_solve(InMat1 A, Triangle t, DiagonalStorage d, InMat2 B, OutMat X);   template<class ExecutionPolicy, __in_matrix InMat1, class Triangle, class DiagonalStorage, __in_matrix InMat2, __out_matrix OutMat>void triangular_matrix_matrix_left_solve(ExecutionPolicy&& exec, InMat1 A, Triangle t, DiagonalStorage d, InMat2 B, OutMat X);   template<__in_matrix InMat1, class Triangle, class DiagonalStorage, __inout_matrix InOutMat>void triangular_matrix_matrix_left_solve(InMat1 A, Triangle t, DiagonalStorage d, InOutMat B);   template<class ExecutionPolicy, __in_matrix InMat1, class Triangle, class DiagonalStorage, __inout_matrix InOutMat>void triangular_matrix_matrix_left_solve(ExecutionPolicy&& exec, InMat1 A, Triangle t, DiagonalStorage d, InOutMat B);   // solve multiple triangular linear systems// with triangular matrix on the righttemplate<__in_matrix InMat1, class Triangle, class DiagonalStorage, __in_matrix InMat2, __out_matrix OutMat, class BinaryDivideOp>void triangular_matrix_matrix_right_solve(InMat1 A, Triangle t, DiagonalStorage d, InMat2 B, OutMat X, BinaryDivideOp divide);   template<class ExecutionPolicy, __in_matrix InMat1, class Triangle, class DiagonalStorage, __in_matrix InMat2, __out_matrix OutMat, class BinaryDivideOp>void triangular_matrix_matrix_right_solve(ExecutionPolicy&& exec, InMat1 A, Triangle t, DiagonalStorage d, InMat2 B, OutMat X, BinaryDivideOp divide);   template<__in_matrix InMat1, class Triangle, class DiagonalStorage, __inout_matrix InOutMat, class BinaryDivideOp>void triangular_matrix_matrix_right_solve(InMat1 A, Triangle t, DiagonalStorage d, InOutMat B, BinaryDivideOp divide);   template<class ExecutionPolicy, __in_matrix InMat1, class Triangle, class DiagonalStorage, __inout_matrix InOutMat, class BinaryDivideOp>void triangular_matrix_matrix_right_solve(ExecutionPolicy&& exec, InMat1 A, Triangle t, DiagonalStorage d, InOutMat B, BinaryDivideOp divide));   template<__in_matrix InMat1, class Triangle, class DiagonalStorage, __in_matrix InMat2, __out_matrix OutMat>void triangular_matrix_matrix_right_solve(InMat1 A, Triangle t, DiagonalStorage d, InMat2 B, OutMat X);   template<class ExecutionPolicy, __in_matrix InMat1, class Triangle, class DiagonalStorage, __in_matrix InMat2, __out_matrix OutMat>void triangular_matrix_matrix_right_solve(ExecutionPolicy&& exec, InMat1 A, Triangle t, DiagonalStorage d, InMat2 B, OutMat X);   template<__in_matrix InMat1, class Triangle, class DiagonalStorage, __inout_matrix InOutMat>void triangular_matrix_matrix_right_solve(InMat1 A, Triangle t, DiagonalStorage d, InOutMat B);   template<class ExecutionPolicy, __in_matrix InMat1, class Triangle, class DiagonalStorage, __inout_matrix InOutMat>void triangular_matrix_matrix_right_solve(ExecutionPolicy&& exec, InMat1 A, Triangle t, DiagonalStorage d, InOutMat B);}

[edit]Tags

namespace std::linalg{struct column_major_t {explicit column_major_t()=default;};inlineconstexpr column_major_t column_major ={};   struct row_major_t {explicit row_major_t()=default;};inlineconstexpr row_major_t row_major ={};   struct upper_triangle_t {explicit upper_triangle_t()=default;};inlineconstexpr upper_triangle_t upper_triangle ={};   struct lower_triangle_t {explicit lower_triangle_t()=default;};inlineconstexpr lower_triangle_t lower_triangle ={};   struct implicit_unit_diagonal_t {explicit implicit_unit_diagonal_t()=default;};inlineconstexpr implicit_unit_diagonal_t implicit_unit_diagonal ={};   struct explicit_diagonal_t {explicit explicit_diagonal_t()=default;};inlineconstexpr explicit_diagonal_t explicit_diagonal ={};}

[edit]Class template std::linalg::layout_blas_packed

namespace std::linalg{template<class Triangle, class StorageOrder>class layout_blas_packed {public:using triangle_type = Triangle;using storage_order_type = StorageOrder;   template<class Extents>struct mapping {public:using extents_type = Extents;using index_type =typename extents_type::index_type;using size_type =typename extents_type::size_type;using rank_type =typename extents_type::rank_type;using layout_type = layout_blas_packed<Triangle, StorageOrder>;   private: Extents __the_extents{};// exposition only   public:constexpr mapping()noexcept=default;constexpr mapping(const mapping&)noexcept=default;constexpr mapping(const extents_type& e)noexcept;template<class OtherExtents>constexprexplicit(!is_convertible_v<OtherExtents, extents_type>) mapping(const mapping<OtherExtents>& other)noexcept;   constexpr mapping& operator=(const mapping&)noexcept=default;   constexpr extents_type extents()constnoexcept{return __the_extents;}   constexpr size_type required_span_size()constnoexcept;   template<class Index0, class Index1>constexpr index_type operator()(Index0 ind0, Index1 ind1)constnoexcept;   staticconstexprbool is_always_unique(){return(extents_type::static_extent(0)!= dynamic_extent && extents_type::static_extent(0)<2)||(extents_type::static_extent(1)!= dynamic_extent && extents_type::static_extent(1)<2);}staticconstexprbool is_always_exhaustive(){returntrue;}staticconstexprbool is_always_strided(){return is_always_unique();}   constexprbool is_unique()constnoexcept{return __the_extents.extent(0)<2;}constexprbool is_exhaustive()constnoexcept{returntrue;}constexprbool is_strided()constnoexcept{return __the_extents.extent(0)<2;}   constexpr index_type stride(rank_type)constnoexcept;   template<class OtherExtents>friendconstexprbool operator==(const mapping&, const mapping<OtherExtents>&)noexcept;   };};}

[edit]Class template std::linalg::scaled_accessor

namespace std::linalg{template<class ScalingFactor, class NestedAccessor>class scaled_accessor {public:using element_type = add_const_t<decltype(declval<ScalingFactor>()* declval<NestedAccessor::element_type>())>;using reference = remove_const_t<element_type>;using data_handle_type = NestedAccessor::data_handle_type;using offset_policy = scaled_accessor<ScalingFactor, NestedAccessor::offset_policy>;   constexpr scaled_accessor()=default;template<class OtherNestedAccessor>explicit(!is_convertible_v<OtherNestedAccessor, NestedAccessor>)constexpr scaled_accessor(const scaled_accessor<ScalingFactor, OtherNestedAccessor>&);constexpr scaled_accessor(const ScalingFactor& s, const Accessor& a);   constexpr reference access(data_handle_type p, size_t i)constnoexcept;constexpr offset_policy::data_handle_type offset(data_handle_type p, size_t i)constnoexcept;   constexprconst ScalingFactor& scaling_factor()constnoexcept{return __scaling_factor;}constexprconst NestedAccessor& nested_accessor()constnoexcept{return __nested_accessor;}   private: ScalingFactor __scaling_factor;// exposition only NestedAccessor __nested_accessor;// exposition only};}

[edit]Class template std::linalg::conjugated_accessor

namespace std::linalg{template<class NestedAccessor>class conjugated_accessor {private: NestedAccessor __nested_accessor;// exposition only   public:using element_type = add_const_t<decltype(/*conj-if-needed*/(declval<NestedAccessor::element_type>()))>;using reference = remove_const_t<element_type>;using data_handle_type =typename NestedAccessor::data_handle_type;using offset_policy = conjugated_accessor<NestedAccessor::offset_policy>;   constexpr conjugated_accessor()=default;template<class OtherNestedAccessor>explicit(!is_convertible_v<OtherNestedAccessor, NestedAccessor>)constexpr conjugated_accessor(const conjugated_accessor<OtherNestedAccessor>& other);   constexpr reference access(data_handle_type p, size_t i)const;   constexprtypename offset_policy::data_handle_type offset(data_handle_type p, size_t i)const;   constexprconst NestedAccessor& nested_accessor()constnoexcept{return __nested_accessor;}};}

[edit]Class template std::linalg::layout_transpose

namespace std::linalg{template<class InputExtents>using __transpose_extents_t =/* see description */;// exposition only   template<class Layout>class layout_transpose {public:using nested_layout_type = Layout;   template<class Extents>struct mapping {private:using __nested_mapping_type =typename Layout::template mapping< __transpose_extents_t<Extents>>;// exposition only   __nested_mapping_type __nested_mapping;// exposition only extents_type __extents;// exposition only   public:using extents_type = Extents;using index_type =typename extents_type::index_type;using size_type =typename extents_type::size_type;using rank_type =typename extents_type::rank_type;using layout_type = layout_transpose;   constexprexplicit mapping(const __nested_mapping_type& map);   constexprconst extents_type& extents()constnoexcept{return __extents;}   constexpr index_type required_span_size()const{return __nested_mapping.required_span_size();}   template<class Index0, class Index1>constexpr index_type operator()(Index0 ind0, Index1 ind1)const{return __nested_mapping(ind1, ind0);}   constexprconst __nested_mapping_type& nested_mapping()constnoexcept{return __nested_mapping;}   staticconstexprbool is_always_unique()noexcept{return __nested_mapping_type::is_always_unique();}staticconstexprbool is_always_exhaustive()noexcept{return __nested_mapping_type::is_always_exhaustive();}staticconstexprbool is_always_strided()noexcept{return __nested_mapping_type::is_always_strided();}   constexprbool is_unique()const{return __nested_mapping.is_unique();}constexprbool is_exhaustive()const{return __nested_mapping.is_exhaustive();}constexprbool is_strided()const{return __nested_mapping.is_strided();}   constexpr index_type stride(size_t r)const;   template<class OtherExtents>friendconstexprbool operator==(const mapping& x, const mapping<OtherExtents>& y);};};}

[edit]Helper concepts and traits

namespace std::linalg{template<class T>struct __is_mdspan : false_type {};// exposition only   template<class ElementType, class Extents, class Layout, class Accessor>struct __is_mdspan<mdspan<ElementType, Extents, Layout, Accessor>>: true_type {};// exposition only   template<class T> concept __in_vector =// exposition only __is_mdspan<T>::value&& T::rank()==1;   template<class T> concept __out_vector =// exposition only __is_mdspan<T>::value&& T::rank()==1&& is_assignable_v<typename T::reference, typename T::element_type>&& T::is_always_unique();   template<class T> concept __inout_vector =// exposition only __is_mdspan<T>::value&& T::rank()==1&& is_assignable_v<typename T::reference, typename T::element_type>&& T::is_always_unique();   template<class T> concept __in_matrix =// exposition only __is_mdspan<T>::value&& T::rank()==2;   template<class T> concept __out_matrix =// exposition only __is_mdspan<T>::value&& T::rank()==2&& is_assignable_v<typename T::reference, typename T::element_type>&& T::is_always_unique();   template<class T> concept __inout_matrix =// exposition only __is_mdspan<T>::value&& T::rank()==2&& is_assignable_v<typename T::reference, typename T::element_type>&& T::is_always_unique();   template<class T> concept __possibly_packed_inout_matrix =// exposition only __is_mdspan<T>::value&& T::rank()==2&& is_assignable_v<typename T::reference, typename T::element_type>&&(T::is_always_unique()|| is_same_v<typename T::layout_type, layout_blas_packed>);   template<class T> concept __in_object =// exposition only __is_mdspan<T>::value&&(T::rank()==1|| T::rank()==2);   template<class T> concept __out_object =// exposition only __is_mdspan<T>::value&&(T::rank()==1|| T::rank()==2)&& is_assignable_v<typename T::reference, typename T::element_type>&& T::is_always_unique();   template<class T> concept __inout_object =// exposition only __is_mdspan<T>::value&&(T::rank()==1|| T::rank()==2)&& is_assignable_v<typename T::reference, typename T::element_type>&& T::is_always_unique();}
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