Create A^* A as an operator.

Create A^* A as an operator.

Usage

crossprod_operator(A, name = NULL)

Arguments

A

Operator-like object with an adjoint implementation.

name

Optional label for the cross-product operator.

Value

A Hermitian eigencore_operator representing A^* A.

Details

For a built-in explicit A, A^* A is formed once and wrapped as a native explicit operator (metadata$materialized_crossprod) only when that is cheap and memory-safe: always when it has at most 65,536 entries; for a larger dense A only when A has no more columns than rows and forming it costs at most 2^30 multiply-adds; for a larger sparse A only when a structural bound on its nonzeros stays within four times nnz(A) and below a quarter of its entries (a sparse cross-product is never densified). Otherwise the result is lazy and applies A then its adjoint.