Function dnrm2_subcol (o2scl_cblas)

O2scl : Function List

template<class mat_t>
double o2scl_cblas::dnrm2_subcol(const mat_t &A, const size_t ir, const size_t ic, const size_t M)

Compute the norm of a subcolumn of a matrix.

Given the matrix A, define the vector x as the column with index ic. This function computes the norm of the part of x from row ir to row (inclusive). All other elements in x are not referenced.

if M is zero, then this function silently returns zero without calling the error handler.

This function is used in householder_transform_subcol().

Note

The suffix “2” on the function name indicates that this computes the “2-norm”, not that the norm is squared.