Exact Prediction of QR Fill-In by Row-Merge Trees

نویسنده

Suely Oliveira

چکیده

Row-merge trees for forming the QR factorization of a sparse matrix A are closely related to elimination trees for the Cholesky factorization of ATA. Row-merge trees predict the exact fill-in (assuming no numerical cancellation) provided A satisfies the strong Hall property, but over-estimates the fill-in in general. However, here a fast and simple post-processing step for rowmerge trees is presented that predicts the exact fill-in for sparse QR factorization using Householder reflectors, for general matrices.

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