`gr_mat_apply_2x2_rows, gr_mat_apply_2x2_cols`

Synopsis#include <flint/gr_mat.h>

int gr_mat_apply_2x2_rows(gr_mat_t A, slong i1, slong i2, slong c0, slong c1, gr_srcptr M, gr_ctx_t ctx)source

int gr_mat_apply_2x2_cols(gr_mat_t A, slong j1, slong j2, slong r0, slong r1, gr_srcptr M, gr_ctx_t ctx)source

Multiply rows $i_1, i_2$ of $A$ , restricted to the columns $c_0 \le j < c_1$ , on the left by the $2 \times 2$ matrix $M$ (given row by row as a vector of length 4), respectively columns $j_1, j_2$ , restricted to the rows $r_0 \le i < r_1$ , on the right by $M^T$ : the rows (columns) $u, v$ become $M_0 u + M_1 v$ and $M_2 u + M_3 v$ . With $M$ a plane rotation, these are the building blocks of the QR algorithm (Numerical eigenvalues). They call _gr_vec_apply_2x2.

Cite this page

The FLINT team, “gr_mat_apply_2x2_rows, gr_mat_apply_2x2_cols (gr_mat.h),” FLINT: Fast Library for Number Theory, documentation, version 3.7.0-dev, 2026. https://flintlib.org/doc/gr_mat/gr_mat_apply_2x2_rows.html (generated 2026-11-07).

@misc{flint-doc-gr-mat-gr-mat-apply-2x2-rows,
  author       = {{The FLINT team}},
  title        = {{gr\_mat\_apply\_2x2\_rows, gr\_mat\_apply\_2x2\_cols (gr\_mat.h)}},
  howpublished = {FLINT: Fast Library for Number Theory, documentation, version 3.7.0-dev},
  year         = {2026},
  url          = {https://flintlib.org/doc/gr_mat/gr_mat_apply_2x2_rows.html},
  note         = {Generated 2026-11-07}
}

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