`n_ll_factor_ecm`

Synopsis#include <flint/ulong_extras.h>

int n_ll_factor_ecm(nn_ptr factor, ulong nhi, ulong nlo, ulong curves, ulong B1, ulong B2, flint_rand_t state)source

The elliptic curve method for an odd two-limb $n$ with $n_{hi} \ne 0$ , trying up to curves curves with bounds $B_1$ , $B_2$ (if $B_2 < B_1$ , then $100 B_1$ is used). Returns 1 and writes a factor on success, otherwise 0.

Curves use Suyama's parametrisation. Both stages run in two-limb Montgomery arithmetic, roughly twice as fast as fmpz_factor_ecm with the same parameters for $n$ of this size.

Cite this page

The FLINT team, “n_ll_factor_ecm (ulong_extras.h),” FLINT: Fast Library for Number Theory, documentation, version 3.7.0-dev, 2026. https://flintlib.org/doc/ulong_extras/n_ll_factor_ecm.html (generated 2026-11-02).

@misc{flint-doc-ulong-extras-n-ll-factor-ecm,
  author       = {{The FLINT team}},
  title        = {{n\_ll\_factor\_ecm (ulong\_extras.h)}},
  howpublished = {FLINT: Fast Library for Number Theory, documentation, version 3.7.0-dev},
  year         = {2026},
  url          = {https://flintlib.org/doc/ulong_extras/n_ll_factor_ecm.html},
  note         = {Generated 2026-11-02}
}

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