/usr/share/doc/libecm0-dev-common/examples/ecmfactor.c is in libecm0-dev-common 6.4.4+ds-5.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 | /* ecmfactor.c - example of use of the ECM library.
Copyright 2005, 2006 Paul Zimmermann, Dave Newman.
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 3 of the License, or (at your
option) any later version.
This program is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
more details.
You should have received a copy of the GNU General Public License
along with this program; see the file COPYING. If not, see
http://www.gnu.org/licenses/ or write to the Free Software Foundation, Inc.,
51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA. */
#include <stdio.h>
#include <stdlib.h>
#include <gmp.h> /* GMP header file */
#include <ecm.h> /* ecm header file */
int
main (int argc, char *argv[])
{
mpz_t n, f;
int res;
double B1;
if (argc != 3)
{
fprintf (stderr, "Usage: ecmfactor <number> <B1>\n");
exit (1);
}
mpz_init (n);
/* read number on command line */
if (mpz_set_str (n, argv[1], 10))
{
fprintf (stderr, "Invalid number: %s\n", argv[1]);
exit (1);
}
B1 = atof (argv[2]);
mpz_init (f); /* for potential factor */
printf ("Performing one curve with B1=%1.0f\n", B1);
res = ecm_factor (f, n, B1, NULL);
if (res > 0)
{
printf ("found factor in step %u: ", res);
mpz_out_str (stdout, 10, f);
printf ("\n");
#if 0
printf ("lucky curve was b*y^2 = x^3 + a*x^2 + x\n");
printf ("with a = (v-u)^3*(3*u+v)/(4*u^3*v)-2,");
printf (" u = sigma^2-5, v = 4*sigma\n");
#endif
}
else if (res == ECM_NO_FACTOR_FOUND)
printf ("found no factor\n");
else
printf ("error\n");
mpz_clear (f);
mpz_clear (n);
return 0;
}
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