There is a small old bug in mpz_powm, which can be detected with the
following program:
#include "gmp-impl.h"
int
main (int argc, char *argv[])
{
mpz_t M, N, E;
mpz_init_set_ui (M, 1);
mpz_init_set_ui (E, 1);
mpz_init (N);
mpz_setbit (M, 10 * GMP_NUMB_BITS);
mpz_setbit (M, 0);
mpz_ui_sub (N, 17, M);
mpz_powm (N, N, E, M);
MPZ_CHECK_FORMAT (N);
mpz_clear (M);
mpz_clear (N);
mpz_clear (E);
}
I'd suggest the following patch:
diff -r 2109bbf292bd mpz/powm.c
--- a/mpz/powm.c Thu Dec 05 07:44:46 2019 +0100
+++ b/mpz/powm.c Sun Dec 08 17:27:56 2019 +0100
@@ -138,7 +138,7 @@
{
mpn_sub (rp, mp, n, bp, bn);
rn = n;
- rn -= (rp[rn - 1] == 0);
+ MPN_NORMALIZE_NOT_ZERO (rp, rn);
}
else
{
Ĝis,
m
--
http://bodrato.it/papers/
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