[Gmp-commit] /var/hg/gmp: mpz/stronglucas.c: Add a comment

[mercurial at gmplib.org]

details:   /var/hg/gmp/rev/58bb9b017366
changeset: 18361:58bb9b017366
user:      Marco Bodrato <bodrato at mail.dm.unipi.it>
date:      Sun May 29 18:08:56 2022 +0200
description:
mpz/stronglucas.c: Add a comment

diffstat:

 mpz/stronglucas.c |  5 +++--
 1 files changed, 3 insertions(+), 2 deletions(-)

diffs (29 lines):

diff -r 61ef108d740c -r 58bb9b017366 mpz/stronglucas.c
--- a/mpz/stronglucas.c	Sun May 29 16:16:47 2022 +0200
+++ b/mpz/stronglucas.c	Sun May 29 18:08:56 2022 +0200
@@ -122,6 +122,7 @@
   /* (2^24 - 1) | (2^{GMP_NUMB_BITS*3/4} - 1)	*/
   /* (2^24 - 1) = (2^12 - 1) * 17 * 241		*/
   else if (! POW2_P (g % 17) && ! POW2_P (17 - g % 17))
+    /* (17/n) = -1, iff n != +-1,+-2,+-4,+-8 (mod 17)	*/
     D = 17; /* Q = -4 */
 #endif
 #else
@@ -179,7 +180,7 @@
   /* If Ud != 0 && Vd != 0 */
   if (mpz_lucas_mod (V, Qk, Q, b0, n, T1, T2) == 0)
     if (LIKELY (--b0 != 0))
-      do
+      for (;;)
 	{
 	  /* V_{2k} <- V_k ^ 2 - 2Q^k */
 	  mpz_mul (T2, V, V);
@@ -190,7 +191,7 @@
 	  /* Q^{2k} = (Q^k)^2 */
 	  mpz_mul (T2, Qk, Qk);
 	  mpz_tdiv_r (Qk, T2, n);
-	} while (1);
+	}
 
   mpz_clear (T1);
   mpz_clear (T2);