diff options
Diffstat (limited to 'rts/gmp/mpn/generic/perfsqr.c')
-rw-r--r-- | rts/gmp/mpn/generic/perfsqr.c | 123 |
1 files changed, 123 insertions, 0 deletions
diff --git a/rts/gmp/mpn/generic/perfsqr.c b/rts/gmp/mpn/generic/perfsqr.c new file mode 100644 index 0000000000..42ee3405d7 --- /dev/null +++ b/rts/gmp/mpn/generic/perfsqr.c @@ -0,0 +1,123 @@ +/* mpn_perfect_square_p(u,usize) -- Return non-zero if U is a perfect square, + zero otherwise. + +Copyright (C) 1991, 1993, 1994, 1996, 1997, 2000 Free Software Foundation, +Inc. + +This file is part of the GNU MP Library. + +The GNU MP Library is free software; you can redistribute it and/or modify +it under the terms of the GNU Lesser General Public License as published by +the Free Software Foundation; either version 2.1 of the License, or (at your +option) any later version. + +The GNU MP Library 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 Lesser General Public +License for more details. + +You should have received a copy of the GNU Lesser General Public License +along with the GNU MP Library; see the file COPYING.LIB. If not, write to +the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, +MA 02111-1307, USA. */ + +#include <stdio.h> /* for NULL */ +#include "gmp.h" +#include "gmp-impl.h" +#include "longlong.h" + + +/* sq_res_0x100[x mod 0x100] == 1 iff x mod 0x100 is a quadratic residue + modulo 0x100. */ +static unsigned char const sq_res_0x100[0x100] = +{ + 1,1,0,0,1,0,0,0,0,1,0,0,0,0,0,0,1,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0, + 0,1,0,0,1,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0, + 1,1,0,0,1,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0, + 0,1,0,0,1,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0, + 0,1,0,0,1,0,0,0,0,1,0,0,0,0,0,0,1,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0, + 0,1,0,0,1,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0, + 0,1,0,0,1,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0, + 0,1,0,0,1,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,1,0,0,0,0,0,0, +}; + +int +#if __STDC__ +mpn_perfect_square_p (mp_srcptr up, mp_size_t usize) +#else +mpn_perfect_square_p (up, usize) + mp_srcptr up; + mp_size_t usize; +#endif +{ + mp_limb_t rem; + mp_ptr root_ptr; + int res; + TMP_DECL (marker); + + /* The first test excludes 55/64 (85.9%) of the perfect square candidates + in O(1) time. */ + if ((sq_res_0x100[(unsigned int) up[0] % 0x100] & 1) == 0) + return 0; + +#if defined (PP) + /* The second test excludes 30652543/30808063 (99.5%) of the remaining + perfect square candidates in O(n) time. */ + + /* Firstly, compute REM = A mod PP. */ + if (UDIV_TIME > (2 * UMUL_TIME + 6)) + rem = mpn_preinv_mod_1 (up, usize, (mp_limb_t) PP, (mp_limb_t) PP_INVERTED); + else + rem = mpn_mod_1 (up, usize, (mp_limb_t) PP); + + /* Now decide if REM is a quadratic residue modulo the factors in PP. */ + + /* If A is just a few limbs, computing the square root does not take long + time, so things might run faster if we limit this loop according to the + size of A. */ + +#if BITS_PER_MP_LIMB == 64 + if (((CNST_LIMB(0x12DD703303AED3) >> rem % 53) & 1) == 0) + return 0; + if (((CNST_LIMB(0x4351B2753DF) >> rem % 47) & 1) == 0) + return 0; + if (((CNST_LIMB(0x35883A3EE53) >> rem % 43) & 1) == 0) + return 0; + if (((CNST_LIMB(0x1B382B50737) >> rem % 41) & 1) == 0) + return 0; + if (((CNST_LIMB(0x165E211E9B) >> rem % 37) & 1) == 0) + return 0; + if (((CNST_LIMB(0x121D47B7) >> rem % 31) & 1) == 0) + return 0; +#endif + if (((0x13D122F3L >> rem % 29) & 1) == 0) + return 0; + if (((0x5335FL >> rem % 23) & 1) == 0) + return 0; + if (((0x30AF3L >> rem % 19) & 1) == 0) + return 0; + if (((0x1A317L >> rem % 17) & 1) == 0) + return 0; + if (((0x161BL >> rem % 13) & 1) == 0) + return 0; + if (((0x23BL >> rem % 11) & 1) == 0) + return 0; + if (((0x017L >> rem % 7) & 1) == 0) + return 0; + if (((0x13L >> rem % 5) & 1) == 0) + return 0; + if (((0x3L >> rem % 3) & 1) == 0) + return 0; +#endif + + TMP_MARK (marker); + + /* For the third and last test, we finally compute the square root, + to make sure we've really got a perfect square. */ + root_ptr = (mp_ptr) TMP_ALLOC ((usize + 1) / 2 * BYTES_PER_MP_LIMB); + + /* Iff mpn_sqrtrem returns zero, the square is perfect. */ + res = ! mpn_sqrtrem (root_ptr, NULL, up, usize); + TMP_FREE (marker); + return res; +} |