| /* Compute {up,n}^(-1). |
| |
| Copyright (C) 2007 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 3 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. If not, see http://www.gnu.org/licenses/. */ |
| |
| #include <stdlib.h> |
| #include "gmp.h" |
| #include "gmp-impl.h" |
| |
| /* Formulas: |
| z = 2z-(zz)d |
| z = 2z-(zd)z |
| z = z(2-zd) |
| z = z-z*(zd-1) |
| z = z+z*(1-zd) |
| */ |
| |
| mp_size_t |
| mpn_invert_itch (mp_size_t n) |
| { |
| return 3 * n + 2; |
| } |
| |
| void |
| mpn_invert (mp_ptr ip, mp_srcptr dp, mp_size_t n, mp_ptr scratch) |
| { |
| mp_ptr np, rp; |
| mp_size_t i; |
| TMP_DECL; |
| |
| TMP_MARK; |
| if (scratch == NULL) |
| { |
| scratch = TMP_ALLOC_LIMBS (mpn_invert_itch (n)); |
| } |
| |
| np = scratch; /* 2 * n limbs */ |
| rp = scratch + 2 * n; /* n + 2 limbs */ |
| for (i = n - 1; i >= 0; i--) |
| np[i] = ~CNST_LIMB(0); |
| mpn_com_n (np + n, dp, n); |
| mpn_tdiv_qr (rp, ip, 0L, np, 2 * n, dp, n); |
| MPN_COPY (ip, rp, n); |
| |
| TMP_FREE; |
| } |