1 /* mpf_reldiff -- Generate the relative difference of two floats. 2 3 Copyright 1996, 2001, 2004, 2005 Free Software Foundation, Inc. 4 5 This file is part of the GNU MP Library. 6 7 The GNU MP Library is free software; you can redistribute it and/or modify 8 it under the terms of the GNU Lesser General Public License as published by 9 the Free Software Foundation; either version 3 of the License, or (at your 10 option) any later version. 11 12 The GNU MP Library is distributed in the hope that it will be useful, but 13 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 14 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 15 License for more details. 16 17 You should have received a copy of the GNU Lesser General Public License 18 along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */ 19 20 #include "gmp.h" 21 #include "gmp-impl.h" 22 23 24 /* The precision we use for d = x-y is based on what mpf_div will want from 25 the dividend. It calls mpn_tdiv_qr to produce a quotient of rprec+1 26 limbs. So rprec+1 == dsize - xsize + 1, hence dprec = rprec+xsize. */ 27 28 void 29 mpf_reldiff (mpf_t rdiff, mpf_srcptr x, mpf_srcptr y) 30 { 31 if (UNLIKELY (SIZ(x) == 0)) 32 { 33 mpf_set_ui (rdiff, (unsigned long int) (mpf_sgn (y) != 0)); 34 } 35 else 36 { 37 mp_size_t dprec; 38 mpf_t d; 39 TMP_DECL; 40 41 TMP_MARK; 42 dprec = PREC(rdiff) + ABSIZ(x); 43 ASSERT (PREC(rdiff)+1 == dprec - ABSIZ(x) + 1); 44 45 PREC(d) = dprec; 46 PTR(d) = TMP_ALLOC_LIMBS (dprec + 1); 47 48 mpf_sub (d, x, y); 49 SIZ(d) = ABSIZ(d); 50 mpf_div (rdiff, d, x); 51 52 TMP_FREE; 53 } 54 } 55