65 lines
2.1 KiB
C
65 lines
2.1 KiB
C
/*
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Copyright 2009 Jason Moxham
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This file is part of the MPIR Library.
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The MPIR Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published
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by the Free Software Foundation; either version 2.1 of the License, or (at
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your option) any later version.
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The MPIR Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the MPIR Library; see the file COPYING.LIB. If not, write
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to the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
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Boston, MA 02110-1301, USA.
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*/
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#include "mpir.h"
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#include "gmp-impl.h"
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#include "longlong.h"
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// using a two limb inverse of a one limb divisor
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mp_limb_t mpn_rsh_divrem_hensel_qr_1_2(mp_ptr qp, mp_srcptr xp, mp_size_t n, mp_limb_t d,int s,mp_limb_t cin)
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{mp_size_t j;mp_limb_t c,h,q,dummy,h1,t,ml,mh,xl,xh,ql,qh,qo;
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ASSERT(n>=2);ASSERT_MPN(xp,n);ASSERT(MPN_SAME_OR_SEPARATE_P(qp,xp,n));
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ASSERT(d%2==1);ASSERT(s>=0);
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modlimb_invert(ml,d);
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umul_ppmm(h,dummy,d,ml);ASSERT(dummy==1);
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h=-h;mh=ml*h;// (mh,ml) is our two limb inverse
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h1=xp[0];h=cin;c=0;
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t=h+c;if(t>h1){h1=h1-t;c=1;}else{h1=h1-t;c=0;}
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q=h1*ml;
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qo=q>>s;
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umul_ppmm(h,dummy,q,d);
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for(j=1;j+1<=n-1;j+=2)
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{xl=xp[j];xh=xp[j+1];
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t=h+c;if(xh==0 && t>xl){c=1;}else{c=0;}
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sub_ddmmss(xh,xl,xh,xl,0,t);
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umul_ppmm(qh,ql,xl,ml);
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qh=qh+xh*ml+xl*mh;
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qo=qo|(ql<<(GMP_LIMB_BITS-1-s)<<1);
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qp[j-1]=qo;qo=ql>>s;//qp[j]=ql;
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qo=qo|(qh<<(GMP_LIMB_BITS-1-s)<<1);
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qp[j+1-1]=qo;qo=qh>>s;//qp[j+1]=qh;
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umul_ppmm(h,h1,qh,d);
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if(h1>xh)h++;}
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if(j<=n-1)
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{h1=xp[j];
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t=h+c;if(t>h1){h1=h1-t;c=1;}else{h1=h1-t;c=0;}
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q=h1*ml;
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qo=qo|(q<<(GMP_LIMB_BITS-1-s)<<1);
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qp[j-1]=qo;qo=q>>s;//qp[j]=q;
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umul_ppmm(h,dummy,q,d);
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ASSERT(dummy==h1);}
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qp[n-1]=qo;
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return h+c;} // so (xp,n) = (qp,n)*d -ret*B^n and 0 <= ret < d
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