80 lines
2.6 KiB
C++
80 lines
2.6 KiB
C++
/*
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LA: linear algebra C++ interface library
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Copyright (C) 2008 Jiri Pittner <jiri.pittner@jh-inst.cas.cz> or <jiri@pittnerovi.com>
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef _BISECTION_H
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#define _BISECTION_H
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//general bisection search between dm and hm
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//returns dm-1 on failure, otherwise number between dm and hm
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//cmp returns 0 on equal, >0 if first > second argument
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template<typename INDEX, typename COMPAR, typename SUBJECT>
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INDEX bisection_find(INDEX dm, INDEX hm, const SUBJECT *key, const SUBJECT *base , unsigned int lead_dimension_base, COMPAR (*cmp)(const SUBJECT *, const SUBJECT *))
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{
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if(dm>hm) return(dm-1);
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if(dm==hm) return (*cmp)(base+dm*lead_dimension_base,key)? dm-1 :dm;
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INDEX sm;
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INDEX dm0=dm;
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--dm;
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++hm;
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do
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{
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sm = (dm+hm)/2;
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COMPAR q = (*cmp)(base+sm*lead_dimension_base,key);
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if (!q) return(sm);
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else if (q<0) dm = sm; else hm = sm;
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}
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while (hm > dm+1);
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return(dm0-1);
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}
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// interpolation search
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//distance is +-0, on its quality the convergence speed depends
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template<typename INDEX, typename DISTANCE, typename SUBJECT>
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int interpolation_find(INDEX dm0, INDEX high, const SUBJECT *x, const SUBJECT *base , unsigned int lead_dimension_base, DISTANCE (*dist)(const SUBJECT *, const SUBJECT *))
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{
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INDEX low = dm0;
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INDEX mid;
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DISTANCE d1,d2,d3,d4;
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while(1)
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{
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d1=(*dist)(x,base+low*lead_dimension_base);
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d2=(*dist)(base+high*lead_dimension_base,x);
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if(d1<=0 || d2 <=0) break;
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d3=(*dist)(base+high*lead_dimension_base,base+low*lead_dimension_base);
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mid = low + (int)((d1 * (high-low)) / d3);
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if(mid<low||mid>high) laerror("interpolation_find: error in distance function");
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d4=(*dist)(x,base+mid*lead_dimension_base);
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if(d4>0)
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low = mid + 1;
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else if(d4<0)
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high = mid - 1;
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else
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return mid;
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}
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if (d1==0) return low;
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if (d2==0) return high;
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return dm0-1; // Not found
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}
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#endif
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