mirror of
https://github.com/triqs/dft_tools
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66 lines
2.8 KiB
C++
66 lines
2.8 KiB
C++
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/*******************************************************************************
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*
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* TRIQS: a Toolbox for Research in Interacting Quantum Systems
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*
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* Copyright (C) 2011 by O. Parcollet
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*
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* TRIQS is free software: you can redistribute it and/or modify it under the
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* terms of the GNU General Public License as published by the Free Software
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* Foundation, either version 3 of the License, or (at your option) any later
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* version.
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*
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* TRIQS is distributed in the hope that it will be useful, but WITHOUT ANY
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* WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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* details.
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*
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* You should have received a copy of the GNU General Public License along with
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* TRIQS. If not, see <http://www.gnu.org/licenses/>.
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*
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******************************************************************************/
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#ifndef TRIQS_ARRAYS_PERMUTATIONS2_H
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#define TRIQS_ARRAYS_PERMUTATIONS2_H
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namespace triqs { namespace arrays { namespace permutations {
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typedef unsigned long long ull;
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constexpr ull apply(ull p, ull i) { return (p >> (4*(i+1))) & 0xFull;}
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constexpr ull size( ull p) { return p & 0xFull;}
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inline ull permutation_from_array ( const int * const p, int length) {
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ull res =0;
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for (int i =length-1; i>=0; --i) res = p[i] + 0x10*res;
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res= 0x10 * res + length;
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return res;
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}
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// sum_{k=0}^{n-1} k a^k = ( (n-1) * a**(n+1) - n * a**n + a)/(a-1)**2
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// sum_{k=0}^{n-1} k a^(n-k-1) = ( (n-1) - n * a + a**n)/(a-1)**2
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// with a = 16, a**n = 1<<4n
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constexpr ull _identity(ull n) { return ( (n-1ull)*(1ull<<(4*(n+1))) +(1ull<<4)- n *(1ull<<(4*n))) /( (1ull<<4) -1ull) /((1ull<<4) -1ull); }
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constexpr ull identity(ull n) { return n + 0x10 * _identity(n);}
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constexpr ull _ridentity(ull n) { return ( (n-1ull) - n* (1ull<<4) + (1ull<<(4*n))) /( (1ull<<4) -1ull) /((1ull<<4) -1ull); }
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constexpr ull ridentity(ull n) { return n + 0x10 *_ridentity(n); }
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constexpr ull make_perm_impl(){ return 0;}
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template<typename ... T> constexpr ull make_perm_impl(ull i0, T... x) { return i0 + 0x10 * make_perm_impl(x...); }
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template<typename ... T> constexpr ull permutation(T... x) { return ull(sizeof...(T)) + 0x10* make_perm_impl(x...); }
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constexpr ull compose_impl(ull p1, ull p2, ull c) { return apply(p2, apply(p1,c)) + 16ull * ( (c+1 <size(p1) ? compose_impl(p1,p2,c+1ull) : 0)); }
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constexpr ull compose(ull p1, ull p2) { return size(p1) + 0x10* compose_impl(p1,p2, 0);}
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constexpr ull inverse_impl(ull p, ull c) { return (c << (4*apply(p,c))) + (c>0 ? inverse_impl(p,c-1): 0 ); }
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constexpr ull inverse(ull p) { return size(p) + 0x10ull*inverse_impl(p,size(p)-1);}
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inline void print( std::ostream & out, ull perm) {
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out << "(";
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for (int i =0; i< permutations::size(perm); ++i) { out << (i!=0 ? " " : "") << apply(perm,i);}
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out << ")";
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}
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}
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using permutations::permutation;
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}}
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#endif
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