/usr/include/chemps2/Special.h is in libchemps2-dev 1.8.5-1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 | /*
CheMPS2: a spin-adapted implementation of DMRG for ab initio quantum chemistry
Copyright (C) 2013-2018 Sebastian Wouters
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program 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 General Public License for more details.
You should have received a copy of the GNU General Public License along
with this program; if not, write to the Free Software Foundation, Inc.,
51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
*/
#ifndef SPECIAL_CHEMPS2_H
#define SPECIAL_CHEMPS2_H
namespace CheMPS2{
/** Special class.
\author Sebastian Wouters <sebastianwouters@gmail.com>
\date April 7, 2016
The special class contains static special functions used at various places throughout the code. */
class Special{
public:
//! Phase function
/** \param power_times_two Two times the power of the phase (-1)^{ power }
\return The phase (-1)^{ power_times_two / 2 } */
static int phase( const int power_times_two ){ return (((( power_times_two / 2 ) % 2 ) != 0 ) ? -1 : 1 ); }
//! Triangle function for two variables
/** \param global The triangle counter global = i + ( j * ( j + 1 ) ) / 2 with i <= j
\param result Integer array of size 2 where to store i <= j */
static void invert_triangle_two( const int global, int * result ){
int j = 0;
while ((( j + 1 ) * ( j + 2 )) <= ( 2 * global )){ j++; }
result[ 1 ] = j;
result[ 0 ] = global - ( j * ( j + 1 ) ) / 2;
}
//! LOWER triangle function for two variables
/** \param global The lower triangle counter global = i + ( j * ( j - 1 ) ) / 2 with i < j
\param result Integer array of size 2 where to store i < j */
static void invert_lower_triangle_two( const int global, int * result ){
int j = 1;
while (( j * ( j + 1 )) <= ( 2 * global )){ j++; }
result[ 1 ] = j;
result[ 0 ] = global - ( j * ( j - 1 ) ) / 2;
}
//! Triangle function for three variables
/** \param global The triangle counter global = i + ( j * ( j + 1 ) ) / 2 + ( k * ( k + 1 ) * ( k + 2 ) ) / 6 with i <= j <= k
\param result Integer array of size 3 where to store i <= j <= k */
static void invert_triangle_three( const int global, int * result ){
int k = 0;
while ((( k + 1 ) * ( k + 2 ) * ( k + 3 )) <= ( 6 * global )){ k++; }
const int remainder = global - ( k * ( k + 1 ) * ( k + 2 ) ) / 6;
int j = 0;
while ((( j + 1 ) * ( j + 2 )) <= ( 2 * remainder )){ j++; }
result[ 2 ] = k;
result[ 1 ] = j;
result[ 0 ] = remainder - ( j * ( j + 1 ) ) / 2;
}
};
}
#endif
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