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/* Ergo, version 3.5, a program for linear scaling electronic structure
* calculations.
* Copyright (C) 2016 Elias Rudberg, Emanuel H. Rubensson, Pawel Salek,
* and Anastasia Kruchinina.
*
* 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 3 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, see <http://www.gnu.org/licenses/>.
*
* Primary academic reference:
* KohnâSham Density Functional Theory Electronic Structure Calculations
* with Linearly Scaling Computational Time and Memory Usage,
* Elias Rudberg, Emanuel H. Rubensson, and Pawel Salek,
* J. Chem. Theory Comput. 7, 340 (2011),
* <http://dx.doi.org/10.1021/ct100611z>
*
* For further information about Ergo, see <http://www.ergoscf.org>.
*/
#include "machine_epsilon.h"
/** return machine epsilon. This routine is deprecated. Use instead:
- std::numeric_limits<double>::epsilon() in C++;
- or FLT_EPSILON for single precision, DBL_EPSILON for double
precision or or LDBL_EPSILON in long double - in C.
*/
ergo_real
get_machine_epsilon()
{
ergo_real volatile x, y, z;
x = 1;
y = 0.1;
while(1)
{
z = x + y;
if(z == x)
return y;
y *= 0.98;
}
/* this point should never be reached */
return 0;
}
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