00001 /* Ergo, version 3.2, a program for linear scaling electronic structure 00002 * calculations. 00003 * Copyright (C) 2012 Elias Rudberg, Emanuel H. Rubensson, and Pawel Salek. 00004 * 00005 * This program is free software: you can redistribute it and/or modify 00006 * it under the terms of the GNU General Public License as published by 00007 * the Free Software Foundation, either version 3 of the License, or 00008 * (at your option) any later version. 00009 * 00010 * This program is distributed in the hope that it will be useful, 00011 * but WITHOUT ANY WARRANTY; without even the implied warranty of 00012 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 00013 * GNU General Public License for more details. 00014 * 00015 * You should have received a copy of the GNU General Public License 00016 * along with this program. If not, see <http://www.gnu.org/licenses/>. 00017 * 00018 * Primary academic reference: 00019 * KohnâSham Density Functional Theory Electronic Structure Calculations 00020 * with Linearly Scaling Computational Time and Memory Usage, 00021 * Elias Rudberg, Emanuel H. Rubensson, and Pawel Salek, 00022 * J. Chem. Theory Comput. 7, 340 (2011), 00023 * <http://dx.doi.org/10.1021/ct100611z> 00024 * 00025 * For further information about Ergo, see <http://www.ergoscf.org>. 00026 */ 00027 00028 /* This file belongs to the template_lapack part of the Ergo source 00029 * code. The source files in the template_lapack directory are modified 00030 * versions of files originally distributed as CLAPACK, see the 00031 * Copyright/license notice in the file template_lapack/COPYING. 00032 */ 00033 00034 00035 #ifndef TEMPLATE_LAPACK_LAPY2_HEADER 00036 #define TEMPLATE_LAPACK_LAPY2_HEADER 00037 00038 00039 template<class Treal> 00040 Treal template_lapack_lapy2(Treal *x, Treal *y) 00041 { 00042 /* -- LAPACK auxiliary routine (version 3.0) -- 00043 Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd., 00044 Courant Institute, Argonne National Lab, and Rice University 00045 October 31, 1992 00046 00047 00048 Purpose 00049 ======= 00050 00051 DLAPY2 returns sqrt(x**2+y**2), taking care not to cause unnecessary 00052 overflow. 00053 00054 Arguments 00055 ========= 00056 00057 X (input) DOUBLE PRECISION 00058 Y (input) DOUBLE PRECISION 00059 X and Y specify the values x and y. 00060 00061 ===================================================================== */ 00062 /* System generated locals */ 00063 Treal ret_val, d__1; 00064 /* Local variables */ 00065 Treal xabs, yabs, w, z__; 00066 00067 00068 00069 xabs = absMACRO(*x); 00070 yabs = absMACRO(*y); 00071 w = maxMACRO(xabs,yabs); 00072 z__ = minMACRO(xabs,yabs); 00073 if (z__ == 0.) { 00074 ret_val = w; 00075 } else { 00076 /* Computing 2nd power */ 00077 d__1 = z__ / w; 00078 ret_val = w * template_blas_sqrt(d__1 * d__1 + 1.); 00079 } 00080 return ret_val; 00081 00082 /* End of DLAPY2 */ 00083 00084 } /* dlapy2_ */ 00085 00086 #endif