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template_lapack_larf.h
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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  * Kohn−Sham 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_LARF_HEADER
00036 #define TEMPLATE_LAPACK_LARF_HEADER
00037 
00038 
00039 template<class Treal>
00040 int template_lapack_larf(const char *side, const integer *m, const integer *n, const Treal *v,
00041          const integer *incv, const Treal *tau, Treal *c__, const integer *ldc, 
00042         Treal *work)
00043 {
00044 /*  -- LAPACK auxiliary routine (version 3.0) --   
00045        Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,   
00046        Courant Institute, Argonne National Lab, and Rice University   
00047        February 29, 1992   
00048 
00049 
00050     Purpose   
00051     =======   
00052 
00053     DLARF applies a real elementary reflector H to a real m by n matrix   
00054     C, from either the left or the right. H is represented in the form   
00055 
00056           H = I - tau * v * v'   
00057 
00058     where tau is a real scalar and v is a real vector.   
00059 
00060     If tau = 0, then H is taken to be the unit matrix.   
00061 
00062     Arguments   
00063     =========   
00064 
00065     SIDE    (input) CHARACTER*1   
00066             = 'L': form  H * C   
00067             = 'R': form  C * H   
00068 
00069     M       (input) INTEGER   
00070             The number of rows of the matrix C.   
00071 
00072     N       (input) INTEGER   
00073             The number of columns of the matrix C.   
00074 
00075     V       (input) DOUBLE PRECISION array, dimension   
00076                        (1 + (M-1)*abs(INCV)) if SIDE = 'L'   
00077                     or (1 + (N-1)*abs(INCV)) if SIDE = 'R'   
00078             The vector v in the representation of H. V is not used if   
00079             TAU = 0.   
00080 
00081     INCV    (input) INTEGER   
00082             The increment between elements of v. INCV <> 0.   
00083 
00084     TAU     (input) DOUBLE PRECISION   
00085             The value tau in the representation of H.   
00086 
00087     C       (input/output) DOUBLE PRECISION array, dimension (LDC,N)   
00088             On entry, the m by n matrix C.   
00089             On exit, C is overwritten by the matrix H * C if SIDE = 'L',   
00090             or C * H if SIDE = 'R'.   
00091 
00092     LDC     (input) INTEGER   
00093             The leading dimension of the array C. LDC >= max(1,M).   
00094 
00095     WORK    (workspace) DOUBLE PRECISION array, dimension   
00096                            (N) if SIDE = 'L'   
00097                         or (M) if SIDE = 'R'   
00098 
00099     =====================================================================   
00100 
00101 
00102        Parameter adjustments */
00103     /* Table of constant values */
00104      Treal c_b4 = 1.;
00105      Treal c_b5 = 0.;
00106      integer c__1 = 1;
00107     
00108     /* System generated locals */
00109     integer c_dim1, c_offset;
00110     Treal d__1;
00111 
00112 
00113     --v;
00114     c_dim1 = *ldc;
00115     c_offset = 1 + c_dim1 * 1;
00116     c__ -= c_offset;
00117     --work;
00118 
00119     /* Function Body */
00120     if (template_blas_lsame(side, "L")) {
00121 
00122 /*        Form  H * C */
00123 
00124         if (*tau != 0.) {
00125 
00126 /*           w := C' * v */
00127 
00128             template_blas_gemv("Transpose", m, n, &c_b4, &c__[c_offset], ldc, &v[1], incv,
00129                      &c_b5, &work[1], &c__1);
00130 
00131 /*           C := C - v * w' */
00132 
00133             d__1 = -(*tau);
00134             template_blas_ger(m, n, &d__1, &v[1], incv, &work[1], &c__1, &c__[c_offset], 
00135                     ldc);
00136         }
00137     } else {
00138 
00139 /*        Form  C * H */
00140 
00141         if (*tau != 0.) {
00142 
00143 /*           w := C * v */
00144 
00145             template_blas_gemv("No transpose", m, n, &c_b4, &c__[c_offset], ldc, &v[1], 
00146                     incv, &c_b5, &work[1], &c__1);
00147 
00148 /*           C := C - w * v' */
00149 
00150             d__1 = -(*tau);
00151             template_blas_ger(m, n, &d__1, &work[1], &c__1, &v[1], incv, &c__[c_offset], 
00152                     ldc);
00153         }
00154     }
00155     return 0;
00156 
00157 /*     End of DLARF */
00158 
00159 } /* dlarf_ */
00160 
00161 #endif