/usr/include/eigen3/Eigen/src/SparseLU/SparseLU_pivotL.h is in libeigen3-dev 3.2.2-3.
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 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 | // This file is part of Eigen, a lightweight C++ template library
// for linear algebra.
//
// Copyright (C) 2012 Désiré Nuentsa-Wakam <desire.nuentsa_wakam@inria.fr>
//
// This Source Code Form is subject to the terms of the Mozilla
// Public License v. 2.0. If a copy of the MPL was not distributed
// with this file, You can obtain one at http://mozilla.org/MPL/2.0/.
/*
* NOTE: This file is the modified version of xpivotL.c file in SuperLU
* -- SuperLU routine (version 3.0) --
* Univ. of California Berkeley, Xerox Palo Alto Research Center,
* and Lawrence Berkeley National Lab.
* October 15, 2003
*
* Copyright (c) 1994 by Xerox Corporation. All rights reserved.
*
* THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY
* EXPRESSED OR IMPLIED. ANY USE IS AT YOUR OWN RISK.
*
* Permission is hereby granted to use or copy this program for any
* purpose, provided the above notices are retained on all copies.
* Permission to modify the code and to distribute modified code is
* granted, provided the above notices are retained, and a notice that
* the code was modified is included with the above copyright notice.
*/
#ifndef SPARSELU_PIVOTL_H
#define SPARSELU_PIVOTL_H
namespace Eigen {
namespace internal {
/**
* \brief Performs the numerical pivotin on the current column of L, and the CDIV operation.
*
* Pivot policy :
* (1) Compute thresh = u * max_(i>=j) abs(A_ij);
* (2) IF user specifies pivot row k and abs(A_kj) >= thresh THEN
* pivot row = k;
* ELSE IF abs(A_jj) >= thresh THEN
* pivot row = j;
* ELSE
* pivot row = m;
*
* Note: If you absolutely want to use a given pivot order, then set u=0.0.
*
* \param jcol The current column of L
* \param diagpivotthresh diagonal pivoting threshold
* \param[in,out] perm_r Row permutation (threshold pivoting)
* \param[in] iperm_c column permutation - used to finf diagonal of Pc*A*Pc'
* \param[out] pivrow The pivot row
* \param glu Global LU data
* \return 0 if success, i > 0 if U(i,i) is exactly zero
*
*/
template <typename Scalar, typename Index>
Index SparseLUImpl<Scalar,Index>::pivotL(const Index jcol, const RealScalar& diagpivotthresh, IndexVector& perm_r, IndexVector& iperm_c, Index& pivrow, GlobalLU_t& glu)
{
Index fsupc = (glu.xsup)((glu.supno)(jcol)); // First column in the supernode containing the column jcol
Index nsupc = jcol - fsupc; // Number of columns in the supernode portion, excluding jcol; nsupc >=0
Index lptr = glu.xlsub(fsupc); // pointer to the starting location of the row subscripts for this supernode portion
Index nsupr = glu.xlsub(fsupc+1) - lptr; // Number of rows in the supernode
Index lda = glu.xlusup(fsupc+1) - glu.xlusup(fsupc); // leading dimension
Scalar* lu_sup_ptr = &(glu.lusup.data()[glu.xlusup(fsupc)]); // Start of the current supernode
Scalar* lu_col_ptr = &(glu.lusup.data()[glu.xlusup(jcol)]); // Start of jcol in the supernode
Index* lsub_ptr = &(glu.lsub.data()[lptr]); // Start of row indices of the supernode
// Determine the largest abs numerical value for partial pivoting
Index diagind = iperm_c(jcol); // diagonal index
RealScalar pivmax = 0.0;
Index pivptr = nsupc;
Index diag = emptyIdxLU;
RealScalar rtemp;
Index isub, icol, itemp, k;
for (isub = nsupc; isub < nsupr; ++isub) {
rtemp = std::abs(lu_col_ptr[isub]);
if (rtemp > pivmax) {
pivmax = rtemp;
pivptr = isub;
}
if (lsub_ptr[isub] == diagind) diag = isub;
}
// Test for singularity
if ( pivmax == 0.0 ) {
pivrow = lsub_ptr[pivptr];
perm_r(pivrow) = jcol;
return (jcol+1);
}
RealScalar thresh = diagpivotthresh * pivmax;
// Choose appropriate pivotal element
{
// Test if the diagonal element can be used as a pivot (given the threshold value)
if (diag >= 0 )
{
// Diagonal element exists
rtemp = std::abs(lu_col_ptr[diag]);
if (rtemp != 0.0 && rtemp >= thresh) pivptr = diag;
}
pivrow = lsub_ptr[pivptr];
}
// Record pivot row
perm_r(pivrow) = jcol;
// Interchange row subscripts
if (pivptr != nsupc )
{
std::swap( lsub_ptr[pivptr], lsub_ptr[nsupc] );
// Interchange numerical values as well, for the two rows in the whole snode
// such that L is indexed the same way as A
for (icol = 0; icol <= nsupc; icol++)
{
itemp = pivptr + icol * lda;
std::swap(lu_sup_ptr[itemp], lu_sup_ptr[nsupc + icol * lda]);
}
}
// cdiv operations
Scalar temp = Scalar(1.0) / lu_col_ptr[nsupc];
for (k = nsupc+1; k < nsupr; k++)
lu_col_ptr[k] *= temp;
return 0;
}
} // end namespace internal
} // end namespace Eigen
#endif // SPARSELU_PIVOTL_H
|