// Copyright (C) 2010 Davis E. King (davis@dlib.net)
// License: Boost Software License See LICENSE.txt for the full license.
#ifndef DLIB_LAPACk_BDC_Hh_
#define DLIB_LAPACk_BDC_Hh_
#include "fortran_id.h"
#include "../matrix.h"
namespace dlib
{
namespace lapack
{
namespace binding
{
extern "C"
{
void DLIB_FORTRAN_ID(dpbtrf) (const char *uplo, const integer *n, const integer *kd,
double *ab, const integer *ldab, integer *info);
void DLIB_FORTRAN_ID(spbtrf) (const char *uplo, const integer *n, const integer *kd,
float *ab, const integer *ldab, integer *info);
}
inline integer pbtrf (const char uplo, const integer n, const integer kd,
double* ab, const integer ldab)
{
integer info = 0;
DLIB_FORTRAN_ID(dpbtrf)(&uplo, &n, &kd, ab, &ldab, &info);
return info;
}
inline integer pbtrf (const char uplo, const integer n, const integer kd,
float* ab, const integer ldab)
{
integer info = 0;
DLIB_FORTRAN_ID(spbtrf)(&uplo, &n, &kd, ab, &ldab, &info);
return info;
}
}
// ------------------------------------------------------------------------------------
/* DPBTRF(l) LAPACK routine (version 1.1) DPBTRF(l)
NAME
DPBTRF - compute the Cholesky factorization of a real symmetric positive
definite band matrix A
SYNOPSIS
SUBROUTINE DPBTRF( UPLO, N, KD, AB, LDAB, INFO )
CHARACTER UPLO
INTEGER INFO, KD, LDAB, N
DOUBLE PRECISION AB( LDAB, * )
PURPOSE
DPBTRF computes the Cholesky factorization of a real symmetric positive
definite band matrix A.
The factorization has the form
A = U**T * U, if UPLO = 'U', or
A = L * L**T, if UPLO = 'L',
where U is an upper triangular matrix and L is lower triangular.
ARGUMENTS
UPLO (input) CHARACTER*1
= 'U': Upper triangle of A is stored;
= 'L': Lower triangle of A is stored.
N (input) INTEGER
The order of the matrix A. N >= 0.
KD (input) INTEGER
The number of superdiagonals of the matrix A if UPLO = 'U', or the
number of subdiagonals if UPLO = 'L'. KD >= 0.
AB (input/output) DOUBLE PRECISION array, dimension (LDAB,N)
On entry, the upper or lower triangle of the symmetric band matrix
A, stored in the first KD+1 rows of the array. The j-th column of
A is stored in the j-th column of the array AB as follows: if UPLO
= 'U', AB(kd+1+i-j,j) = A(i,j) for max(1,j-kd)<=i<=j; if UPLO =
'L', AB(1+i-j,j) = A(i,j) for j<=i<=min(n,j+kd).
On exit, if INFO = 0, the triangular factor U or L from the Chole-
sky factorization A = U**T*U or A = L*L**T of the band matrix A, in
the same storage format as A.
LDAB (input) INTEGER
The leading dimension of the array AB. LDAB >= KD+1.
INFO (output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: if INFO = i, the leading minor of order i is not positive
definite, and the factorization could not be completed.
FURTHER DETAILS
The band storage scheme is illustrated by the following example, when N =
6, KD = 2, and UPLO = 'U':
On entry: On exit:
* * a13 a24 a35 a46 * * u13 u24 u35 u46
* a12 a23 a34 a45 a56 * u12 u23 u34 u45 u56
a11 a22 a33 a44 a55 a66 u11 u22 u33 u44 u55 u66
Similarly, if UPLO = 'L' the format of A is as follows:
On entry: On exit:
a11 a22 a33 a44 a55 a66 l11 l22 l33 l44 l55 l66
a21 a32 a43 a54 a65 * l21 l32 l43 l54 l65 *
a31 a42 a53 a64 * * l31 l42 l53 l64 * *
Array elements marked * are not used by the routine.
Contributed by
Peter Mayes and Giuseppe Radicati, IBM ECSEC, Rome, March 23, 1989 */
// ------------------------------------------------------------------------------------
template <
typename T,
long NR1, long NC1,
typename MM
>
int pbtrf (
char uplo, matrix<T,NR1,NC1,MM,column_major_layout>& ab
)
{
const long ldab = ab.nr();
const long n = ab.nc();
const long kd = ldab - 1; // assume fully packed
int info = binding::pbtrf(uplo, n, kd, &ab(0,0), ldab);
return info;
}
// ------------------------------------------------------------------------------------
template <
typename T,
long NR1, long NC1,
typename MM
>
int pbtrf (
char uplo, matrix<T,NR1,NC1,MM,row_major_layout>& ab
)
{
const long ldab = ab.nr();
const long n = ab.nc();
const long kd = ldab - 1; // assume fully packed
matrix<T,NC1,NR1,MM,row_major_layout> abt = trans(ab);
int info = binding::pbtrf(uplo, n, kd, &abt(0,0), ldab);
ab = trans(abt);
return info;
}
// ------------------------------------------------------------------------------------
}
}
// ----------------------------------------------------------------------------------------
#endif // DLIB_LAPACk_BDC_Hh_