cpbsv(3P) Sun Performance Library cpbsv(3P)NAMEcpbsv - compute the solution to a complex system of linear equations A
* X = B,
SYNOPSIS
SUBROUTINE CPBSV(UPLO, N, KD, NRHS, A, LDA, B, LDB, INFO)
CHARACTER * 1 UPLO
COMPLEX A(LDA,*), B(LDB,*)
INTEGER N, KD, NRHS, LDA, LDB, INFO
SUBROUTINE CPBSV_64(UPLO, N, KD, NRHS, A, LDA, B, LDB, INFO)
CHARACTER * 1 UPLO
COMPLEX A(LDA,*), B(LDB,*)
INTEGER*8 N, KD, NRHS, LDA, LDB, INFO
F95 INTERFACE
SUBROUTINE PBSV(UPLO, [N], KD, [NRHS], A, [LDA], B, [LDB], [INFO])
CHARACTER(LEN=1) :: UPLO
COMPLEX, DIMENSION(:,:) :: A, B
INTEGER :: N, KD, NRHS, LDA, LDB, INFO
SUBROUTINE PBSV_64(UPLO, [N], KD, [NRHS], A, [LDA], B, [LDB],
[INFO])
CHARACTER(LEN=1) :: UPLO
COMPLEX, DIMENSION(:,:) :: A, B
INTEGER(8) :: N, KD, NRHS, LDA, LDB, INFO
C INTERFACE
#include <sunperf.h>
void cpbsv(char uplo, int n, int kd, int nrhs, complex *a, int lda,
complex *b, int ldb, int *info);
void cpbsv_64(char uplo, long n, long kd, long nrhs, complex *a, long
lda, complex *b, long ldb, long *info);
PURPOSEcpbsv computes the solution to a complex system of linear equations
A * X = B, where A is an N-by-N Hermitian positive definite band
matrix and X and B are N-by-NRHS matrices.
The Cholesky decomposition is used to factor A as
A = U**H * U, if UPLO = 'U', or
A = L * L**H, if UPLO = 'L',
where U is an upper triangular band matrix, and L is a lower triangular
band matrix, with the same number of superdiagonals or subdiagonals as
A. The factored form of A is then used to solve the system of equa‐
tions A * X = B.
ARGUMENTS
UPLO (input)
= 'U': Upper triangle of A is stored;
= 'L': Lower triangle of A is stored.
N (input) The number of linear equations, i.e., the order of the matrix
A. N >= 0.
KD (input)
The number of superdiagonals of the matrix A if UPLO = 'U',
or the number of subdiagonals if UPLO = 'L'. KD >= 0.
NRHS (input)
The number of right hand sides, i.e., the number of columns
of the matrix B. NRHS >= 0.
A (input/output)
On entry, the upper or lower triangle of the Hermitian 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 A as
follows: if UPLO = 'U', A(KD+1+i-j,j) = A(i,j) for max(1,j-
KD)<=i<=j; if UPLO = 'L', A(1+i-j,j) = A(i,j) for
j<=i<=min(N,j+KD). See below for further details.
On exit, if INFO = 0, the triangular factor U or L from the
Cholesky factorization A = U**H*U or A = L*L**H of the band
matrix A, in the same storage format as A.
LDA (input)
The leading dimension of the array A. LDA >= KD+1.
B (input/output)
On entry, the N-by-NRHS right hand side matrix B. On exit,
if INFO = 0, the N-by-NRHS solution matrix X.
LDB (input)
The leading dimension of the array B. LDB >= max(1,N).
INFO (output)
= 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 of A is not
positive definite, so the factorization could not be com‐
pleted, and the solution has not been computed.
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.
6 Mar 2009 cpbsv(3P)