---
name: "csbmv.f"
section: "3"
platform: "linux"
package: "lapack-doc"
version: "3.12.1-2"
release: "Arch Linux 2026-11-01"
platforms: ["linux"]
url: "https://new.carta.tech/csbmv.f"
---

# csbmv.f(3)

## NAME

TESTING/LIN/csbmv.f

## SYNOPSIS

### Functions/Subroutines

subroutine **csbmv** (uplo, n, k, alpha, a, lda, x, incx, beta, y, incy)\
 **CSBMV**

## Function/Subroutine Documentation

### subroutine csbmv (character uplo, integer n, integer k, complex alpha, complex, dimension( lda, \* ) a, integer lda, complex, dimension( \* ) x, integer incx, complex beta, complex, dimension( \* ) y, integer incy)

**CSBMV**

**Purpose:**

```
!>
!> CSBMV  performs the matrix-vector  operation
!>
!>    y := alpha*A*x + beta*y,
!>
!> where alpha and beta are scalars, x and y are n element vectors and
!> A is an n by n symmetric band matrix, with k super-diagonals.
!>
```

```
!>  UPLO   - CHARACTER*1
!>           On entry, UPLO specifies whether the upper or lower
!>           triangular part of the band matrix A is being supplied as
!>           follows:
!>
!>              UPLO = 'U' or 'u'   The upper triangular part of A is
!>                                  being supplied.
!>
!>              UPLO = 'L' or 'l'   The lower triangular part of A is
!>                                  being supplied.
!>
!>           Unchanged on exit.
!>
!>  N      - INTEGER
!>           On entry, N specifies the order of the matrix A.
!>           N must be at least zero.
!>           Unchanged on exit.
!>
!>  K      - INTEGER
!>           On entry, K specifies the number of super-diagonals of the
!>           matrix A. K must satisfy  0 .le. K.
!>           Unchanged on exit.
!>
!>  ALPHA  - COMPLEX
!>           On entry, ALPHA specifies the scalar alpha.
!>           Unchanged on exit.
!>
!>  A      - COMPLEX array, dimension( LDA, N )
!>           Before entry with UPLO = 'U' or 'u', the leading ( k + 1 )
!>           by n part of the array A must contain the upper triangular
!>           band part of the symmetric matrix, supplied column by
!>           column, with the leading diagonal of the matrix in row
!>           ( k + 1 ) of the array, the first super-diagonal starting at
!>           position 2 in row k, and so on. The top left k by k triangle
!>           of the array A is not referenced.
!>           The following program segment will transfer the upper
!>           triangular part of a symmetric band matrix from conventional
!>           full matrix storage to band storage:
!>
!>                 DO 20, J = 1, N
!>                    M = K + 1 - J
!>                    DO 10, I = MAX( 1, J - K ), J
!>                       A( M + I, J ) = matrix( I, J )
!>              10    CONTINUE
!>              20 CONTINUE
!>
!>           Before entry with UPLO = 'L' or 'l', the leading ( k + 1 )
!>           by n part of the array A must contain the lower triangular
!>           band part of the symmetric matrix, supplied column by
!>           column, with the leading diagonal of the matrix in row 1 of
!>           the array, the first sub-diagonal starting at position 1 in
!>           row 2, and so on. The bottom right k by k triangle of the
!>           array A is not referenced.
!>           The following program segment will transfer the lower
!>           triangular part of a symmetric band matrix from conventional
!>           full matrix storage to band storage:
!>
!>                 DO 20, J = 1, N
!>                    M = 1 - J
!>                    DO 10, I = J, MIN( N, J + K )
!>                       A( M + I, J ) = matrix( I, J )
!>              10    CONTINUE
!>              20 CONTINUE
!>
!>           Unchanged on exit.
!>
!>  LDA    - INTEGER
!>           On entry, LDA specifies the first dimension of A as declared
!>           in the calling (sub) program. LDA must be at least
!>           ( k + 1 ).
!>           Unchanged on exit.
!>
!>  X      - COMPLEX array, dimension at least
!>           ( 1 + ( N - 1 )*abs( INCX ) ).
!>           Before entry, the incremented array X must contain the
!>           vector x.
!>           Unchanged on exit.
!>
!>  INCX   - INTEGER
!>           On entry, INCX specifies the increment for the elements of
!>           X. INCX must not be zero.
!>           Unchanged on exit.
!>
!>  BETA   - COMPLEX
!>           On entry, BETA specifies the scalar beta.
!>           Unchanged on exit.
!>
!>  Y      - COMPLEX array, dimension at least
!>           ( 1 + ( N - 1 )*abs( INCY ) ).
!>           Before entry, the incremented array Y must contain the
!>           vector y. On exit, Y is overwritten by the updated vector y.
!>
!>  INCY   - INTEGER
!>           On entry, INCY specifies the increment for the elements of
!>           Y. INCY must not be zero.
!>           Unchanged on exit.
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **150** of file **csbmv.f**.

## Author

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