---
name: "claqsb.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/claqsb.f"
---

# claqsb.f(3)

## NAME

SRC/claqsb.f

## SYNOPSIS

### Functions/Subroutines

subroutine **claqsb** (uplo, n, kd, ab, ldab, s, scond, amax, equed)\
 **CLAQSB** scales a symmetric/Hermitian band matrix, using scaling factors computed by spbequ.

## Function/Subroutine Documentation

### subroutine claqsb (character uplo, integer n, integer kd, complex, dimension( ldab, \* ) ab, integer ldab, real, dimension( \* ) s, real scond, real amax, character equed)

**CLAQSB** scales a symmetric/Hermitian band matrix, using scaling factors computed by spbequ.

**Purpose:**

```
!>
!> CLAQSB equilibrates a symmetric band matrix A using the scaling
!> factors in the vector S.
!>
```

**Parameters**

*UPLO*

```
!>          UPLO is CHARACTER*1
!>          Specifies whether the upper or lower triangular part of the
!>          symmetric matrix A is stored.
!>          = 'U':  Upper triangular
!>          = 'L':  Lower triangular
!>
```

*N*

```
!>          N is INTEGER
!>          The order of the matrix A.  N >= 0.
!>
```

*KD*

```
!>          KD is INTEGER
!>          The number of super-diagonals of the matrix A if UPLO = 'U',
!>          or the number of sub-diagonals if UPLO = 'L'.  KD >= 0.
!>
```

*AB*

```
!>          AB is COMPLEX 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
!>          Cholesky factorization A = U**H *U or A = L*L**H of the band
!>          matrix A, in the same storage format as A.
!>
```

*LDAB*

```
!>          LDAB is INTEGER
!>          The leading dimension of the array AB.  LDAB >= KD+1.
!>
```

*S*

```
!>          S is REAL array, dimension (N)
!>          The scale factors for A.
!>
```

*SCOND*

```
!>          SCOND is REAL
!>          Ratio of the smallest S(i) to the largest S(i).
!>
```

*AMAX*

```
!>          AMAX is REAL
!>          Absolute value of largest matrix entry.
!>
```

*EQUED*

```
!>          EQUED is CHARACTER*1
!>          Specifies whether or not equilibration was done.
!>          = 'N':  No equilibration.
!>          = 'Y':  Equilibration was done, i.e., A has been replaced by
!>                  diag(S) * A * diag(S).
!>
```

**Internal Parameters:**

```
!>  THRESH is a threshold value used to decide if scaling should be done
!>  based on the ratio of the scaling factors.  If SCOND < THRESH,
!>  scaling is done.
!>
!>  LARGE and SMALL are threshold values used to decide if scaling should
!>  be done based on the absolute size of the largest matrix element.
!>  If AMAX > LARGE or AMAX < SMALL, scaling is done.
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **140** of file **claqsb.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.