---
name: "zlatme.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/zlatme.f"
---

# zlatme.f(3)

## NAME

TESTING/MATGEN/zlatme.f

## SYNOPSIS

### Functions/Subroutines

subroutine **zlatme** (n, dist, iseed, d, mode, cond, dmax, rsign, upper, sim, ds, modes, conds, kl, ku, anorm, a, lda, work, info)\
 **ZLATME**

## Function/Subroutine Documentation

### subroutine zlatme (integer n, character dist, integer, dimension( 4 ) iseed, complex\*16, dimension( \* ) d, integer mode, double precision cond, complex\*16 dmax, character rsign, character upper, character sim, double precision, dimension( \* ) ds, integer modes, double precision conds, integer kl, integer ku, double precision anorm, complex\*16, dimension( lda, \* ) a, integer lda, complex\*16, dimension( \* ) work, integer info)

**ZLATME**

**Purpose:**

```
!>
!>    ZLATME generates random non-symmetric square matrices with
!>    specified eigenvalues for testing LAPACK programs.
!>
!>    ZLATME operates by applying the following sequence of
!>    operations:
!>
!>    1. Set the diagonal to D, where D may be input or
!>         computed according to MODE, COND, DMAX, and RSIGN
!>         as described below.
!>
!>    2. If UPPER='T', the upper triangle of A is set to random values
!>         out of distribution DIST.
!>
!>    3. If SIM='T', A is multiplied on the left by a random matrix
!>         X, whose singular values are specified by DS, MODES, and
!>         CONDS, and on the right by X inverse.
!>
!>    4. If KL < N-1, the lower bandwidth is reduced to KL using
!>         Householder transformations.  If KU < N-1, the upper
!>         bandwidth is reduced to KU.
!>
!>    5. If ANORM is not negative, the matrix is scaled to have
!>         maximum-element-norm ANORM.
!>
!>    (Note: since the matrix cannot be reduced beyond Hessenberg form,
!>     no packing options are available.)
!>
```

**Parameters**

*N*

```
!>          N is INTEGER
!>           The number of columns (or rows) of A. Not modified.
!>
```

*DIST*

```
!>          DIST is CHARACTER*1
!>           On entry, DIST specifies the type of distribution to be used
!>           to generate the random eigen-/singular values, and on the
!>           upper triangle (see UPPER).
!>           'U' => UNIFORM( 0, 1 )  ( 'U' for uniform )
!>           'S' => UNIFORM( -1, 1 ) ( 'S' for symmetric )
!>           'N' => NORMAL( 0, 1 )   ( 'N' for normal )
!>           'D' => uniform on the complex disc |z| < 1.
!>           Not modified.
!>
```

*ISEED*

```
!>          ISEED is INTEGER array, dimension ( 4 )
!>           On entry ISEED specifies the seed of the random number
!>           generator. They should lie between 0 and 4095 inclusive,
!>           and ISEED(4) should be odd. The random number generator
!>           uses a linear congruential sequence limited to small
!>           integers, and so should produce machine independent
!>           random numbers. The values of ISEED are changed on
!>           exit, and can be used in the next call to ZLATME
!>           to continue the same random number sequence.
!>           Changed on exit.
!>
```

*D*

```
!>          D is COMPLEX*16 array, dimension ( N )
!>           This array is used to specify the eigenvalues of A.  If
!>           MODE=0, then D is assumed to contain the eigenvalues
!>           otherwise they will be computed according to MODE, COND,
!>           DMAX, and RSIGN and placed in D.
!>           Modified if MODE is nonzero.
!>
```

*MODE*

```
!>          MODE is INTEGER
!>           On entry this describes how the eigenvalues are to
!>           be specified:
!>           MODE = 0 means use D as input
!>           MODE = 1 sets D(1)=1 and D(2:N)=1.0/COND
!>           MODE = 2 sets D(1:N-1)=1 and D(N)=1.0/COND
!>           MODE = 3 sets D(I)=COND**(-(I-1)/(N-1))
!>           MODE = 4 sets D(i)=1 - (i-1)/(N-1)*(1 - 1/COND)
!>           MODE = 5 sets D to random numbers in the range
!>                    ( 1/COND , 1 ) such that their logarithms
!>                    are uniformly distributed.
!>           MODE = 6 set D to random numbers from same distribution
!>                    as the rest of the matrix.
!>           MODE < 0 has the same meaning as ABS(MODE), except that
!>              the order of the elements of D is reversed.
!>           Thus if MODE is between 1 and 4, D has entries ranging
!>              from 1 to 1/COND, if between -1 and -4, D has entries
!>              ranging from 1/COND to 1,
!>           Not modified.
!>
```

*COND*

```
!>          COND is DOUBLE PRECISION
!>           On entry, this is used as described under MODE above.
!>           If used, it must be >= 1. Not modified.
!>
```

*DMAX*

```
!>          DMAX is COMPLEX*16
!>           If MODE is neither -6, 0 nor 6, the contents of D, as
!>           computed according to MODE and COND, will be scaled by
!>           DMAX / max(abs(D(i))).  Note that DMAX need not be
!>           positive or real: if DMAX is negative or complex (or zero),
!>           D will be scaled by a negative or complex number (or zero).
!>           If RSIGN='F' then the largest (absolute) eigenvalue will be
!>           equal to DMAX.
!>           Not modified.
!>
```

*RSIGN*

```
!>          RSIGN is CHARACTER*1
!>           If MODE is not 0, 6, or -6, and RSIGN='T', then the
!>           elements of D, as computed according to MODE and COND, will
!>           be multiplied by a random complex number from the unit
!>           circle |z| = 1.  If RSIGN='F', they will not be.  RSIGN may
!>           only have the values 'T' or 'F'.
!>           Not modified.
!>
```

*UPPER*

```
!>          UPPER is CHARACTER*1
!>           If UPPER='T', then the elements of A above the diagonal
!>           will be set to random numbers out of DIST.  If UPPER='F',
!>           they will not.  UPPER may only have the values 'T' or 'F'.
!>           Not modified.
!>
```

*SIM*

```
!>          SIM is CHARACTER*1
!>           If SIM='T', then A will be operated on by a , i.e., multiplied on the left by a matrix X and
!>           on the right by X inverse.  X = U S V, where U and V are
!>           random unitary matrices and S is a (diagonal) matrix of
!>           singular values specified by DS, MODES, and CONDS.  If
!>           SIM='F', then A will not be transformed.
!>           Not modified.
!>
```

*DS*

```
!>          DS is DOUBLE PRECISION array, dimension ( N )
!>           This array is used to specify the singular values of X,
!>           in the same way that D specifies the eigenvalues of A.
!>           If MODE=0, the DS contains the singular values, which
!>           may not be zero.
!>           Modified if MODE is nonzero.
!>
```

*MODES*

```
!>          MODES is INTEGER
!>
```

*CONDS*

```
!>          CONDS is DOUBLE PRECISION
!>           Similar to MODE and COND, but for specifying the diagonal
!>           of S.  MODES=-6 and +6 are not allowed (since they would
!>           result in randomly ill-conditioned eigenvalues.)
!>
```

*KL*

```
!>          KL is INTEGER
!>           This specifies the lower bandwidth of the  matrix.  KL=1
!>           specifies upper Hessenberg form.  If KL is at least N-1,
!>           then A will have full lower bandwidth.
!>           Not modified.
!>
```

*KU*

```
!>          KU is INTEGER
!>           This specifies the upper bandwidth of the  matrix.  KU=1
!>           specifies lower Hessenberg form.  If KU is at least N-1,
!>           then A will have full upper bandwidth; if KU and KL
!>           are both at least N-1, then A will be dense.  Only one of
!>           KU and KL may be less than N-1.
!>           Not modified.
!>
```

*ANORM*

```
!>          ANORM is DOUBLE PRECISION
!>           If ANORM is not negative, then A will be scaled by a non-
!>           negative real number to make the maximum-element-norm of A
!>           to be ANORM.
!>           Not modified.
!>
```

*A*

```
!>          A is COMPLEX*16 array, dimension ( LDA, N )
!>           On exit A is the desired test matrix.
!>           Modified.
!>
```

*LDA*

```
!>          LDA is INTEGER
!>           LDA specifies the first dimension of A as declared in the
!>           calling program.  LDA must be at least M.
!>           Not modified.
!>
```

*WORK*

```
!>          WORK is COMPLEX*16 array, dimension ( 3*N )
!>           Workspace.
!>           Modified.
!>
```

*INFO*

```
!>          INFO is INTEGER
!>           Error code.  On exit, INFO will be set to one of the
!>           following values:
!>             0 => normal return
!>            -1 => N negative
!>            -2 => DIST illegal string
!>            -5 => MODE not in range -6 to 6
!>            -6 => COND less than 1.0, and MODE neither -6, 0 nor 6
!>            -9 => RSIGN is not 'T' or 'F'
!>           -10 => UPPER is not 'T' or 'F'
!>           -11 => SIM   is not 'T' or 'F'
!>           -12 => MODES=0 and DS has a zero singular value.
!>           -13 => MODES is not in the range -5 to 5.
!>           -14 => MODES is nonzero and CONDS is less than 1.
!>           -15 => KL is less than 1.
!>           -16 => KU is less than 1, or KL and KU are both less than
!>                  N-1.
!>           -19 => LDA is less than M.
!>            1  => Error return from ZLATM1 (computing D)
!>            2  => Cannot scale to DMAX (max. eigenvalue is 0)
!>            3  => Error return from DLATM1 (computing DS)
!>            4  => Error return from ZLARGE
!>            5  => Zero singular value from DLATM1.
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **296** of file **zlatme.f**.

## Author

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