---
name: "clatm1.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/clatm1.f"
---

# clatm1.f(3)

## NAME

TESTING/MATGEN/clatm1.f

## SYNOPSIS

### Functions/Subroutines

subroutine **clatm1** (mode, cond, irsign, idist, iseed, d, n, info)\
 **CLATM1**

## Function/Subroutine Documentation

### subroutine clatm1 (integer mode, real cond, integer irsign, integer idist, integer, dimension( 4 ) iseed, complex, dimension( \* ) d, integer n, integer info)

**CLATM1**

**Purpose:**

```
!>
!>    CLATM1 computes the entries of D(1..N) as specified by
!>    MODE, COND and IRSIGN. IDIST and ISEED determine the generation
!>    of random numbers. CLATM1 is called by CLATMR to generate
!>    random test matrices for LAPACK programs.
!>
```

**Parameters**

*MODE*

```
!>          MODE is INTEGER
!>           On entry describes how D is to be computed:
!>           MODE = 0 means do not change D.
!>           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 positive, D has entries ranging from
!>              1 to 1/COND, if negative, from 1/COND to 1,
!>           Not modified.
!>
```

*COND*

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

*IRSIGN*

```
!>          IRSIGN is INTEGER
!>           On entry, if MODE neither -6, 0 nor 6, determines sign of
!>           entries of D
!>           0 => leave entries of D unchanged
!>           1 => multiply each entry of D by random complex number
!>                uniformly distributed with absolute value 1
!>
```

*IDIST*

```
!>          IDIST is INTEGER
!>           On entry, IDIST specifies the type of distribution to be
!>           used to generate a random matrix .
!>           1 => real and imaginary parts each UNIFORM( 0, 1 )
!>           2 => real and imaginary parts each UNIFORM( -1, 1 )
!>           3 => real and imaginary parts each NORMAL( 0, 1 )
!>           4 => complex number uniform in DISK( 0, 1 )
!>           Not modified.
!>
```

*ISEED*

```
!>          ISEED is INTEGER array, dimension ( 4 )
!>           On entry ISEED specifies the seed of the random number
!>           generator. 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 CLATM1
!>           to continue the same random number sequence.
!>           Changed on exit.
!>
```

*D*

```
!>          D is COMPLEX array, dimension ( N )
!>           Array to be computed according to MODE, COND and IRSIGN.
!>           May be changed on exit if MODE is nonzero.
!>
```

*N*

```
!>          N is INTEGER
!>           Number of entries of D. Not modified.
!>
```

*INFO*

```
!>          INFO is INTEGER
!>            0  => normal termination
!>           -1  => if MODE not in range -6 to 6
!>           -2  => if MODE neither -6, 0 nor 6, and
!>                  IRSIGN neither 0 nor 1
!>           -3  => if MODE neither -6, 0 nor 6 and COND less than 1
!>           -4  => if MODE equals 6 or -6 and IDIST not in range 1 to 4
!>           -7  => if N negative
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **136** of file **clatm1.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.