---
name: "dlatm7.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/dlatm7.f"
---

# dlatm7.f(3)

## NAME

TESTING/MATGEN/dlatm7.f

## SYNOPSIS

### Functions/Subroutines

subroutine **dlatm7** (mode, cond, irsign, idist, iseed, d, n, rank, info)\
 **DLATM7**

## Function/Subroutine Documentation

### subroutine dlatm7 (integer mode, double precision cond, integer irsign, integer idist, integer, dimension( 4 ) iseed, double precision, dimension( \* ) d, integer n, integer rank, integer info)

**DLATM7**

**Purpose:**

```
!>
!>    DLATM7 computes the entries of D as specified by MODE
!>    COND and IRSIGN. IDIST and ISEED determine the generation
!>    of random numbers. DLATM7 is called by DLATMT to generate
!>    random test matrices.
!>
```

```
!>  MODE   - 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:RANK)=1.0/COND
!>           MODE = 2 sets D(1:RANK-1)=1 and D(RANK)=1.0/COND
!>           MODE = 3 sets D(I)=COND**(-(I-1)/(RANK-1)) I=1:RANK
!>
!>           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   - DOUBLE PRECISION
!>           On entry, used as described under MODE above.
!>           If used, it must be >= 1. Not modified.
!>
!>  IRSIGN - 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 1 or -1 with probability .5
!>
!>  IDIST  - CHARACTER*1
!>           On entry, IDIST specifies the type of distribution to be
!>           used to generate a random matrix .
!>           1 => UNIFORM( 0, 1 )
!>           2 => UNIFORM( -1, 1 )
!>           3 => NORMAL( 0, 1 )
!>           Not modified.
!>
!>  ISEED  - 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 DLATM7
!>           to continue the same random number sequence.
!>           Changed on exit.
!>
!>  D      - DOUBLE PRECISION array, dimension ( MIN( M , N ) )
!>           Array to be computed according to MODE, COND and IRSIGN.
!>           May be changed on exit if MODE is nonzero.
!>
!>  N      - INTEGER
!>           Number of entries of D. Not modified.
!>
!>  RANK   - INTEGER
!>           The rank of matrix to be generated for modes 1,2,3 only.
!>           D( RANK+1:N ) = 0.
!>           Not modified.
!>
!>  INFO   - 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 3
!>           -7  => if N negative
!>
```

**Author**

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **120** of file **dlatm7.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.