# dlatm1.f - Man Page

TESTING/MATGEN/dlatm1.f

## Synopsis

### Functions/Subroutines

subroutine **dlatm1** (mode, cond, irsign, idist, iseed, d, n, info)**DLATM1**

## Function/Subroutine Documentation

### subroutine dlatm1 (integer mode, double precision cond, integer irsign, integer idist, integer, dimension( 4 ) iseed, double precision, dimension( * ) d, integer n, integer info)

**DLATM1**

**Purpose:**

DLATM1 computes the entries of D(1..N) as specified by MODE, COND and IRSIGN. IDIST and ISEED determine the generation of random numbers. DLATM1 is called by DLATMR 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 DOUBLE PRECISION 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 1 or -1 with probability .5

*IDIST*IDIST is INTEGER 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*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 DLATM1 to continue the same random number sequence. Changed on exit.

*D*D is DOUBLE PRECISION 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 3 -7 => if N negative

**Author**Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Definition at line **134** of file **dlatm1.f**.

## Author

Generated automatically by Doxygen for LAPACK from the source code.

## Referenced By

The man page dlatm1(3) is an alias of dlatm1.f(3).

Tue Nov 28 2023 12:08:43 Version 3.12.0 LAPACK