SUBROUTINE SLATM1( MODE, COND, IRSIGN, IDIST, ISEED, D, N, INFO )
*
* -- LAPACK auxiliary test routine (version 3.1) --
* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd..
* November 2006
*
* .. Scalar Arguments ..
INTEGER IDIST, INFO, IRSIGN, MODE, N
REAL COND
* ..
* .. Array Arguments ..
INTEGER ISEED( 4 )
REAL D( * )
* ..
*
* Purpose
* =======
*
* SLATM1 computes the entries of D(1..N) as specified by
* MODE, COND and IRSIGN. IDIST and ISEED determine the generation
* of random numbers. SLATM1 is called by SLATMR to generate
* random test matrices for LAPACK programs.
*
* Arguments
* =========
*
* 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: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 - REAL
* 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 SLATM1
* to continue the same random number sequence.
* Changed on exit.
*
* D - REAL 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.
*
* 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
*
* =====================================================================
*
* .. Parameters ..
REAL ONE
PARAMETER ( ONE = 1.0E0 )
REAL HALF
PARAMETER ( HALF = 0.5E0 )
* ..
* .. Local Scalars ..
INTEGER I
REAL ALPHA, TEMP
* ..
* .. External Functions ..
REAL SLARAN
EXTERNAL SLARAN
* ..
* .. External Subroutines ..
EXTERNAL SLARNV, XERBLA
* ..
* .. Intrinsic Functions ..
INTRINSIC ABS, EXP, LOG, REAL
* ..
* .. Executable Statements ..
*
* Decode and Test the input parameters. Initialize flags & seed.
*
INFO = 0
*
* Quick return if possible
*
IF( N.EQ.0 )
$ RETURN
*
* Set INFO if an error
*
IF( MODE.LT.-6 .OR. MODE.GT.6 ) THEN
INFO = -1
ELSE IF( ( MODE.NE.-6 .AND. MODE.NE.0 .AND. MODE.NE.6 ) .AND.
$ ( IRSIGN.NE.0 .AND. IRSIGN.NE.1 ) ) THEN
INFO = -2
ELSE IF( ( MODE.NE.-6 .AND. MODE.NE.0 .AND. MODE.NE.6 ) .AND.
$ COND.LT.ONE ) THEN
INFO = -3
ELSE IF( ( MODE.EQ.6 .OR. MODE.EQ.-6 ) .AND.
$ ( IDIST.LT.1 .OR. IDIST.GT.3 ) ) THEN
INFO = -4
ELSE IF( N.LT.0 ) THEN
INFO = -7
END IF
*
IF( INFO.NE.0 ) THEN
CALL XERBLA( 'SLATM1', -INFO )
RETURN
END IF
*
* Compute D according to COND and MODE
*
IF( MODE.NE.0 ) THEN
GO TO ( 10, 30, 50, 70, 90, 110 )ABS( MODE )
*
* One large D value:
*
10 CONTINUE
DO 20 I = 1, N
D( I ) = ONE / COND
20 CONTINUE
D( 1 ) = ONE
GO TO 120
*
* One small D value:
*
30 CONTINUE
DO 40 I = 1, N
D( I ) = ONE
40 CONTINUE
D( N ) = ONE / COND
GO TO 120
*
* Exponentially distributed D values:
*
50 CONTINUE
D( 1 ) = ONE
IF( N.GT.1 ) THEN
ALPHA = COND**( -ONE / REAL( N-1 ) )
DO 60 I = 2, N
D( I ) = ALPHA**( I-1 )
60 CONTINUE
END IF
GO TO 120
*
* Arithmetically distributed D values:
*
70 CONTINUE
D( 1 ) = ONE
IF( N.GT.1 ) THEN
TEMP = ONE / COND
ALPHA = ( ONE-TEMP ) / REAL( N-1 )
DO 80 I = 2, N
D( I ) = REAL( N-I )*ALPHA + TEMP
80 CONTINUE
END IF
GO TO 120
*
* Randomly distributed D values on ( 1/COND , 1):
*
90 CONTINUE
ALPHA = LOG( ONE / COND )
DO 100 I = 1, N
D( I ) = EXP( ALPHA*SLARAN( ISEED ) )
100 CONTINUE
GO TO 120
*
* Randomly distributed D values from IDIST
*
110 CONTINUE
CALL SLARNV( IDIST, ISEED, N, D )
*
120 CONTINUE
*
* If MODE neither -6 nor 0 nor 6, and IRSIGN = 1, assign
* random signs to D
*
IF( ( MODE.NE.-6 .AND. MODE.NE.0 .AND. MODE.NE.6 ) .AND.
$ IRSIGN.EQ.1 ) THEN
DO 130 I = 1, N
TEMP = SLARAN( ISEED )
IF( TEMP.GT.HALF )
$ D( I ) = -D( I )
130 CONTINUE
END IF
*
* Reverse if MODE < 0
*
IF( MODE.LT.0 ) THEN
DO 140 I = 1, N / 2
TEMP = D( I )
D( I ) = D( N+1-I )
D( N+1-I ) = TEMP
140 CONTINUE
END IF
*
END IF
*
RETURN
*
* End of SLATM1
*
END