SLATM7
Craig Lucas, University of Manchester / NAG Ltd.
October, 2008
October, 2008
Purpose
SLATM7 computes the entries of D as specified by MODE
COND and IRSIGN. IDIST and ISEED determine the generation
of random numbers. SLATM7 is called by SLATMT to generate
random test matrices.
COND and IRSIGN. IDIST and ISEED determine the generation
of random numbers. SLATM7 is called by SLATMT to generate
random test matrices.
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: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 |
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 SLATM7 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.
|
| 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 |