TESTING/MATGEN/clatmt.f(3)

NAME
TESTING/MATGEN/clatmt.f

SYNOPSIS

  Functions/Subroutines
subroutine clatmt (m, n, dist, iseed, sym, d, mode, cond, dmax, rank, kl, ku, pack, a, lda, work, info)
CLATMT

Function/Subroutine Documentation

  subroutine clatmt (integer m, integer n, character dist, integer, dimension( 4 ) iseed, character sym, real, dimension( * ) d, integer mode, real cond, real dmax, integer rank, integer kl, integer ku, character pack, complex, dimension( lda, * ) a, integer lda, complex, dimension( * ) work, integer info)

CLATMT

Purpose:

        CLATMT generates random matrices with specified singular values
        (or hermitian with specified eigenvalues)
        for testing LAPACK programs.
        CLATMT operates by applying the following sequence of
        operations:
          Set the diagonal to D, where D may be input or
             computed according to MODE, COND, DMAX, and SYM
             as described below.
          Generate a matrix with the appropriate band structure, by one
             of two methods:
          Method A:
              Generate a dense M x N matrix by multiplying D on the left
                  and the right by random unitary matrices, then:
              Reduce the bandwidth according to KL and KU, using
                  Householder transformations.
          Method B:
              Convert the bandwidth-0 (i.e., diagonal) matrix to a
                  bandwidth-1 matrix using Givens rotations, 'chasing'
                  out-of-band elements back, much as in QR; then convert
                  the bandwidth-1 to a bandwidth-2 matrix, etc.  Note
                  that for reasonably small bandwidths (relative to M and
                  N) this requires less storage, as a dense matrix is not
                  generated.  Also, for hermitian or symmetric matrices,
                  only one triangle is generated.
          Method A is chosen if the bandwidth is a large fraction of the
              order of the matrix, and LDA is at least M (so a dense
              matrix can be stored.)  Method B is chosen if the bandwidth
              is small (< 1/2 N for hermitian or symmetric, < .3 N+M for
              non-symmetric), or LDA is less than M and not less than the
              bandwidth.
          Pack the matrix if desired. Options specified by PACK are:
             no packing
             zero out upper half (if hermitian)
             zero out lower half (if hermitian)
             store the upper half columnwise (if hermitian or upper
                   triangular)
             store the lower half columnwise (if hermitian or lower
                   triangular)
             store the lower triangle in banded format (if hermitian or
                   lower triangular)
             store the upper triangle in banded format (if hermitian or
                   upper triangular)
             store the entire matrix in banded format
          If Method B is chosen, and band format is specified, then the
             matrix will be generated in the band format, so no repacking
             will be necessary.

Parameters
    M

              M is INTEGER
               The number of rows of A. Not modified.

    N

              N is INTEGER
               The number of columns of A. N must equal M if the matrix
               is symmetric or hermitian (i.e., if SYM is not 'N')
               Not modified.

    DIST

              DIST is CHARACTER*1
               On entry, DIST specifies the type of distribution to be used
               to generate the random eigen-/singular values.
               'U' => UNIFORM( 0, 1 )  ( 'U' for uniform )
               'S' => UNIFORM( -1, 1 ) ( 'S' for symmetric )
               'N' => NORMAL( 0, 1 )   ( 'N' for normal )
               Not modified.

    ISEED

              ISEED is INTEGER array, dimension ( 4 )
               On entry ISEED specifies the seed of the random number
               generator. They should lie between 0 and 4095 inclusive,
               and ISEED(4) should be odd. 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 CLATMT
               to continue the same random number sequence.
               Changed on exit.

    SYM

              SYM is CHARACTER*1
               If SYM='H', the generated matrix is hermitian, with
                 eigenvalues specified by D, COND, MODE, and DMAX; they
                 may be positive, negative, or zero.
               If SYM='P', the generated matrix is hermitian, with
                 eigenvalues (= singular values) specified by D, COND,
                 MODE, and DMAX; they will not be negative.
               If SYM='N', the generated matrix is nonsymmetric, with
                 singular values specified by D, COND, MODE, and DMAX;
                 they will not be negative.
               If SYM='S', the generated matrix is (complex) symmetric,
                 with singular values specified by D, COND, MODE, and
                 DMAX; they will not be negative.
               Not modified.

    D

              D is REAL array, dimension ( MIN( M, N ) )
               This array is used to specify the singular values or
               eigenvalues of A (see SYM, above.)  If MODE=0, then D is
               assumed to contain the singular/eigenvalues, otherwise
               they will be computed according to MODE, COND, and DMAX,
               and placed in D.
               Modified if MODE is nonzero.

    MODE

              MODE is INTEGER
               On entry this describes how the singular/eigenvalues are to
               be specified:
               MODE = 0 means use D as input
               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))
               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,
               If SYM='H', and MODE is neither 0, 6, nor -6, then
                  the elements of D will also be multiplied by a random
                  sign (i.e., +1 or -1.)
               Not modified.

    COND

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

    DMAX

              DMAX is REAL
               If MODE is neither -6, 0 nor 6, the contents of D, as
               computed according to MODE and COND, will be scaled by
               DMAX / max(abs(D(i))); thus, the maximum absolute eigen- or
               singular value (which is to say the norm) will be abs(DMAX).
               Note that DMAX need not be positive: if DMAX is negative
               (or zero), D will be scaled by a negative number (or zero).
               Not modified.

    RANK

              RANK is INTEGER
               The rank of matrix to be generated for modes 1,2,3 only.
               D( RANK+1:N ) = 0.
               Not modified.

    KL

              KL is INTEGER
               This specifies the lower bandwidth of the  matrix. For
               example, KL=0 implies upper triangular, KL=1 implies upper
               Hessenberg, and KL being at least M-1 means that the matrix
               has full lower bandwidth.  KL must equal KU if the matrix
               is symmetric or hermitian.
               Not modified.

    KU

              KU is INTEGER
               This specifies the upper bandwidth of the  matrix. For
               example, KU=0 implies lower triangular, KU=1 implies lower
               Hessenberg, and KU being at least N-1 means that the matrix
               has full upper bandwidth.  KL must equal KU if the matrix
               is symmetric or hermitian.
               Not modified.

    PACK

              PACK is CHARACTER*1
               This specifies packing of matrix as follows:
               'N' => no packing
               'U' => zero out all subdiagonal entries (if symmetric
                      or hermitian)
               'L' => zero out all superdiagonal entries (if symmetric
                      or hermitian)
               'C' => store the upper triangle columnwise (only if the
                      matrix is symmetric, hermitian, or upper triangular)
               'R' => store the lower triangle columnwise (only if the
                      matrix is symmetric, hermitian, or lower triangular)
               'B' => store the lower triangle in band storage scheme
                      (only if the matrix is symmetric, hermitian, or
                      lower triangular)
               'Q' => store the upper triangle in band storage scheme
                      (only if the matrix is symmetric, hermitian, or
                      upper triangular)
               'Z' => store the entire matrix in band storage scheme
                          (pivoting can be provided for by using this
                          option to store A in the trailing rows of
                          the allocated storage)
               Using these options, the various LAPACK packed and banded
               storage schemes can be obtained:
               GB                    - use 'Z'
               PB, SB, HB, or TB     - use 'B' or 'Q'
               PP, SP, HB, or TP     - use 'C' or 'R'
               If two calls to CLATMT differ only in the PACK parameter,
               they will generate mathematically equivalent matrices.
               Not modified.

    A

              A is COMPLEX array, dimension ( LDA, N )
               On exit A is the desired test matrix.  A is first generated
               in full (unpacked) form, and then packed, if so specified
               by PACK.  Thus, the first M elements of the first N
               columns will always be modified.  If PACK specifies a
               packed or banded storage scheme, all LDA elements of the
               first N columns will be modified; the elements of the
               array which do not correspond to elements of the generated
               matrix are set to zero.
               Modified.

    LDA

              LDA is INTEGER
               LDA specifies the first dimension of A as declared in the
               calling program.  If PACK='N', 'U', 'L', 'C', or 'R', then
               LDA must be at least M.  If PACK='B' or 'Q', then LDA must
               be at least MIN( KL, M-1) (which is equal to MIN(KU,N-1)).
               If PACK='Z', LDA must be large enough to hold the packed
               array: MIN( KU, N-1) + MIN( KL, M-1) + 1.
               Not modified.

    WORK

              WORK is COMPLEX array, dimension ( 3*MAX( N, M ) )
               Workspace.
               Modified.

    INFO

              INFO is INTEGER
               Error code.  On exit, INFO will be set to one of the
               following values:
                 0 => normal return
                -1 => M negative or unequal to N and SYM='S', 'H', or 'P'
                -2 => N negative
                -3 => DIST illegal string
                -5 => SYM illegal string
                -7 => MODE not in range -6 to 6
                -8 => COND less than 1.0, and MODE neither -6, 0 nor 6
               -10 => KL negative
               -11 => KU negative, or SYM is not 'N' and KU is not equal to
                      KL
               -12 => PACK illegal string, or PACK='U' or 'L', and SYM='N';
                      or PACK='C' or 'Q' and SYM='N' and KL is not zero;
                      or PACK='R' or 'B' and SYM='N' and KU is not zero;
                      or PACK='U', 'L', 'C', 'R', 'B', or 'Q', and M is not
                      N.
               -14 => LDA is less than M, or PACK='Z' and LDA is less than
                      MIN(KU,N-1) + MIN(KL,M-1) + 1.
                1  => Error return from SLATM7
                2  => Cannot scale to DMAX (max. sing. value is 0)
                3  => Error return from CLAGGE, CLAGHE or CLAGSY

Author
    Univ. of Tennessee

    Univ. of California Berkeley

    Univ. of Colorado Denver

    NAG Ltd.

Definition at line 338 of file clatmt.f.

Author

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