ILAENV returns problem-dependent parameters for the local


 environment.  See ISPEC for a description of the parameters.


 In this version, the problem-dependent parameters are contained in


 the integer array IPARMS in the common block CLAENV and the value


 with index ISPEC is copied to ILAENV.  This version of ILAENV is


 to be used in conjunction with XLAENV in TESTING and TIMING.

ISPEC

          ISPEC is INTEGER


          Specifies the parameter to be returned as the value of


          ILAENV.


          = 1: the optimal blocksize; if this value is 1, an unblocked


               algorithm will give the best performance.


          = 2: the minimum block size for which the block routine


               should be used; if the usable block size is less than


               this value, an unblocked routine should be used.


          = 3: the crossover point (in a block routine, for N less


               than this value, an unblocked routine should be used)


          = 4: the number of shifts, used in the nonsymmetric


               eigenvalue routines


          = 5: the minimum column dimension for blocking to be used;


               rectangular blocks must have dimension at least k by m,


               where k is given by ILAENV(2,...) and m by ILAENV(5,...)


          = 6: the crossover point for the SVD (when reducing an m by n


               matrix to bidiagonal form, if max(m,n)/min(m,n) exceeds


               this value, a QR factorization is used first to reduce


               the matrix to a triangular form.)


          = 7: the number of processors


          = 8: the crossover point for the multishift QR and QZ methods


               for nonsymmetric eigenvalue problems.


          = 9: maximum size of the subproblems at the bottom of the


               computation tree in the divide-and-conquer algorithm


          =10: ieee NaN arithmetic can be trusted not to trap


          =11: infinity arithmetic can be trusted not to trap


          Other specifications (up to 100) can be added later.

NAME

          NAME is CHARACTER*(*)


          The name of the calling subroutine.

OPTS

          OPTS is CHARACTER*(*)


          The character options to the subroutine NAME, concatenated


          into a single character string.  For example, UPLO = 'U',


          TRANS = 'T', and DIAG = 'N' for a triangular routine would


          be specified as OPTS = 'UTN'.

N1

          N1 is INTEGER

N2

          N2 is INTEGER

N3

          N3 is INTEGER

N4

          N4 is INTEGER


          Problem dimensions for the subroutine NAME; these may not all


          be required.

ILAENV

          ILAENV is INTEGER


          >= 0: the value of the parameter specified by ISPEC


          < 0:  if ILAENV = -k, the k-th argument had an illegal value.

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  The following conventions have been used when calling ILAENV from the


  LAPACK routines:


  1)  OPTS is a concatenation of all of the character options to


      subroutine NAME, in the same order that they appear in the


      argument list for NAME, even if they are not used in determining


      the value of the parameter specified by ISPEC.


  2)  The problem dimensions N1, N2, N3, N4 are specified in the order


      that they appear in the argument list for NAME.  N1 is used


      first, N2 second, and so on, and unused problem dimensions are


      passed a value of -1.


  3)  The parameter value returned by ILAENV is checked for validity in


      the calling subroutine.  For example, ILAENV is used to retrieve


      the optimal blocksize for STRTRI as follows:


      NB = ILAENV( 1, 'STRTRI', UPLO // DIAG, N, -1, -1, -1 )


      IF( NB.LE.1 ) NB = MAX( 1, N )