DGTHR(3)                MathKeisan SPARSE BLAS routine                DGTHR(3)



NAME
       DGTHR - Gather a vector into compressed form

SYNOPSIS
       SUBROUTINE DGTHR( NZ, Y, X, INDX )

         INTEGER          NZ, INDX

         DOUBLE PRECISION Y, X

PURPOSE
       Gather(copy)  the specified components of a vector stored in full-stor-
       age form into compressed form. If all nonzero components of Y appear in
       INDX, then DGTHR performs

                     x := y

       which is symbolized by

                X(I) = Y( INDX(I) )

                for I = 1, ..., NZ.


ARGUMENTS
       NZ      (input) INTEGER
               Number of elements in the compressed form.

       Y       (input) DOUBLE PRECISION
               Array,  on  input,  which contains the vector Y in full storage
               form. Only the elements corresponding to the  indices  in  INDX
               will be accessed.

       INDX    (input) INTEGER
               Array  containing the indices of the values to be gathered into
               compressed form.

       X       (output) DOUBLE PRECISION
               Array containing the values gathered into the compressed  form.

FURTHER DETAILS
       Sparse  BLAS  algorithm  is  from  ACM  algorithm  692 by D. Dodson, R.
       Grimes, and J. Lewis.


SEE ALSO
       sblas(3)



MathKeisan                         June 1991                          DGTHR(3)