PDRSCL(l)					      LAPACK auxiliary routine (version 1.5)						 PDRSCL(l)

NAME

       PDRSCL - multiplie an N-element real distributed vector sub( X ) by the real scalar 1/a

SYNOPSIS

       SUBROUTINE PDRSCL( N, SA, SX, IX, JX, DESCX, INCX )

	   INTEGER	  IX, INCX, JX, N

	   DOUBLE	  PRECISION SA

	   INTEGER	  DESCX( * )

	   DOUBLE	  PRECISION SX( * )

PURPOSE

       PDRSCL  multiplies an N-element real distributed vector sub( X ) by the real scalar 1/a. This is done without overflow or underflow as long
       as the final result sub( X )/a does not overflow or underflow.

       where sub( X ) denotes X(IX:IX+N-1,JX:JX), if INCX = 1,
			      X(IX:IX,JX:JX+N-1), if INCX = M_X.

       Notes
       =====

       Each global data object is described by an associated description vector.  This vector stores the information  required	to  establish  the
       mapping between an object element and its corresponding process and memory location.

       Let  A  be a generic term for any 2D block cyclicly distributed array.  Such a global array has an associated description vector descA.	In
       the following comments, the character _ should be read as "of the global array".

       NOTATION        STORED IN      EXPLANATION
       --------------- -------------- -------------------------------------- DT_A   (global) descA[ DT_ ]   The descriptor type.  In this case,
				      DT_A = 1.
       CTXT_A (global) descA[ CTXT_ ] The BLACS context handle, indicating
				      the BLACS process grid A is distribu-
				      ted over. The context itself is glo-
				      bal, but the handle (the integer
				      value) may vary.
       M_A    (global) descA[ M_ ]    The number of rows in the global
				      array A.
       N_A    (global) descA[ N_ ]    The number of columns in the global
				      array A.
       MB_A   (global) descA[ MB_ ]   The blocking factor used to distribu-
				      te the rows of the array.
       NB_A   (global) descA[ NB_ ]   The blocking factor used to distribu-
				      te the columns of the array.  RSRC_A (global) descA[ RSRC_ ] The process row over which the first
				      row of the array A is distributed.  CSRC_A (global) descA[ CSRC_ ] The process column over which the
				      first column of the array A is
				      distributed.
       LLD_A  (local)  descA[ LLD_ ]  The leading dimension of the local
				      array.  LLD_A >= MAX(1,LOCr(M_A)).

       Let K be the number of rows or columns of a distributed matrix, and assume that its process grid has dimension p x q.
       LOCr( K ) denotes the number of elements of K that a process would receive if K were distributed over the p processes of its  process  col-
       umn.
       Similarly,  LOCc(  K  )	denotes the number of elements of K that a process would receive if K were distributed over the q processes of its
       process row.
       The values of LOCr() and LOCc() may be determined via a call to the ScaLAPACK tool function, NUMROC:
	       LOCr( M ) = NUMROC( M, MB_A, MYROW, RSRC_A, NPROW ),
	       LOCc( N ) = NUMROC( N, NB_A, MYCOL, CSRC_A, NPCOL ).  An upper bound for these quantities may be computed by:
	       LOCr( M ) <= ceil( ceil(M/MB_A)/NPROW )*MB_A
	       LOCc( N ) <= ceil( ceil(N/NB_A)/NPCOL )*NB_A

       Because vectors may be seen as particular matrices, a distributed vector is considered to be a distributed matrix.

ARGUMENTS

       N       (global input) pointer to INTEGER
	       The number of components of the distributed vector sub( X ).  N >= 0.

       SA      (global input) DOUBLE PRECISION
	       The scalar a which is used to divide each component of sub( X ).  SA must be >= 0, or the subroutine will divide by zero.

       SX      (local input/local output) DOUBLE PRECISION array
	       containing the local pieces of a distributed matrix of dimension of at least ( (JX-1)*M_X + IX + ( N - 1 )*abs( INCX ) ) This array
	       contains the entries of the distributed vector sub( X ).

       IX      (global input) pointer to INTEGER
	       The global row index of the submatrix of the distributed matrix X to operate on.

       JX      (global input) pointer to INTEGER
	       The global column index of the submatrix of the distributed matrix X to operate on.

       DESCX   (global and local input) INTEGER array of dimension 8.
	       The array descriptor of the distributed matrix X.

       INCX    (global input) pointer to INTEGER
	       The global increment for the elements of X. Only two values of INCX are supported in this version, namely 1 and M_X.

LAPACK version 1.5						    12 May 1997 							 PDRSCL(l)