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DLAMSH(l)			       )			     DLAMSH(l)

NAME
       DLAMSH  -  send multiple	shifts through a small (single node) matrix to
       see how consecutive small subdiagonal elements are modified  by	subse-
       quent  shifts in	an effort to maximize the number of bulges that	can be
       sent through

SYNOPSIS
       SUBROUTINE DLAMSH ( S, LDS, NBULGE, JBLK, H, LDH, N, ULP	)

	   INTEGER	 LDS, NBULGE, JBLK, LDH, N

	   DOUBLE	 PRECISION ULP

	   DOUBLE	 PRECISION S(LDS,*), H(LDH,*)

PURPOSE
       DLAMSH sends multiple shifts through a small (single  node)  matrix  to
       see  how	 consecutive small subdiagonal elements	are modified by	subse-
       quent shifts in an effort to maximize the number	of bulges that can  be
       sent  through.  DLAMSH  should  only  be	called when there are multiple
       shifts/bulges
	  (NBULGE > 1) and the first shift is starting in the middle of	an
	  unreduced Hessenberg matrix because of two or	more consecutive small
	  subdiagonal elements.

ARGUMENTS
       S       (local input/output) DOUBLE PRECISION array, (LDS,*)
	       On entry, the matrix of shifts.	Only the 2x2 diagonal of S  is
	       referenced.   It	is assumed that	S has JBLK double shifts (size
	       2).  On exit, the data is rearranged in the best	order for  ap-
	       plying.

       LDS     (local input) INTEGER
	       On  entry, the leading dimension	of S.  Unchanged on exit.  1 <
	       NBULGE <= JBLK <= LDS/2

       NBULGE  (local input/output) INTEGER
	       On entry, the number of bulges  to  send	 through  H  (	>1  ).
	       NBULGE  should be less than the maximum determined (JBLK).  1 <
	       NBULGE <= JBLK <= LDS/2 On exit,	the maximum number  of	bulges
	       that can	be sent	through.

       JBLK    (local input) INTEGER
	       On  entry, the number of	shifts determined for S.  Unchanged on
	       exit.

       H       (local input/output) DOUBLE PRECISION array (LDH,N)
	       On entry, the local matrix to apply the shifts on.  H should be
	       aligned	so  that  the starting row is 2.  On exit, the data is
	       destroyed.

       LDS     (local input) INTEGER
	       On entry, the leading dimension of S.  Unchanged	on exit.

       N       (local input) INTEGER
	       On entry, the size of H.	 If all	the bulges are expected	to  go
	       through,	 N  should  be at least	4*NBULGE+2.  Otherwise,	NBULGE
	       may be reduced by this routine.

       ULP     (local input) DOUBLE PRECISION
	       On entry, machine precision Unchanged on	exit.

	       Implemented by:	G. Henry, May 1, 1997

ScaLAPACK version 1.7		13 August 2001			     DLAMSH(l)

NAME | SYNOPSIS | PURPOSE | ARGUMENTS

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