*nix Documentation Project
·  Home
 +   man pages
·  Linux HOWTOs
·  FreeBSD Tips
·  *niX Forums

  man pages->IRIX man pages -> complib/ilaenv (3)              
Title
Content
Arch
Section
 

Contents


ILAENV(3F)							    ILAENV(3F)


NAME    [Toc]    [Back]

     ILAENV - i	called from the	LAPACK routines	to choose problem-dependent
     parameters	for the	local environment

SYNOPSIS    [Toc]    [Back]

     INTEGER FUNCTION ILAENV( ISPEC, NAME, OPTS, N1, N2, N3, N4	)

	 CHARACTER*(  *	) NAME,	OPTS

	 INTEGER      ISPEC, N1, N2, N3, N4

PURPOSE    [Toc]    [Back]

     ILAENV is called from the LAPACK routines to choose problem-dependent
     parameters	for the	local environment.  See	ISPEC for a description	of the
     parameters.

     This version provides a set of parameters which should give good, but not
     optimal, performance on many of the currently available computers.	 Users
     are encouraged to modify this subroutine to set the tuning	parameters for
     their particular machine using the	option and problem size	information in
     the arguments.

     This routine will not function correctly if it is converted to all	lower
     case.  Converting it to all upper case is allowed.

ARGUMENTS    [Toc]    [Back]

     ISPEC   (input) 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.

     NAME    (input) CHARACTER*(*)
	     The name of the calling subroutine, in either upper case or lower
	     case.






									Page 1






ILAENV(3F)							    ILAENV(3F)



     OPTS    (input) 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	     (input) INTEGER
	     N2	     (input) INTEGER N3	     (input) INTEGER N4	     (input)
	     INTEGER Problem dimensions	for the	subroutine NAME; these may not
	     all be required.

	     >=	0: the value of	the parameter specified	by ISPEC < 0:  if
	     ILAENV = -k, the k-th argument had	an illegal value.

FURTHER	DETAILS
     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 )
ILAENV(3F)							    ILAENV(3F)


NAME    [Toc]    [Back]

     ILAENV - i	called from the	LAPACK routines	to choose problem-dependent
     parameters	for the	local environment

SYNOPSIS    [Toc]    [Back]

     INTEGER FUNCTION ILAENV( ISPEC, NAME, OPTS, N1, N2, N3, N4	)

	 CHARACTER*(  *	) NAME,	OPTS

	 INTEGER      ISPEC, N1, N2, N3, N4

PURPOSE    [Toc]    [Back]

     ILAENV is called from the LAPACK routines to choose problem-dependent
     parameters	for the	local environment.  See	ISPEC for a description	of the
     parameters.

     This version provides a set of parameters which should give good, but not
     optimal, performance on many of the currently available computers.	 Users
     are encouraged to modify this subroutine to set the tuning	parameters for
     their particular machine using the	option and problem size	information in
     the arguments.

     This routine will not function correctly if it is converted to all	lower
     case.  Converting it to all upper case is allowed.

ARGUMENTS    [Toc]    [Back]

     ISPEC   (input) 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.

     NAME    (input) CHARACTER*(*)
	     The name of the calling subroutine, in either upper case or lower
	     case.






									Page 1






ILAENV(3F)							    ILAENV(3F)



     OPTS    (input) 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	     (input) INTEGER
	     N2	     (input) INTEGER N3	     (input) INTEGER N4	     (input)
	     INTEGER Problem dimensions	for the	subroutine NAME; these may not
	     all be required.

	     >=	0: the value of	the parameter specified	by ISPEC < 0:  if
	     ILAENV = -k, the k-th argument had	an illegal value.

FURTHER	DETAILS
     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 )


									PPPPaaaaggggeeee 2222
[ Back ]
 Similar pages
Name OS Title
xerbla IRIX i an error handler for the LAPACK routines
localeconv Tru64 Retrieve locale-dependent formatting parameters
glTexEnviv Tru64 set texture environment parameters
glTexEnvfv Tru64 set texture environment parameters
glTexEnvf Tru64 set texture environment parameters
glTexEnv Tru64 set texture environment parameters
gltexenv IRIX set texture environment parameters
glTexEnvi Tru64 set texture environment parameters
glGetTexEnviv Tru64 return texture environment parameters
glgettexenv IRIX return texture environment parameters
Copyright © 2004-2005 DeniX Solutions SRL
newsletter delivery service