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sc::FileGrp(3)			     MPQC			sc::FileGrp(3)

NAME
       sc::FileGrp - The FileGrp abstract class	provides a way of accessing
       distributed file	in a parallel machine.

SYNOPSIS
       #include	<file.h>

       Inherits	sc::DescribedClass.

       Inherited by sc::ProcFileGrp.

   Public Member Functions
       FileGrp (const Ref< KeyVal > &)
       void open ()
	   Opens the files.
       void close ()
	   Closes the files.
       void set_filename (char *name)
	   Sets	the filename for the FileGrp.
       const char * get_filename () const
	   Returns the filename	for the	FileGrp.
       int me () const
	   Returns who I am.
       int n ()	const
	   Returns how many nodes there	are.
       virtual void set_localsize (size_t)=0
	   Set the size	of locally held	data.
       size_t localsize	()
	   Returns the amount of data residing locally on me().
       distsize_t localoffset ()
	   Returns the global offset to	this node's data.
       int size	(int node)
	   Returns the amount of data residing on node.
       distsize_t offset (int node)
	   Returns the global offset to	node's data.
       distsize_t totalsize ()
	   Returns the sum of all data allocated on all	nodes.
       virtual void activate ()
	   Activate is called before the data is to be used.
       virtual void deactivate ()
	   Deactivate is called	after the data has been	used.
       virtual void * obtain_writeonly (distsize_t offset, int size)=0
	   This	gives write access to the data location. No locking is done.
       virtual void * obtain_readwrite (distsize_t offset, int size)=0
	   Only	one thread can have an unreleased obtain_readwrite at a	time.
       virtual void * obtain_readonly (distsize_t offset, int size)=0
	   This	gives read access to the file location.	No locking is done.
       virtual void release_readonly (void *data, distsize_t offset, int
	   size)=0
	   This	is called when read access is no longer	needed.
       virtual void release_writeonly (void *data, distsize_t offset, int
	   size)=0
	   This	is called when write access is no longer needed.
       virtual void release_readwrite (void *data, distsize_t offset, int
	   size)=0
	   This	is called when read/write access is no longer needed.
       virtual void sum_reduction (double *data, distsize_t doffset, int
	   dsize)
       virtual void sum_reduction_on_node (double *data, size_t	doffset, int
	   dsize, int node=-1)
       virtual void sync ()=0
	   Synchronizes	all the	nodes.
       virtual void catchup ()
	   Processes outstanding requests.
       virtual void print (std::ostream	&o=ExEnv::out0()) const
	   Prints out information about	the object.
       virtual FileGrp * clone ()=0
	   Clones the given FileGrp. The new FileGrp may need to be
	   initialized additionally.

   Static Public Member	Functions
       static FileGrp *	initial_filegrp	(int &argc, char **argv)
	   Create a file group.
       static FileGrp *	initial_filegrp	()
       static void set_default_filegrp (const Ref< FileGrp > &)
	   The default file group contains the primary file group to be	used
	   by an application.
       static FileGrp *	get_default_filegrp ()
	   Returns the default file group.

   Protected Member Functions
       void obtain_local_lock (size_t start, size_t fence)
       void release_local_lock (size_t start, size_t fence)

   Protected Attributes
       int me_
       int n_
       distsize_t * offsets_
       int debug_

Detailed Description
       The FileGrp abstract class provides a way of accessing distributed file
       in a parallel machine.

       Several specializations are available. For one processor, ProcFileGrp
       provides	a simple stub implementation. Otherwise, the specializations
       that should work	are MPIIOIFileGrp and MTMPIFileGrp.

       If a FileGrp is not given to the	program, then one will be
       automatically chosen depending on which MessageGrp is used by default,
       the type	of machine on which the	code was compiled, and what options
       were given at configuration time.

Member Function	Documentation
   virtual void	sc::FileGrp::catchup ()	[virtual]
       Processes outstanding requests. Some file group implementations don't
       have access to real shared memory or even active	messages. Instead,
       requests	are processed whenever certain file group routines are called.
       This can	cause large latencies and buffer overflows. If this is a
       problem,	then the catchup member	can be called to process all
       outstanding requests.

       Referenced by totalsize().

   static FileGrp* sc::FileGrp::initial_filegrp	(int & argc, char ** argv)
       [static]
       Create a	file group. This routine looks for a -filegrp argument,	then
       the environmental variable FILEGRP, and,	finally, the default
       MessageGrp object to decide which specialization	of FileGrp would be
       appropriate. The	argument to -integralgrp should	be either string for a
       ParsedKeyVal constructor	or a classname.	The default ThreadGrp and
       MessageGrp objects should be initialized	before this is called.

       Referenced by totalsize().

   virtual void* sc::FileGrp::obtain_readwrite (distsize_t offset, int size)
       [pure virtual]
       Only one	thread can have	an unreleased obtain_readwrite at a time. The
       actual file region locked can be	larger than that requested. If the
       file region is already locked this will block. For this reason, data
       should be held as read/write for	as short a time	as possible.

       Implemented in sc::ProcFileGrp.

       Referenced by totalsize().

   virtual void	sc::FileGrp::release_readwrite (void * data, distsize_t
       offset, int size) [pure virtual]
       This is called when read/write access is	no longer needed. The data
       will be unlocked.

       Implemented in sc::ProcFileGrp.

       Referenced by totalsize().

   static void sc::FileGrp::set_default_filegrp	(const Ref< FileGrp > &)
       [static]
       The default file	group contains the primary file	group to be used by an
       application.

       Referenced by totalsize().

   virtual void	sc::FileGrp::set_localsize (size_t) [pure virtual]
       Set the size of locally held data. When data is accessed	using a	global
       offset counting starts at node 0	and proceeds up	to node	n() - 1.

       Implemented in sc::ProcFileGrp.

       Referenced by n().

   virtual void	sc::FileGrp::sync () [pure virtual]
       Synchronizes all	the nodes. Consider using this when the	way you	you
       access data changes.

       Implemented in sc::ProcFileGrp.

       Referenced by totalsize().

Author
       Generated automatically by Doxygen for MPQC from	the source code.

Version	2.3.1			Mon Jul	3 2017			sc::FileGrp(3)

NAME | SYNOPSIS | Detailed Description | Member Function Documentation | Author

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