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sc::MemoryGrp(3)		     MPQC		      sc::MemoryGrp(3)

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

SYNOPSIS
       #include	<memory.h>

       Inherits	sc::DescribedClass.

       Inherited by sc::MsgMemoryGrp, and sc::ProcMemoryGrp.

   Public Member Functions
       MemoryGrp (const	Ref< KeyVal > &)
       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	memory.
       size_t localsize	()
	   Returns the amount of memory	residing locally on me().
       virtual void * localdata	()=0
	   Returns a pointer to	the local data.
       distsize_t localoffset ()
	   Returns the global offset to	this node's memory.
       int size	(int node)
	   Returns the amount of memory	residing on node.
       distsize_t offset (int node)
	   Returns the global offset to	node's memory.
       distsize_t totalsize ()
	   Returns the sum of all memory allocated on all nodes.
       virtual void activate ()
	   Activate is called before the memory	is to be used.
       virtual void deactivate ()
	   Deactivate is called	after the memory has been used.
       virtual void * obtain_writeonly (distsize_t offset, int size)=0
	   This	gives write access to the memory 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 memory	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 * malloc_local (size_t nbyte)
	   Allocate data that will be accessed locally only.
       virtual double *	malloc_local_double (size_t ndouble)
       virtual void free_local (void *data)
	   Free	data that was allocated	with malloc_local_double.
       virtual void free_local_double (double *data)
       virtual void catchup ()
	   Processes outstanding requests.
       virtual void print (std::ostream	&o=ExEnv::out0()) const
	   Prints out information about	the object.

   Static Public Member	Functions
       static MemoryGrp	* initial_memorygrp (int &argc,	char **argv)
	   Create a memory group.
       static MemoryGrp	* initial_memorygrp ()
       static void set_default_memorygrp (const	Ref< MemoryGrp > &)
	   The default memory group contains the primary memory	group to be
	   used	by an application.
       static MemoryGrp	* get_default_memorygrp	()
	   Returns the default memory 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 MemoryGrp abstract class provides a way of accessing	distributed
       memory in a parallel machine.

       Several specializations are available. For one processor, ProcMemoryGrp
       provides	a simple stub implementation. Parallel specializations include
       ShmMemoryGrp, MTMPIMemoryGrp, and ARMCIMemoryGrp. The particular
       specializations that work depend	highly on the target hardware and
       software	environment.

Member Function	Documentation
   virtual void	sc::MemoryGrp::catchup () [virtual]
       Processes outstanding requests. Some memory group implementations don't
       have access to real shared memory or even active	messages. Instead,
       requests	are processed whenever certain memory 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.

   static MemoryGrp* sc::MemoryGrp::get_default_memorygrp () [static]
       Returns the default memory group. If the	default	memory group has not
       yet been	set, then one is created. The particular specialization	used
       is determined by	configuration options and which	specializations	are
       being used for MessageGrp and ThreadGrp.

   static MemoryGrp* sc::MemoryGrp::initial_memorygrp (int & argc, char	**
       argv) [static]
       Create a	memory group. This routine looks for a -memorygrp argument,
       and then	the environmental variable MEMORYGRP to	decide which
       specialization of MemoryGrp would be appropriate. The argument to
       -memorygrp or the value of the environmental variable should be either
       string for a ParsedKeyVal constructor or	a classname. The default
       ThreadGrp and MessageGrp	objects	should be initialized before this is
       called.

       References initial_memorygrp().

       Referenced by initial_memorygrp().

   virtual void* sc::MemoryGrp::malloc_local (size_t nbyte) [virtual]
       Allocate	data that will be accessed locally only. Using this for	data
       that will be used for global operation can improve efficiency. Data
       allocated in this way must be freed with	free_local_double.

       Reimplemented in	sc::ARMCIMemoryGrp.

   virtual void* sc::MemoryGrp::obtain_readwrite (distsize_t offset, int size)
       [pure virtual]
       Only one	thread can have	an unreleased obtain_readwrite at a time. The
       actual memory region locked can be larger than that requested. If the
       memory 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::ShmMemoryGrp,	sc::RDMAMemoryGrp, sc::ProcMemoryGrp,
       and sc::ActiveMsgMemoryGrp.

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

       Implemented in sc::ShmMemoryGrp,	sc::RDMAMemoryGrp, sc::ProcMemoryGrp,
       and sc::ActiveMsgMemoryGrp.

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

       Implemented in sc::ShmMemoryGrp,	sc::ProcMemoryGrp, sc::ARMCIMemoryGrp,
       sc::ActiveMsgMemoryGrp, sc::RDMAMemoryGrp, and sc::MsgMemoryGrp.

   virtual void	sc::MemoryGrp::sync () [pure virtual]
       Synchronizes all	the nodes. This	is useful after	remote memory writes
       to be certain that all of the writes have completed and the data	can be
       accessed	locally, for example.

       Implemented in sc::ProcMemoryGrp, sc::MTMPIMemoryGrp, sc::MsgMemoryGrp,
       and sc::ARMCIMemoryGrp.

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

Version	2.3.1			Thu Dec	2 2021		      sc::MemoryGrp(3)

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

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