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<H1> E.1 Partitions</H1>
<DIV Class="Paranum"><FONT SIZE=-2>1</FONT></DIV>
<DIV Class="Normal"> [The partitions of a distributed program are classified
as either active or passive.] </DIV>
<H4 ALIGN=CENTER>Post-Compilation Rules</H4>
<DIV Class="Paranum"><FONT SIZE=-2>2</FONT></DIV>
<DIV Class="Normal"> <A NAME="I6948"></A><A NAME="I6949"></A>An <I>active
partition</I> is a partition as defined in <A HREF="AA-10-2.html">10.2</A>.
A <I>passive partition</I> is a partition that has no thread of control
of its own, whose library units are all preelaborated, and whose data
and subprograms are accessible to one or more active partitions. </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>2.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Discussion: </B>In most situations,
a passive partition does not execute, and does not have a ``real'' environment
task. Any execution involved in its elaboration and initialization occurs
before it comes into existence in a distributed program (like most preelaborated
entities). Likewise, there is no concrete meaning to passive partition
termination. </FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>3</FONT></DIV>
<DIV Class="Normal"> A passive partition shall include only <FONT FACE="Arial, Helvetica">library_item</FONT>s
that either are declared pure or are shared passive (see <A HREF="AA-10-2-1.html">10.2.1</A>
and <A HREF="AA-E-2-1.html">E.2.1</A>).</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>4</FONT></DIV>
<DIV Class="Normal"> An active partition shall be configured on a processing
node. A passive partition shall be configured either on a storage node
or on a processing node.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>5</FONT></DIV>
<DIV Class="Normal"> The configuration of the partitions of a program
onto a distributed system shall be consistent with the possibility for
data references or calls between the partitions implied by their semantic
dependences. <A NAME="I6950"></A>Any reference to data or call of a subprogram
across partitions is called a <I>remote access</I>. </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>5.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Discussion: </B>For example,
an active partition that includes a unit with a semantic dependence on
the declaration of another RCI package of some other active partition
has to be connected to that other partition by some sort of a message
passing mechanism.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>5.b</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1>A passive partition that is accessible
to an active partition should have its storage addressable to the processor(s)
of the active partition. The processor(s) should be able to read and
write from/to that storage, as well as to perform ``read-modify-write''
operations (in order to support entry-less protected objects).</FONT></DIV>
<H4 ALIGN=CENTER>Dynamic Semantics</H4>
<DIV Class="Paranum"><FONT SIZE=-2>6</FONT></DIV>
<DIV Class="Normal"> <A NAME="I6951"></A>A <FONT FACE="Arial, Helvetica">library_item</FONT>
is elaborated as part of the elaboration of each partition that includes
it. If a normal library unit (see <A HREF="AA-E-2.html">E.2</A>) has
state, then a separate copy of the state exists in each active partition
that elaborates it. [The state evolves independently in each such partition.]</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>6.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Ramification: </B>Normal library
units cannot be included in passive partitions. </FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>7</FONT></DIV>
<DIV Class="Normal"> <A NAME="I6952"></A><A NAME="I6953"></A><A NAME="I6954"></A><A NAME="I6955"></A>[An
active partition <I>terminates</I> when its environment task terminates.]
A partition becomes <I>inaccessible</I> if it terminates or if it is
<I>aborted</I>. An active partition is aborted when its environment task
is aborted. In addition, if a partition fails during its elaboration,
it becomes inaccessible to other partitions. Other implementation-defined
events can also result in a partition becoming inaccessible. </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>7.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Implementation defined: </B>Any
events that can result in a partition becoming inaccessible.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>8/1</FONT></DIV>
<DIV Class="Normal" Style="margin-bottom: 0.4em"> For a <U><FONT FACE="Arial, Helvetica">prefix</FONT></U><S>prefix</S>
D that denotes a library-level declaration, excepting a declaration of
or within a declared-pure library unit, the following attribute is defined:
</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>9</FONT></DIV>
<DL Class="Hanging"><DT> D'Partition_ID<DD Class="Hanging">
<A NAME="I6956"></A><A NAME="I6957"></A>Denotes a value of the type <I>universal_integer</I>
that identifies the partition in which D was elaborated. If D denotes
the declaration of a remote call interface library unit (see <A HREF="AA-E-2-3.html">E.2.3</A>)
the given partition is the one where the body of D was elaborated. </DL>
<H4 ALIGN=CENTER>Bounded (Run-Time) Errors</H4>
<DIV Class="Paranum"><FONT SIZE=-2>10</FONT></DIV>
<DIV Class="Normal"> <A NAME="I6958"></A>It is a bounded error for
there to be cyclic elaboration dependences between the active partitions
of a single distributed program. <A NAME="I6959"></A>The possible effects
are deadlock during elaboration, or the raising of Program_Error in one
or all of the active partitions involved. </DIV>
<H4 ALIGN=CENTER>Implementation Permissions</H4>
<DIV Class="Paranum"><FONT SIZE=-2>11</FONT></DIV>
<DIV Class="Normal"> An implementation may allow multiple active or
passive partitions to be configured on a single processing node, and
multiple passive partitions to be configured on a single storage node.
In these cases, the scheduling policies, treatment of priorities, and
management of shared resources between these partitions are implementation
defined. </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>11.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Implementation defined: </B>The
scheduling policies, treatment of priorities, and management of shared
resources between partitions in certain cases.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>12</FONT></DIV>
<DIV Class="Normal"> An implementation may allow separate copies of
an active partition to be configured on different processing nodes, and
to provide appropriate interactions between the copies to present a consistent
state of the partition to other active partitions. </DIV>
<DIV Class="Paranum"><FONT SIZE=-2>12.a</FONT></DIV>
<DIV Class="Annotations"><FONT SIZE=-1><B>Ramification: </B>The language
does not specify the nature of these interactions, nor the actual level
of consistency preserved. </FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>13</FONT></DIV>
<DIV Class="Normal"> In an implementation, the partitions of a distributed
program need not be loaded and elaborated all at the same time; they
may be loaded and elaborated one at a time over an extended period of
time. An implementation may provide facilities to abort and reload a
partition during the execution of a distributed program.</DIV>
<DIV Class="Paranum"><FONT SIZE=-2>14</FONT></DIV>
<DIV Class="Normal"> An implementation may allow the state of some
of the partitions of a distributed program to persist while other partitions
of the program terminate and are later reinvoked. </DIV>
<DIV Class="NotesHeader"><FONT SIZE=-1>NOTES</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>15</FONT></DIV>
<DIV Class="Notes"><FONT SIZE=-1>3 Library units are grouped
into partitions after compile time, but before run time. At compile time,
only the relevant library unit properties are identified using categorization
pragmas.</FONT></DIV>
<DIV Class="Paranum"><FONT SIZE=-2>16</FONT></DIV>
<DIV Class="Notes"><FONT SIZE=-1>4 The value returned by the
Partition_ID attribute can be used as a parameter to implementation-provided
subprograms in order to query information about the partition.</FONT></DIV>
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