Description
Competers (CPXs) are one of CDLs less frequently used objects. Most of the time multiple consumers share events that emanate from a single provider but occasionally the opposite is required and the application logic specifically requires that the consumers compete (farming out tasks to balance load etc). Each connected consumer competes for each event provided to the competer on a first come first serve basis. Distributors can be thought of as the opposite of competers in that they ensure that all consumed events are shared by all connectors. In most cases competers are actually gratuitous because 'competing' is the default behavior for most objects that are not explicitly distributed. They are therefore typically used with distributors, demultiplexors, splitters, logical semaphores and arbitrated stores.
Creation Attributes
Name
Instance name (see Object Names)
Dimensions
Instance dimensionality (see Object Dimensionality)
Presence
Instance presence flag (see Object Presence)
Reentrancy
Instance reentrancy (see Object Reentrancy)
Visibility
Instance visibility flag (see Object Visibility)
Connection Attributes
Event propagator objects have two types of connection. Those that provide events to their consuming faces, and those that consume events from their providing faces. The attributes associated with any particular connection therefore depend on the providing and consuming object types (see Automatic Connections).
All automatic connections require;
Timeout
This attribute determines whether the connection will poll or block (see Connection Timeout).
Signature
This attribute is a string that describes the mapping from elements in the consumer, to elements in the provider. See Connection Mappings.
Dimensions
This attribute determines the dimensionality of the connection array owned by each consuming element. By default, this will provide the consuming element with one connection for each provider element. Collector, Multiplexor and Manual connection consumers can have multi-dimensional connection arrays, but in all other cases, this attribute will be '1'. See Connection Mappings.
Repeat Count
This attribute determines the number of times that each 'provider element to consumer element' connection is repeated. If the repeat count is greater then one, then the Dimension attribute (above), and the resulting connection access functions, will both have an 'extra' dimension. Only Collector, Multiplexor and Manual connection consumers can have repeat counts that are greater than '1'. See Connection Mappings.
Name
This attribute determines the connection's 'name' which is used to construct access function names (see Connection Names).
There are no specific attributes required for connections that provide events to a competer's consuming face.
There are no specific attributes required for connections that consume events from a competer's providing face.
Manual Connections
Manual connections provide a means of directly accessing target objects. These are created automatically from CDL diagrams and accessed using their access function names (see Manual Connections).
Competer connections provide the following member functions;
WaitEvent()
This member function issues an 'open' request to the competer (see CPX WaitEvent function).
Close()
This member function closes a previously opened competer (see CPX Close function).
Automatic and Manual Connections
The following member functions can be used to retrieve information from both automatic and manual connections;
IsOpen()
This member function returns TRUE if the connection is 'Open' or FALSE otherwise.
EventNum()
This member function returns the retrieved event's sequence number. Numbering starts from zero (the first retrieved event).
Example
See Competing for a Distributed Event.