Ns2 project in adelaide

       Ns2 project in Adelaidein the initial definition of PARULEL, we allow conditional expressions in the LHS of ns2 project in Adelaide metarules. These conditions evaluate arithmetic expressions containing values bound in the ns2 project in adelaide object level rule instances. In certain cases one may want a more expressive ns2 project in adelaide metarule that computes some arbitrary “aggregate” condition on its LHS that is ns2 project in Adelaide applied to a set of matching base rule instances. For example, one may choose to fire a set of rule instances  if the number of those instances is greater than the number ns2 project in adelaide of instances generated by another distinct object level rule. We distinguish these two cases as “base” metarules and “aggregate” metarules. Each poses different problems ns2 project in Adelaide for metarule matching.

      The initial PARADISER implementation uses a replicated database configuration where multiple processing sites are involved in rule evaluation. Each processing site has a distinct constrained version of the rule program. Metarule matching is complicated by the fact that instances at one site may need to be nmcommunicated to ns2 project in Adelaide another site in order for a metarule to be matched fully.

    If we choose not to communicate instances and do all metalevel processing at each individual site, additional burden is ns2 project in Adelaide placed on the compile time distribution and reorganization subsystem, which is also responsible for load balancing of base rule evaluations the case of aggregate metarules, the point is moot; all instances might have to be comrnunicated to one site that computes ns2 project in Adelaide the aggregate function against the set of instances. Of course, it may be possible to compute the aggregate function in parallel among the sites if the function ns2 project in adelaide in question is associative mand commutative.

Ns2 project in Finland

      Ns2 project in Finland besides the issue of parallelism, RPL provides a declarative framework for conflict resolution like that proposed for PARULEL. However, it appears that the attributes of the firing groups used for conflict ns2 project in Finland resolution are hard-coded; there is no actual way of accessing the conflict set itself. Another system related to PARlJLEL is RDL. Although the execution semantics is defined as nondeterministic. choice for rule execution, control can be specified separately from the ns2 project in Finland rules by way of a control language based upon regular expressions.

       In early work , one of the authors defined a rule language controlled by a separate control language based upon regular expressions, that specified sequential, repetitive , alternative, and permutable  ns2 project in Finland rule executions. Although useful, the approach had a major problem in practice. Occasionally the control expression being followed required the execution of a ns2 project in Finland rule that had no instantiations. Ultimately, metarules were defined to resolve these “control conflicts”, which then quickly subsumed the entire regular expression language, metarules provided sufficient specification of c,ontrol.

     As we have noted, there is of ns2 project in Finland course the problem with strict specification of control sequences by way of rule names. It is impossible to specify control on the basis of data matched by rules, nor can ns2 project in Finland one specify control between instances of the same rule. PARULE’L’s metarules ameliorate these problems. PARULEL programs consist of a set of object-level rules which are matched against base relations  and a set of metarules that specify control ns2 project in Finland of rule execution by way of inhibiting the firing of rule instances. There are several issues related to the overall rule system that is relevant to efficient ns2 project in Finland matching of metarules, which we describe below.

Ns2 project in Yukon Territory

      Ns2 project in Yukon Territory the metarules of PARlJLEL enable the specification of either kind of control. However, they are best suited for expressing heuristic preferexes for the purpose of filtering a conflict set of rule instances ns2 project in Yukon Territory and obtaining a subset for concurrent firing. PARULEL has similarities with some existing rule languages, although the flexibility of the system in terms of the ability to customize the ns2 project in Yukon Territory conflict resolution method and the operational semantics in a “programmable” fashion for a particular application is unique. Consider RPL , a rule language with programmable conflict resolution expressed by metarules. Although there are obvious syntactic differences between RPL and PARULEL , there are also fundamental differences between the two.

       RPL appears to provide only tjwo mechanisms to express parallelism. The “all” ns2 project in Yukon Territory construct dictates that all instances of a rule should be fired. But this is useful only if all instances of a single rule can be fired at once without conflict, ns2 project in Yukon Territory otherwise one has t,o resort to “fire-one-instance” semantics.

   In contrast, PARIJLEL’s metarules provide the means of redacting unwanted instances of the same rule as well as different rules, and firing all that remain in parallel. The “firing group” construct of RPL is its second major construct that, is reminiscent of various rule ns2 project in Yukon Territory partitioning schemes in other earlier work . Here the idea of representing “commutative” rules by way of mutually exclusive rule clusters is provided. But nofurther optimizations are applied, and hence no large gain in parallelism can be expected PARULEL’s execution is intended to be optimized by way of copy-and-constraining  of rules ns2 project in Yukon Territory distributed to different processing sites. Optimizations may also be applied according to rule interdependence analysis as described in.

Ns2 project in Nova Scotia

       Ns2 project in Nova Scotia this section is a brief description of PARULE, a rule language with parallel execution semantics. ns2 project in Nova Scotia PARULEL syntax is derived from OPS5, while mits operational sernantic.s resemble those of Datalog’. PARULEL programs consist of “object-level” prodnction rules, “metarules” for a ns2 project in Nova Scotia programmable operational semantics, and a database of facts. Object-level rules consist of a conjunctive left–handside of conditions which are tested against the database of facts and a right hand side  of actions to be performed on the database. The LHS ns2 project in Nova Scotia corresponds to rule bodies of Datalog-style languages, and the RHS corresponds to rule heads. The object-level rules encode the basic, problem solving knowledge.

       The “programmable” conflict resolution strategy is realized via meta-level rules, ns2 project in Nova Scotia that express domaindependent relationships among the rule instantiations in ns2 project in Nova Scotia the conflict set at any given cycle. These metarules specify what specific types of interactions among rule instances indicate a conflict. The action of these metarules is to remove, or redact, one or more of the conflicting rule instances from the conflict set.

      The post-redaction conflict set is considered to be conflict-free, and can be fired concurrently, The ns2 project in Nova Scotia ease and flexibility with which control can be specified for problem solving has long been a useful metric for the richness of a programming language, and has ns2 project in Nova Scotia influenced language design considerably. In the PARULELlanguage, metarules express control. Control may involve the scheduling of sequential tasks, or expressing ns2 project in Nova Scotia preferences among competing parallel paths.

Ns2 project in Northwest Territories

      Ns2 project in Northwest Territories the result of this action is a balance of request generation and processing. Once this balance is achieved, continued monitoring by tracing queue size using the extended sensor discussed above ns2 project in Northwest Territories would be inefficient. Asa result, the ACturns this sensor off when it has not been notified of a “threshold exceeded” event for more than 1 min. However, since ns2 project in Northwest Territories external conditions, such as changes in Pyramid or Sun loads due to the activities of other users, may change over time, the ACperiodically polls the monitor for the ns2 project in Northwest Territories queue’s size.

       This polling is achieved by means of a probe. The additional costs of monitoring in this example derive from two messages due to the AC’sdynamic ns2 project in Northwest Territories change of the queue threshold to be used for its notification: one local message from AC to central monitor and one message from central to resident monitor, and three messages due to its dynamic deactivation of the sensor  one from the ACto central ns2 project in Northwest Territories monitor, one from central to resident monitor, and one from the resident monitor to the user program.

      The cost of probing after the desired balance has been achieved is small. Each probe consists of one local message from ACto central monitor, one probe request ns2 project in Northwest Territories across the network from central to resident monitor, one message from user process to resident monitor reporting the probe value, one return message from ns2 project in Northwest Territories resident monitor to central monitor, and one local return message from central monitor to AC. To summarize, this example suggests that probes are an ns2 project in Northwest Territories important element of any dynamic monitoring system that must be able to operate with variable overheads at different times during a program’s execution.

Ns2 project in Belgium

       Ns2 project in Belgium the analysis of monitoring information must be distributed and parallelized across the central and resident ns2 project in Belgium monitors and the user processes being monitored. The analysis of monitoring information by resident monitors is essential in order to reduce the message traffic within the monitoring system and to reduce the workload imposed on the central monitor. Some ns2 project in Belgium analysis may also be shifted to the extended sensor itself. For example, a significant improvement in monitoring performance for this example is gained when the ns2 project in Belgium event “threshold exceeded” is computed within the extended sensor itself, so that only a single event record must be transferred from the user program to the resident monitor.  

       To demonstrate the ns2 project in Belgium system’s dynamic variability regarding collection and analysis, and to indicate some tradeoffs between tracing and sampling, we continue monitoring after the ns2 project in Belgium addition of a second ship manager, and observe the performance effects of this adaptation. When doing this, the size of the request queue remains stable for some time after the second ship manager is added.

     However, due to the lack of actual parallelism in the execution ns2 project in Belgium of multiple ship managers on the Pyramid, a balance of request generation and processing is not achieved. To be notified of this imbalance, the ACdynamically ns2 project in Belgium changes the analysis performed by the resident monitor. In this case, it sets a new value for the queue threshold used by the resident monitor immediately after addition of the ns2 project in Belgium second ship manager. Upon being notified of the event “threshold of  exceeded,” the ACthen slows down request generation by the user process by increasing the amount of time it waits between issuing two consecutive commands from its script.

Ns2 project in Czech Republic

       Ns2 project in Czech Republic the monitor’s collection and analysis mechanisms are exercised as follows. For data collection, a traced, ns2 project in Czech Republic extended sensor is embedded into the queue manager’s code. This sensor computes the queue’s current size from the number of executions of queue element additions and deletions, and it notifies the resident monitor of each change in queue size. The ns2 project in Czech Republic resident monitor checks the current size of the queue against its threshold ns2 project in Czech Republic specified by the adaptation controller, in this case  It notifies the central monitor only when the event “threshold exceeded” occurs, as.

        The sensor is tumed on and off by the central and resident monitors in response to commands received from the AC. The ns2 project in Czech Republic distribution of analysis and collection is straightforward. The analysis required for notification of the central monitor and of the AC regarding the event “threshold exceeded” is ns2 project in Czech Republic performed within the user’s code and the resident monitor. As a result, the number of event records to be transferred from the resident to the central monitor is reducedby a factor of roughly fifty, thereby significantly reducing ns2 project in Czech Republic the network message traffic generated by monitoring.

      Specifically, two local messages and one network message are required to tum on the extended senso ns2 project in Czech Republic from AC to central monitor, from central monitor to resident monitor, and from resident monitor to user process. During game execution, the extended sensor generates ns2 project in Czech Republic approximately fifty event records, each recording the addition or deletion of a queue element; these records are sent to the resident monitor as local messages. One message is sent by the resident monitor to notify the central monitor of the event “threshold exceeded.”

Ns2 project in Croatia

      Ns2 project in Croatia the description of the two-dimensional sea is partitioned into sections, with a section manager process responsible for each section. Ship manager processes are responsible for handling requests ns2 project in Croatia dealing with ships, such as moving and firing. All requests are placed into a single, logically centralized queue, maintained by a queue manager process. Ship managers take and ns2 project in Croatia process requests from this queue. The game is driven from a script, with multiple user processes reading this script and issuing requests to the queue manager.

       This distributed ns2 project in Croatia application illustrates several aspects of the monitoring system, including: the operation of the monitor’s distributed components; the interaction between the monitoring ns2 project in Croatia system and other Issos tools; the tradeoffs regarding the use of the monitor’s various collection mechanisms and the tradeoffs regarding the distribution of information analysis; and ns2 project in Croatia the tradeoffs between tracing and sampling of program execution.Dynamicmonitoring–basicrequirements.

         The usefulness of dynamic monitoring is demonstrated using a small ns2 project in Croatia version of the game, consisting of a user and a ship manager process executing on the Pyramid, and a queue manager process executing on a Sun workstation The ns2 project in Croatia monitoring system’s components are the central monitor, the PCS, and the AC executing on the Pyramid and the resident monitor executing on the Sun. This  demonstrates ns2 project in Croatia the dynamic, joint operation of the central and resident monitors with the AC and PCS. The purpose of this cooperation is to balance the rates of request generation by the user process and request processing by the ship manager. The monitoring statement ns2 project in Croatia instructs the monitor to notify the AC when the size of the request queue maintained by the queue manager process.

Ns2 project in Bulgaria

     Ns2 project in Bulgaria these measurements imply that a single resident monitor may fully utilize its processor if all other processors ns2 project in Bulgaria on the ten-node Encore Multimax generate events at the fastest possible rate. Similar results should hold for the -based Encore machines now in use.

     However, as with the ns2 project in Bulgaria real-time multiprocessor, excessive communication with the central monitor will result ilowutilization of the dedicated Encore node. We have observed similar results on a BBN Butterfly multiprocessor with another version of the monitoring system .

      To summarize, ns2 project in Bulgaria it appears that both the configuration of the monitoring system in terms of resident and central monitors and the selection of appropriate monitoring plans using probes ns2 project in Bulgaria and sensors, depend on the characteristics of the underlying hardware and on application characteristics or requirements stated with the attribute and view languages. It would be ns2 project in Bulgaria interesting to consider the automatic derivation of such application requirements from information supplied by the programming environment or by the ns2 project in Bulgaria adaptation controller This section describes a program monitoring and adaptation that highlights some of the design and implementation issues in distributed, dynamic monitoring.

      This example uses the Issos parallel programming environment This game shares ns2 project in Bulgaria one aspect with many parallel and distributed programs, including parallel branchand- bound applications , parallel MultiLisp programs , and others. Namely, the game is ns2 project in Bulgaria subject to problems with workload balancing, since the program dynamically generates and consumes units of work that cannot be predicted statically The game consists of ships moving on a sea.

Ns2 project in Vienna

      Ns2 project in Vienna this multiprocessor was composed of seven nodes, each containing an Intel  processor, which is somewhat slower than the Motorola  processors in our Sun- workstations. First, in this system, the relative ns2 project in vienna cost of sending messages within and among different processors is lower than in Unix. Specifically, the GEM real-time operating system executing on this multiprocessor provides ns2 project in Vienna  message sending primitives that can transmit small messages  within 1 ms, compared wit between somewhat faster Sun workstations. Second, this message ns2 project in Vienna communication overhead is roughly equivalent to the overhead of process switching in GEM .

      Third, the bandwidthof the bus connecting different ns2 project in Vienna multiprocessor nodes is quite high and generally underutilized  . Fourth, the multiprocessor’s link to the monitoring system’s user interface   has comparatively low bandwidth and ns2 project in Vienna high latency compared to the intra-multiprocessor links. Asa result, for this hardware configuration, we dedicated a single processor to the execution of a single resident monitor. Sensors and ns2 project in Vienna extended sensors send event records to this resident monitor at a cost of roughly ns2 project in Vienna per event record.

    The resident monitor performs all analyses not done by extended sensors and it also performs those analyses done by the central monitor in the distributed system  A similar monitoring architecture was adopted for an Encore Multimax multiprocessor, which could be used for execution of selected components of a parallel/distributed program ns2 project in Vienna mapped to a set of Sun workstations and the Encore Multimax . Here, a single Unix process acting as a resident monitor is responsible for all application processes executing on the Encore machine. ns2 project in Vienna this resident monitor sends event records to the central monitor executing on a Sun workstation, which may also communicate with resident monitors located on other Sun workstations.