gridsim-commits Mailing List for GridSim: A Grid Simulation Toolkit (Page 3)

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Revision: 228
          http://gridsim.svn.sourceforge.net/gridsim/?rev=228&view=rev
Author:   mkrystek
Date:     2008-08-20 13:13:52 +0000 (Wed, 20 Aug 2008)

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    branches/gssim/faq.txt

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--- branches/gssim/faq.txt	                        (rev 0)
+++ branches/gssim/faq.txt	2008-08-20 13:13:52 UTC (rev 228)
@@ -0,0 +1,458 @@
+# Frequently Asked Questions (FAQ)
+# Maintained by Anthony Sulistio
+# $Id: faq.txt,v 1.7 2007/09/01 02:46:01 anthony Exp $
+
+Please read this document, FAQ, examples, API, etc before contacting us.
+Moreover, look at the previous questions at the below website:
+http://sourceforge.net/mail/?group_id=94592
+
+Send any queries and feedbacks to gridsim-users @ lists.sourceforge.net
+
+---------------------------------------------------------
+Q: Where can I find gridbroker, visual modeler, ... ?
+
+A: If you are looking for applications or programs built on top of GridSim,
+such as gridbroker or Visual Modeler, they can be found below:
+http://www.gridbus.org/gridsim/release.html
+
+---------------------------------------------------------
+Q: I want to run the gridsim simulation on my computer but i can't because
+   Jcreator don't see the gridsim package. Please send to me the steps of
+   how compile and run the simulation.
+
+A: Go to GridSim website and there is an instruction on how to use it with
+   JCreator. http://www.gridbus.org/gridsim/paper/jcreator.pdf
+
+   If you use JBuilder or Eclipse, the instructions can be found below:
+   http://www.gridbus.org/gridsim/paper/jbuilder.pdf
+   http://www.gridbus.org/gridsim/paper/eclipse.pdf
+
+---------------------------------------------------------
+Q: I would like to do some experiments for my research work on grid computing
+   using the simulator package that you have. Using the simulator,
+   can I simulate a grid environment with service providers requestors,
+   administartors etc. on a PC environment? Please pass on some resources,
+   links, and white papers and links where from I should download.
+
+Q: please help me by sending GridSim Package, give instructions and
+   also technical help to complete my project successfully.
+
+A: The best way to learn GridSim is by downloading it from below:
+   http://www.gridbus.org/gridsim/
+
+   Go through the provided examples.
+   In the website, it contains links to papers about GridSim.
+
+   As long as you have JDK version 1.4 onwards, you can run GridSim
+   on a PC. However, if you run a huge simulation, you'd probably needs
+   bigger RAM and CPU.
+
+---------------------------------------------------------
+Q: Will GridSim require Globus?
+
+A: Why don't you download the GridSim toolkit and have a try?
+   Also, please read the README file.
+
+---------------------------------------------------------
+Q: How do you compile and run GridSim application?
+
+A: For example, if you want to run Example1
+
+   In Unix/Linux:
+   * go to the directory of where Example1 resides, i.e.
+     at command prompt type: cd $GRIDSIM/examples/Example01
+   * to compile type:  javac -classpath $GRIDSIM/gridsim.jar:. Example1.java
+   * to run type: java -classpath gridsim.jar:. Example1
+
+   In Windows:
+   * go to the directory of where Example1 resides, i.e.
+     at command prompt type: cd %GRIDSIM%\examples\Example01
+   * to compile type:  javac -classpath %GRIDSIM%\gridsim.jar;. Example1.java
+   * to run type: java -classpath gridsim.jar;. Example1
+
+
+   The main difference is the use of ":" for Unix/Linux, and ";" for Windows
+   NOTE: $GRIDSIM or %GRIDSIM% is the location of the GridSim Toolkit package.
+         Also, inside gridsim.jar contains SimJava v2.0 classes. Hence,
+         you do not need to install SimJava libraries.
+
+---------------------------------------------------------
+Q: When I run GridSim application, I have the following error message:
+        Exception in thread "main" java.lang.NoClassDefFoundError: Example1
+
+A: You need the classpath to refer to the directory where Example1.java
+   located. For Example, to run in Windows:
+        java -classpath gridsim.jar;. Example1
+
+   where Example1 is the classname you want to execute
+
+---------------------------------------------------------
+Q: My GridSim application runs perfectly, however, after the end of simulation
+   it just hang without exiting properly.
+
+A: The problem may be caused by not closing GridSim entities, such as
+   GridStatistics, I/O ports, etc. Each class that extends GridSim with
+   a networked I/O ports must use terminate the I/O entities by using
+   terminateIOEntities() before exiting body() method.
+
+   Another cause for this problem is the number of Grid user entities.
+   Before the start of a GridSim application, you need to intialize the GridSim
+   package using GridSim.init(). The method requires to have the number of
+   Grid user entities. If the number is different from the actual Grid user
+   entities, your GridSim application will hang or can't exit properly.
+
+---------------------------------------------------------
+Q: I am creating a network topology using GridSim. When I run the experiment,
+I have the following exception message:
+
+java.lang.NullPointerException
+   at gridsim.net.RIPRouter.getScheduler(RIPRouter.java:451)
+   at gridsim.net.RIPRouter.getScheduler(RIPRouter.java:401)
+   at gridsim.net.RIPRouter.processNetPacket(RIPRouter.java:302)
+   at gridsim.net.RIPRouter.processEvent(RIPRouter.java:270)
+   at gridsim.net.Router.body(Router.java:267)
+   at eduni.simjava.Sim_entity.run(Sim_entity.java:603)
+
+A: Network exception message is generally caused by 2 things:
+- If you created a new router or link entity, it hasn't been registered to
+GridInformationService class; OR
+
+- GridSim needs few seconds for all network entities to be registered and
+for the network entity to fill in its routing table dynamically.
+Currently, GridSim uses a flooding approach for locating the neighbour
+routers. Hence, these routers need time to receive all the replies.
+I think this could be the main cause of the exception message.
+
+---------------------------------------------------------
+Q: When running GridSim Example 4, 5 and 6 I got an infinite loop
+   saying: "Waiting to get list of resources".
+
+A: In GridSim 2.1, GridSim.getGridResourceList() uses a message event
+   to tell GIS (GridInformationService) entity to send the GridResource
+   list. This causes a significant delay and a bit redundant.
+
+   In GridSim 2.2, GridSim.getGridResourceList() directly uses a
+   method call to GIS entity rather than a message passing.
+   This makes the operation a lot faster. However, during the early stage
+   of simulation, a GridResource might be slow in registering its service
+   to GIS. Hence, the GridResource list is always empty and causing
+   an infinite loop.
+
+   To solve this problem, inside the while() loop, put the following
+   code:
+            // need to pause for a while to wait GridResources finish
+            // registering to GIS
+            super.gridSimHold(1.0);    // hold by 1 second
+
+   So, you wait 1 second later to get GridResource list.
+
+---------------------------------------------------------
+Q: When I tried to run GridSim Example4, I have the following error message:
+    java.lang.IncompatibleClassChangeError
+        at Example4.body(Example4.java:70)
+        at eduni.simjava.Sim_entity.run(Sim_entity.java:603)
+
+A: I am not sure what is the exact problem. However, this is mainly
+   caused by older release of SimJava. GridSim Toolkit 2.2 and above now use
+   SimJava2. Simply recompile the Example4.java will solve this
+   problem.
+
+   NOTE: This problem is also effected GridSim Example6.
+
+---------------------------------------------------------
+Q: When I tried to run GridSim Example1, I have the following error message:
+    Exception in thread "main" eduni.simjava.Sim_exception:
+    Sim_entity: Entity names can't contain spaces.
+        at eduni.simjava.Sim_entity.<init>(Sim_entity.java:154)
+        at gridsim.GridSim.<init>(GridSim.java:149)
+        at gridsim.GridResource.<init>(GridResource.java:93)
+        at Example1.createGridResource(Example1.java:188)
+        at Example1.main(Example1.java:57)
+
+A: GridSim Toolkit 2.2 and above now use SimJava2. SimJava2 is more strict about
+   a valid entity name compare to previous release. Hence, to fix this
+   problem is to remove the unnecessary empty space, i.e.
+   "GridResource 0" becomes "GridResource_0"
+
+---------------------------------------------------------
+Q: Are there any type of applications that I can simulate with GridSim?
+
+A: GridSim provides the grid simulation environment (with resources and
+   users), but you need to write codes specifically for the application you
+   want to simulate, e.g. a resource broker Nimrod/G is written to call
+   GridSim classes.
+
+---------------------------------------------------------
+Q: How do I create Gridlets with compute I/O requirements?
+
+A: Gridlets with compute I/O requirements are simulated through their file
+   sizes (input) and output sizez (output) parameters.
+   See Figure 16 of the GridSim paper.
+
+---------------------------------------------------------
+Q: I have a question on network simulation in Gridsim.
+   In my understanding, entities with networking capability must define
+   input and output port. Both ports are "connected" to a simulated network.
+   How does Gridsim models network link and its characteristics, especially
+   bandwidth, since I couldn't find class that models this network link?
+   Does Gridsim also simulate bandwidth-sharing if there are several IOdata
+   are sent using the same link?
+
+A: Not supported in the older versions. Currently GridSim uses very
+   simple network model.
+
+   Since GridSim ver3.1, it has a realistic network model. However,
+   advanced network features are not supported.
+
+---------------------------------------------------------
+Q: Is GridSim tool kit provides any help in solving problems for dynamical
+   resource allocation upon failure?
+
+A: GridSim provides mechanism to reserve, but policy of reservation and
+   how to handle failures etc. is up to server's provider and consumers
+   to define.
+
+---------------------------------------------------------
+Q: How do you model the gridlet execution in time_shared resource?
+
+A: Just creating a Gridlet is sufficient. It runs on both time and space
+   shared machines.
+
+---------------------------------------------------------
+Q: Does each gridlet can only be processed by only one PE?
+
+A: For older GridSim versions, it runs one PE.
+   Since GridSim ver3.0, each Gridlet can ask to be run on multiple PEs.
+   However, it is up to the scheduler to handle this.
+   At the moment, by default, TimeShared and SpaceShared scheduler executes
+   an incoming Gridlet to only 1 PE.
+
+---------------------------------------------------------
+Q: Is the model for parallel job included inside the GridSim?
+
+A: It is up users to model parallel application job at the higher level
+   (develop on top of gridsim).
+
+---------------------------------------------------------
+Q: When I run GridSim, I have the following error message:
+        Sim_system:Error - past event detected!
+        Time: 0.0, event time: -XXXXX.X event type: 1
+        Where XXXXX.X is a negative number that varies.
+
+A: It appears like this error comes up for one of the following scenarios:
+   - an entity or object waits for a specific event. However, the response
+     event type is different.
+   - some events are not captured.
+   - GridSim runs under multi-threaded environment. Hence, some events might
+     be accidentally deleted or being changed by other thread to wait for
+     a different response that doesn't exist, etc ...
+
+---------------------------------------------------------
+Q: Does GridSim currently support the usage of any wireless network standard
+when specifying network topology?
+
+A: No. We have NOT done so much about wireless network support in GridSim.
+   But if you are willing, we could explore this with you.
+
+---------------------------------------------------------
+Q: Does GridSim support multiple simulations or runs in a single program?
+
+A: No. Currently, GridSim only allows a single experiment to run in a main()
+   method. Hence, to calculate a confidence interval, you need to do this
+   manually.
+
+---------------------------------------------------------
+Q: Does GridSim run in a cluster or a PC?
+
+A: GridSim runs in a PC as a stand-alone program with multiple threads.
+   This means if you want to run in a cluster, you just need to request 1 node.
+
+---------------------------------------------------------
+Q: I came across three variables: peak load, off-peak load and holiday load.
+   I understand from the study I have done that these variables represent
+   the load factor. I do not fully get what this means and was hoping that
+   you could help me out so I can progress further with my work.
+
+A: These load factors are influencing the total execution time
+   of a job in a given resource.
+   If you set these loads to zero, means this resource is idle / free.
+   If you want to write a resource scheduler, like SpaceShared or TimeShared
+   then these load factors are important.
+
+---------------------------------------------------------
+Q: for the Gridlet class, what are the units of file size, length, and output?
+
+A: the unit of file size and output is in byte.
+   For the Gridlet length, the unit is in MI (Millions Instructions).
+   A CPU clock is measured in MIPS (Millions Instructions Per Second) as
+   suggested by SPEC.
+
+---------------------------------------------------------
+Q: In the previous releases of GridSim you had to use
+GridSim class to send messages to other entities. The provided "send" methods
+included a parameter to indicate the sender of the request. It is no clear how
+to indicate this with the "send" methods provided by the GridSimCore class. The
+lack of ID information in the event raises an exception in the GridResource
+class. Reading the source code of the GridResource class I've realized that the
+way to send the ID of the sender could be the following:
+
+super.send(resourceId, GridSimTags.SCHEDULE_NOW,
+GridSimTags.RESOURCE_CHARACTERISTICS, new Integer(this.get_id()));
+
+This solves the first problem but generates a new exception in other class:
+Exception in thread "Thread-7" java.lang.ArrayIndexOutOfBoundsException: -1
+       at java.util.ArrayList.get(ArrayList.java:323)
+       at eduni.simjava.Sim_system.send(Sim_system.java:600)
+       at eduni.simjava.Sim_entity.sim_schedule(Sim_entity.java:342)
+       at gridsim.net.Output.defaultSend(Unknown Source)
+       at gridsim.net.Output.body(Unknown Source)
+       at eduni.simjava.Sim_entity.run(Sim_entity.java:603)
+
+I've read the source of the Output class, but I've not found a solution to the
+problem. Do you know where can be the problem?
+
+A: The problem was in the "baudRate" attribute that wasn't initialized.
+So using GridSim(String name, double baudRate) the problem was solved.
+
+---------------------------------------------------------
+
+
+
+Questions related to GridBroker
+===============================
+
+Q: How do you compile and run GridBroker application?
+
+A: Similar to compile and to run GridSim. Instead of using gridsim.jar,
+   you use gridbroker.jar. Inside this jar file, it contains GridBroker,
+   GridSim and SimJava classes.
+
+   Please do not use recent GridSim release jar file when running this broker
+   (see the below question).
+
+---------------------------------------------------------
+Q: I have executed all gridsim examples. But while executing gridbroker
+i.e C:\gridsimtoolkit-4.0\application\gridbroker\example\Example1.java
+it gives following error after initializing gridsim:
+
+Initialising...
+Starting GridSim version 4.0
+Entities started.
+java.lang.IncompatibleClassChangeError
+ at gridbroker.Broker.body( Broker.java:649)
+ at eduni.simjava.Sim_entity.run(Sim_entity.java:603)
+
+
+A: read the README.txt file located under $GRIDSIM/application/gridbroker.
+./gridbroker.jar  - A jar file containing GridBroker, GridSim v2.1, and
+                    SimJava v1.2 classes.
+NOTE: No updates or improvements on GridBroker package since GridSim v2.1,
+hence, it is more stable under GridSim v2.1 and SimJava v1.2 release.
+
+You cant mixed up jars from different class versions.
+That's why you have this error message.
+
+---------------------------------------------------------
+Q: I want to create a specific application. Is it necessary to build on top
+   of GridBroker?
+
+A: You are expected to develop an application on top of GridSim,
+   instead of GridBroker. GridBroker is included to demonstrate the
+   capability of GridSim in simulating the Grid environment and a
+   Nimrod/G like deadline and budget constraint scheduling system.
+
+---------------------------------------------------------
+Q: The application generates the files: tracefile, stat.txt, g14.sched1,
+   g14.sched2, g14.sched3, g14.sched31, g14.sched4, g14.sched5, g14.sched6.
+   What are the meaning of these files?
+
+A: These files contains statistical results of the simulation that are of
+   interest to the GridSim user (ie. you).
+
+   When running a GridBroker application, it will produce the following files:
+
+        stat.txt -> created by GridSim class during GridSim.init() to create
+                    a GridStatistics object for statistical purposes
+
+        tracefile -> created by the SimJava package to trace every events
+                     that are performed by SimJava, GridSim and GridBroker
+                     during the simulation.
+
+        g14.sched* -> All of these files are created by Broker class.
+                      When we create an UserEntity object, it will
+                      automatically creates a Broker object.
+
+    Description on the g14.sched* files:
+        g14.sched1 is about Gridlets finished report.
+        g14.sched2 is about Gridlets processing expenses report.
+        g14.sched3 is about Gridlets on resource report.
+        g14.sched31 is about Gridlets committed for resource report.
+        g14.sched4 is same as g14.sched1, however this file only
+            displays the overall result or summary of g14.sched1 file.
+
+        g14.sched5 is same as g14.sched2, however this file only
+            displays the overall result or summary of g14.sched2 file.
+
+        g14.sched6 is same as g14.sched3, however this file only
+            displays the overall result or summary of g14.sched3 file.
+
+    NOTE: Explanations about the content of each file are mentioned in
+          GridBroker example section.
+
+---------------------------------------------------------
+
+
+Questions related to VisualModeler
+==================================
+
+
+Q: What is VisualModeler (VM)?
+
+A: It is a program that generates GridBroker source code.
+   With VM, you can specify how many grid users and resources for your
+   simulation. After finish generating the GridBroker source code, you
+   can then compile and run the program using the GridBroker jar file.
+
+---------------------------------------------------------
+Q: How do I run VisualModeler?
+
+A: To run it, just type:
+        java -jar visualmodeler.jar
+
+---------------------------------------------------------
+Q: I have the following warning message when trying to run VisualModeler.
+   Jun 29, 2003 5:36:56 PM java.util.prefs.FileSystemPreferences$3 run
+   WARNING: Could not create system preferences directory.
+            System preferences are unusable.
+
+A: That's the JDK1.4 Preferences API, used to manage system-wide and per-user
+   preferences. On Windows, the implementation uses the Windows Registry;
+   on Unix/Linux, it uses the file system.
+
+   The warning means Java (used under a user) tries to write preference files
+   in the root-owned directory that contains Java. This may be caused
+   by the way Java installed.
+
+   To solve this problem is run VisualModeler under root. Java will
+   automatically creates system preferences directory. Possibly in
+   /etc/.java/.systemPrefs
+
+   Go to the following website to know more about this:
+        http://java.sun.com/j2se/1.4.1/install-linux.html
+
+---------------------------------------------------------
+
+Q: When I tried to run code generated from VisualModeler,
+   I have the following error message:
+    Exception in thread "main" eduni.simjava.Sim_exception:
+    Sim_entity: Entity names can't contain spaces.
+        at eduni.simjava.Sim_entity.<init>(Sim_entity.java:154)
+        at gridsim.GridSim.<init>(GridSim.java:149)
+        at gridsim.GridResource.<init>(GridResource.java:93)
+        at Example1.createGridResource(Example1.java:188)
+        at Example1.main(Example1.java:57)
+
+A: GridSim Toolkit 2.2 and above now use SimJava2. SimJava2 is more strict about
+   a valid entity name compare to the previous release. Hence, to fix this
+   problem is to remove the unnecessary empty space, i.e.
+   "GridResource 0" becomes "GridResource_0"

Deleted: branches/gssim/trunk/faq.txt
===================================================================
--- branches/gssim/trunk/faq.txt	2008-08-20 13:12:31 UTC (rev 227)
+++ branches/gssim/trunk/faq.txt	2008-08-20 13:13:52 UTC (rev 228)
@@ -1,458 +0,0 @@
-# Frequently Asked Questions (FAQ)
-# Maintained by Anthony Sulistio
-# $Id: faq.txt,v 1.7 2007/09/01 02:46:01 anthony Exp $
-
-Please read this document, FAQ, examples, API, etc before contacting us.
-Moreover, look at the previous questions at the below website:
-http://sourceforge.net/mail/?group_id=94592
-
-Send any queries and feedbacks to gridsim-users @ lists.sourceforge.net
-
----------------------------------------------------------
-Q: Where can I find gridbroker, visual modeler, ... ?
-
-A: If you are looking for applications or programs built on top of GridSim,
-such as gridbroker or Visual Modeler, they can be found below:
-http://www.gridbus.org/gridsim/release.html
-
----------------------------------------------------------
-Q: I want to run the gridsim simulation on my computer but i can't because
-   Jcreator don't see the gridsim package. Please send to me the steps of
-   how compile and run the simulation.
-
-A: Go to GridSim website and there is an instruction on how to use it with
-   JCreator. http://www.gridbus.org/gridsim/paper/jcreator.pdf
-
-   If you use JBuilder or Eclipse, the instructions can be found below:
-   http://www.gridbus.org/gridsim/paper/jbuilder.pdf
-   http://www.gridbus.org/gridsim/paper/eclipse.pdf
-
----------------------------------------------------------
-Q: I would like to do some experiments for my research work on grid computing
-   using the simulator package that you have. Using the simulator,
-   can I simulate a grid environment with service providers requestors,
-   administartors etc. on a PC environment? Please pass on some resources,
-   links, and white papers and links where from I should download.
-
-Q: please help me by sending GridSim Package, give instructions and
-   also technical help to complete my project successfully.
-
-A: The best way to learn GridSim is by downloading it from below:
-   http://www.gridbus.org/gridsim/
-
-   Go through the provided examples.
-   In the website, it contains links to papers about GridSim.
-
-   As long as you have JDK version 1.4 onwards, you can run GridSim
-   on a PC. However, if you run a huge simulation, you'd probably needs
-   bigger RAM and CPU.
-
----------------------------------------------------------
-Q: Will GridSim require Globus?
-
-A: Why don't you download the GridSim toolkit and have a try?
-   Also, please read the README file.
-
----------------------------------------------------------
-Q: How do you compile and run GridSim application?
-
-A: For example, if you want to run Example1
-
-   In Unix/Linux:
-   * go to the directory of where Example1 resides, i.e.
-     at command prompt type: cd $GRIDSIM/examples/Example01
-   * to compile type:  javac -classpath $GRIDSIM/gridsim.jar:. Example1.java
-   * to run type: java -classpath gridsim.jar:. Example1
-
-   In Windows:
-   * go to the directory of where Example1 resides, i.e.
-     at command prompt type: cd %GRIDSIM%\examples\Example01
-   * to compile type:  javac -classpath %GRIDSIM%\gridsim.jar;. Example1.java
-   * to run type: java -classpath gridsim.jar;. Example1
-
-
-   The main difference is the use of ":" for Unix/Linux, and ";" for Windows
-   NOTE: $GRIDSIM or %GRIDSIM% is the location of the GridSim Toolkit package.
-         Also, inside gridsim.jar contains SimJava v2.0 classes. Hence,
-         you do not need to install SimJava libraries.
-
----------------------------------------------------------
-Q: When I run GridSim application, I have the following error message:
-        Exception in thread "main" java.lang.NoClassDefFoundError: Example1
-
-A: You need the classpath to refer to the directory where Example1.java
-   located. For Example, to run in Windows:
-        java -classpath gridsim.jar;. Example1
-
-   where Example1 is the classname you want to execute
-
----------------------------------------------------------
-Q: My GridSim application runs perfectly, however, after the end of simulation
-   it just hang without exiting properly.
-
-A: The problem may be caused by not closing GridSim entities, such as
-   GridStatistics, I/O ports, etc. Each class that extends GridSim with
-   a networked I/O ports must use terminate the I/O entities by using
-   terminateIOEntities() before exiting body() method.
-
-   Another cause for this problem is the number of Grid user entities.
-   Before the start of a GridSim application, you need to intialize the GridSim
-   package using GridSim.init(). The method requires to have the number of
-   Grid user entities. If the number is different from the actual Grid user
-   entities, your GridSim application will hang or can't exit properly.
-
----------------------------------------------------------
-Q: I am creating a network topology using GridSim. When I run the experiment,
-I have the following exception message:
-
-java.lang.NullPointerException
-   at gridsim.net.RIPRouter.getScheduler(RIPRouter.java:451)
-   at gridsim.net.RIPRouter.getScheduler(RIPRouter.java:401)
-   at gridsim.net.RIPRouter.processNetPacket(RIPRouter.java:302)
-   at gridsim.net.RIPRouter.processEvent(RIPRouter.java:270)
-   at gridsim.net.Router.body(Router.java:267)
-   at eduni.simjava.Sim_entity.run(Sim_entity.java:603)
-
-A: Network exception message is generally caused by 2 things:
-- If you created a new router or link entity, it hasn't been registered to
-GridInformationService class; OR
-
-- GridSim needs few seconds for all network entities to be registered and
-for the network entity to fill in its routing table dynamically.
-Currently, GridSim uses a flooding approach for locating the neighbour
-routers. Hence, these routers need time to receive all the replies.
-I think this could be the main cause of the exception message.
-
----------------------------------------------------------
-Q: When running GridSim Example 4, 5 and 6 I got an infinite loop
-   saying: "Waiting to get list of resources".
-
-A: In GridSim 2.1, GridSim.getGridResourceList() uses a message event
-   to tell GIS (GridInformationService) entity to send the GridResource
-   list. This causes a significant delay and a bit redundant.
-
-   In GridSim 2.2, GridSim.getGridResourceList() directly uses a
-   method call to GIS entity rather than a message passing.
-   This makes the operation a lot faster. However, during the early stage
-   of simulation, a GridResource might be slow in registering its service
-   to GIS. Hence, the GridResource list is always empty and causing
-   an infinite loop.
-
-   To solve this problem, inside the while() loop, put the following
-   code:
-            // need to pause for a while to wait GridResources finish
-            // registering to GIS
-            super.gridSimHold(1.0);    // hold by 1 second
-
-   So, you wait 1 second later to get GridResource list.
-
----------------------------------------------------------
-Q: When I tried to run GridSim Example4, I have the following error message:
-    java.lang.IncompatibleClassChangeError
-        at Example4.body(Example4.java:70)
-        at eduni.simjava.Sim_entity.run(Sim_entity.java:603)
-
-A: I am not sure what is the exact problem. However, this is mainly
-   caused by older release of SimJava. GridSim Toolkit 2.2 and above now use
-   SimJava2. Simply recompile the Example4.java will solve this
-   problem.
-
-   NOTE: This problem is also effected GridSim Example6.
-
----------------------------------------------------------
-Q: When I tried to run GridSim Example1, I have the following error message:
-    Exception in thread "main" eduni.simjava.Sim_exception:
-    Sim_entity: Entity names can't contain spaces.
-        at eduni.simjava.Sim_entity.<init>(Sim_entity.java:154)
-        at gridsim.GridSim.<init>(GridSim.java:149)
-        at gridsim.GridResource.<init>(GridResource.java:93)
-        at Example1.createGridResource(Example1.java:188)
-        at Example1.main(Example1.java:57)
-
-A: GridSim Toolkit 2.2 and above now use SimJava2. SimJava2 is more strict about
-   a valid entity name compare to previous release. Hence, to fix this
-   problem is to remove the unnecessary empty space, i.e.
-   "GridResource 0" becomes "GridResource_0"
-
----------------------------------------------------------
-Q: Are there any type of applications that I can simulate with GridSim?
-
-A: GridSim provides the grid simulation environment (with resources and
-   users), but you need to write codes specifically for the application you
-   want to simulate, e.g. a resource broker Nimrod/G is written to call
-   GridSim classes.
-
----------------------------------------------------------
-Q: How do I create Gridlets with compute I/O requirements?
-
-A: Gridlets with compute I/O requirements are simulated through their file
-   sizes (input) and output sizez (output) parameters.
-   See Figure 16 of the GridSim paper.
-
----------------------------------------------------------
-Q: I have a question on network simulation in Gridsim.
-   In my understanding, entities with networking capability must define
-   input and output port. Both ports are "connected" to a simulated network.
-   How does Gridsim models network link and its characteristics, especially
-   bandwidth, since I couldn't find class that models this network link?
-   Does Gridsim also simulate bandwidth-sharing if there are several IOdata
-   are sent using the same link?
-
-A: Not supported in the older versions. Currently GridSim uses very
-   simple network model.
-
-   Since GridSim ver3.1, it has a realistic network model. However,
-   advanced network features are not supported.
-
----------------------------------------------------------
-Q: Is GridSim tool kit provides any help in solving problems for dynamical
-   resource allocation upon failure?
-
-A: GridSim provides mechanism to reserve, but policy of reservation and
-   how to handle failures etc. is up to server's provider and consumers
-   to define.
-
----------------------------------------------------------
-Q: How do you model the gridlet execution in time_shared resource?
-
-A: Just creating a Gridlet is sufficient. It runs on both time and space
-   shared machines.
-
----------------------------------------------------------
-Q: Does each gridlet can only be processed by only one PE?
-
-A: For older GridSim versions, it runs one PE.
-   Since GridSim ver3.0, each Gridlet can ask to be run on multiple PEs.
-   However, it is up to the scheduler to handle this.
-   At the moment, by default, TimeShared and SpaceShared scheduler executes
-   an incoming Gridlet to only 1 PE.
-
----------------------------------------------------------
-Q: Is the model for parallel job included inside the GridSim?
-
-A: It is up users to model parallel application job at the higher level
-   (develop on top of gridsim).
-
----------------------------------------------------------
-Q: When I run GridSim, I have the following error message:
-        Sim_system:Error - past event detected!
-        Time: 0.0, event time: -XXXXX.X event type: 1
-        Where XXXXX.X is a negative number that varies.
-
-A: It appears like this error comes up for one of the following scenarios:
-   - an entity or object waits for a specific event. However, the response
-     event type is different.
-   - some events are not captured.
-   - GridSim runs under multi-threaded environment. Hence, some events might
-     be accidentally deleted or being changed by other thread to wait for
-     a different response that doesn't exist, etc ...
-
----------------------------------------------------------
-Q: Does GridSim currently support the usage of any wireless network standard
-when specifying network topology?
-
-A: No. We have NOT done so much about wireless network support in GridSim.
-   But if you are willing, we could explore this with you.
-
----------------------------------------------------------
-Q: Does GridSim support multiple simulations or runs in a single program?
-
-A: No. Currently, GridSim only allows a single experiment to run in a main()
-   method. Hence, to calculate a confidence interval, you need to do this
-   manually.
-
----------------------------------------------------------
-Q: Does GridSim run in a cluster or a PC?
-
-A: GridSim runs in a PC as a stand-alone program with multiple threads.
-   This means if you want to run in a cluster, you just need to request 1 node.
-
----------------------------------------------------------
-Q: I came across three variables: peak load, off-peak load and holiday load.
-   I understand from the study I have done that these variables represent
-   the load factor. I do not fully get what this means and was hoping that
-   you could help me out so I can progress further with my work.
-
-A: These load factors are influencing the total execution time
-   of a job in a given resource.
-   If you set these loads to zero, means this resource is idle / free.
-   If you want to write a resource scheduler, like SpaceShared or TimeShared
-   then these load factors are important.
-
----------------------------------------------------------
-Q: for the Gridlet class, what are the units of file size, length, and output?
-
-A: the unit of file size and output is in byte.
-   For the Gridlet length, the unit is in MI (Millions Instructions).
-   A CPU clock is measured in MIPS (Millions Instructions Per Second) as
-   suggested by SPEC.
-
----------------------------------------------------------
-Q: In the previous releases of GridSim you had to use
-GridSim class to send messages to other entities. The provided "send" methods
-included a parameter to indicate the sender of the request. It is no clear how
-to indicate this with the "send" methods provided by the GridSimCore class. The
-lack of ID information in the event raises an exception in the GridResource
-class. Reading the source code of the GridResource class I've realized that the
-way to send the ID of the sender could be the following:
-
-super.send(resourceId, GridSimTags.SCHEDULE_NOW,
-GridSimTags.RESOURCE_CHARACTERISTICS, new Integer(this.get_id()));
-
-This solves the first problem but generates a new exception in other class:
-Exception in thread "Thread-7" java.lang.ArrayIndexOutOfBoundsException: -1
-       at java.util.ArrayList.get(ArrayList.java:323)
-       at eduni.simjava.Sim_system.send(Sim_system.java:600)
-       at eduni.simjava.Sim_entity.sim_schedule(Sim_entity.java:342)
-       at gridsim.net.Output.defaultSend(Unknown Source)
-       at gridsim.net.Output.body(Unknown Source)
-       at eduni.simjava.Sim_entity.run(Sim_entity.java:603)
-
-I've read the source of the Output class, but I've not found a solution to the
-problem. Do you know where can be the problem?
-
-A: The problem was in the "baudRate" attribute that wasn't initialized.
-So using GridSim(String name, double baudRate) the problem was solved.
-
----------------------------------------------------------
-
-
-
-Questions related to GridBroker
-===============================
-
-Q: How do you compile and run GridBroker application?
-
-A: Similar to compile and to run GridSim. Instead of using gridsim.jar,
-   you use gridbroker.jar. Inside this jar file, it contains GridBroker,
-   GridSim and SimJava classes.
-
-   Please do not use recent GridSim release jar file when running this broker
-   (see the below question).
-
----------------------------------------------------------
-Q: I have executed all gridsim examples. But while executing gridbroker
-i.e C:\gridsimtoolkit-4.0\application\gridbroker\example\Example1.java
-it gives following error after initializing gridsim:
-
-Initialising...
-Starting GridSim version 4.0
-Entities started.
-java.lang.IncompatibleClassChangeError
- at gridbroker.Broker.body( Broker.java:649)
- at eduni.simjava.Sim_entity.run(Sim_entity.java:603)
-
-
-A: read the README.txt file located under $GRIDSIM/application/gridbroker.
-./gridbroker.jar  - A jar file containing GridBroker, GridSim v2.1, and
-                    SimJava v1.2 classes.
-NOTE: No updates or improvements on GridBroker package since GridSim v2.1,
-hence, it is more stable under GridSim v2.1 and SimJava v1.2 release.
-
-You cant mixed up jars from different class versions.
-That's why you have this error message.
-
----------------------------------------------------------
-Q: I want to create a specific application. Is it necessary to build on top
-   of GridBroker?
-
-A: You are expected to develop an application on top of GridSim,
-   instead of GridBroker. GridBroker is included to demonstrate the
-   capability of GridSim in simulating the Grid environment and a
-   Nimrod/G like deadline and budget constraint scheduling system.
-
----------------------------------------------------------
-Q: The application generates the files: tracefile, stat.txt, g14.sched1,
-   g14.sched2, g14.sched3, g14.sched31, g14.sched4, g14.sched5, g14.sched6.
-   What are the meaning of these files?
-
-A: These files contains statistical results of the simulation that are of
-   interest to the GridSim user (ie. you).
-
-   When running a GridBroker application, it will produce the following files:
-
-        stat.txt -> created by GridSim class during GridSim.init() to create
-                    a GridStatistics object for statistical purposes
-
-        tracefile -> created by the SimJava package to trace every events
-                     that are performed by SimJava, GridSim and GridBroker
-                     during the simulation.
-
-        g14.sched* -> All of these files are created by Broker class.
-                      When we create an UserEntity object, it will
-                      automatically creates a Broker object.
-
-    Description on the g14.sched* files:
-        g14.sched1 is about Gridlets finished report.
-        g14.sched2 is about Gridlets processing expenses report.
-        g14.sched3 is about Gridlets on resource report.
-        g14.sched31 is about Gridlets committed for resource report.
-        g14.sched4 is same as g14.sched1, however this file only
-            displays the overall result or summary of g14.sched1 file.
-
-        g14.sched5 is same as g14.sched2, however this file only
-            displays the overall result or summary of g14.sched2 file.
-
-        g14.sched6 is same as g14.sched3, however this file only
-            displays the overall result or summary of g14.sched3 file.
-
-    NOTE: Explanations about the content of each file are mentioned in
-          GridBroker example section.
-
----------------------------------------------------------
-
-
-Questions related to VisualModeler
-==================================
-
-
-Q: What is VisualModeler (VM)?
-
-A: It is a program that generates GridBroker source code.
-   With VM, you can specify how many grid users and resources for your
-   simulation. After finish generating the GridBroker source code, you
-   can then compile and run the program using the GridBroker jar file.
-
----------------------------------------------------------
-Q: How do I run VisualModeler?
-
-A: To run it, just type:
-        java -jar visualmodeler.jar
-
----------------------------------------------------------
-Q: I have the following warning message when trying to run VisualModeler.
-   Jun 29, 2003 5:36:56 PM java.util.prefs.FileSystemPreferences$3 run
-   WARNING: Could not create system preferences directory.
-            System preferences are unusable.
-
-A: That's the JDK1.4 Preferences API, used to manage system-wide and per-user
-   preferences. On Windows, the implementation uses the Windows Registry;
-   on Unix/Linux, it uses the file system.
-
-   The warning means Java (used under a user) tries to write preference files
-   in the root-owned directory that contains Java. This may be caused
-   by the way Java installed.
-
-   To solve this problem is run VisualModeler under root. Java will
-   automatically creates system preferences directory. Possibly in
-   /etc/.java/.systemPrefs
-
-   Go to the following website to know more about this:
-        http://java.sun.com/j2se/1.4.1/install-linux.html
-
----------------------------------------------------------
-
-Q: When I tried to run code generated from VisualModeler,
-   I have the following error message:
-    Exception in thread "main" eduni.simjava.Sim_exception:
-    Sim_entity: Entity names can't contain spaces.
-        at eduni.simjava.Sim_entity.<init>(Sim_entity.java:154)
-        at gridsim.GridSim.<init>(GridSim.java:149)
-        at gridsim.GridResource.<init>(GridResource.java:93)
-        at Example1.createGridResource(Example1.java:188)
-        at Example1.main(Example1.java:57)
-
-A: GridSim Toolkit 2.2 and above now use SimJava2. SimJava2 is more strict about
-   a valid entity name compare to the previous release. Hence, to fix this
-   problem is to remove the unnecessary empty space, i.e.
-   "GridResource 0" becomes "GridResource_0"


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