Well, not really I think - as tasks _are_ our asynchroneous operations.

No, they are not. We have: - synchronous operation - asynchronous operation ; starts immediately - task creating operation ; needs explicit start My suggestion is to remove the tasks, and put everything useful from the task interface into the job interface. And do async operations by async operations. Thilo -- Thilo Kielmann http://www.cs.vu.nl/~kielmann/

I am actually in favour removing the concept of "tasks" from the SAGA spec. It simply creates intellectual overhead. (Remember people keep asking about the difference of tasks and jobs??)

...

- synchronous operation - asynchronous operation ; starts immediately - task creating operation ; needs explicit start

Both of the latter calls return a task handle (or call it async op handle), that why, in SAGA, they are esentially the same.

so, call it async handle

Well, our point is really that everythin usful from task should go into the job interface (job should implement task).

So, maybe you are actually in violent agreement, kind of? :-) Somwhoe I doubt it :-P

violent, at least -- agreement, maybe? Thilo -- Thilo Kielmann http://www.cs.vu.nl/~kielmann/

Hi, I just had a discussion with Thilo about the topic, as he and me obviously talked somewhat orthogonal to each other... Well, now we have the same opinion, kind of, and I have barely any bruises... Anyway, I want to summarize our point here, as I probably was not really clear in my initial post. Sorry if re-iteration of the topic bores you... So, we have tasks, which represent async operations, with a couple of states attached, and the ability to call run(), wait() and cancel() on these. And we can collect them in containers, and wait() on many of these tasks conveniently. And then we have jobs, which represent remote executables, with a couple of states attached, and the ability to call run (== create them), wait() and cancel(). And some more methods. And we can't collect them in containers right now, but would like to. You see the similarities, right? Its even more obvious in code: Tasks: -------------------------------------------- task_container tc; task t = file.copy saga::task (...); t.run ( ); t.wait (1.0); tc.add (t); tc.wait ( ); -------------------------------------------- Jobs: -------------------------------------------- job_container jc; job j = job_server.submit (job_descr); j.wait (1.0); jc.add (j); jc.wait ( ); -------------------------------------------- slightly changed: -------------------------------------------- job_container jc; ! job j = job_server.create (job_descr); + j.run ( ); j.wait (1.0); jc.add (j); jc.wait ( ); -------------------------------------------- The similarities are obvious I think. Now, if job would IMPLEMENT the task interface (or inherit from task), we would unify both classes, and hence: - simplify jobs (leave only those methods which are specific to jobs, like migrate, signal, ... - allow to out jobs into task containers, efficiently handling large amounts of jobs and other tasks - have the API and used paradigms more uniform. Also, if later tasks get suspendable, as Gregor rightly suggested, we can move more methods to tasks, w/o breaking the paradigms. In terms of state, following mappings would be appropriate: job::Pending -> task::Pending job::Done -> task::Done job::Failed -> task::Failed job::??? -> task::Cancelled job::Queued,Running,Pre/Poststaging,... -> task::Running So, no adjustements to the statet models are needed AFAICS, apart from Cancelled (Does it make sense on jobs? Should job::stop be job::cancel? Should tasks::cancel be task::job?) Hope that clearifies things. I think Gregor was on target with his remarks, and Hartmut signalled consent as well. And I think I convinced Thilo (Andre rubs his bruises). Unless there is any opposition, I'll go ahead and document that in the strawman then, ok? Cheers, Andre. Quoting [Thilo Kielmann] (Feb 04 2006):

Date: Sat, 4 Feb 2006 22:29:41 +0100 From: Thilo Kielmann To: saga-rg@ggf.org Subject: Re: [saga-rg] tasks and jobs...

...

Wouldn't it be useful to have jobs implementing the task interface?

Certainly, no. Jobs and Tasks are two different things, and they are this on purpose.

However, Tasks always have been the mechanism for asynchronous operation, which is kind-of obsoleted by having asynchronous ops directly.

If you want to work on the "S" of SAGA: why not unify both Tasks and Jobs into a better "Job" notion, and do local asynchronous operations via async, local calls?

Thilo -- "So much time, so little to do..." -- Garfield

Andre, I have a couple of reservations about this action that you may be able to answer. I had been hoping to avoid implementing the 'Task' namespace in the java bindings and encourage developers to use the language's support to threading to allow asynchronous method calls in the client code. I am therefore concerned about creating a dependency between the 'JobManagement' namespace and the 'Task' namespace. The submission of remote jobs is naturally asynchronous, and there are natural semantic parallels to the asynchronous model described by the 'Task' namespace. However from my reading of the API I understood these two models to be independent in purpose; creating a dependency could hinder the natural description (and development) of these two areas of the API. The idea of a job container for the management of a large number of remote jobs is useful. However the TaskContainter does not appear to be wholly compatible; the run() method to start the asynchronous operations is unnecessary for jobs that have been submitted to a remote resource. Graeme Quoting Andre Merzky :

Hi,

I just had a discussion with Thilo about the topic, as he and me obviously talked somewhat orthogonal to each other...

Well, now we have the same opinion, kind of, and I have barely any bruises... Anyway, I want to summarize our point here, as I probably was not really clear in my initial post.

Sorry if re-iteration of the topic bores you...

So, we have tasks, which represent async operations, with a couple of states attached, and the ability to call run(), wait() and cancel() on these. And we can collect them in containers, and wait() on many of these tasks conveniently.

And then we have jobs, which represent remote executables, with a couple of states attached, and the ability to call run (== create them), wait() and cancel(). And some more methods. And we can't collect them in containers right now, but would like to.

You see the similarities, right? Its even more obvious in code:

Tasks: -------------------------------------------- task_container tc; task t = file.copy saga::task (...); t.run ( ); t.wait (1.0);

tc.add (t); tc.wait ( ); --------------------------------------------

Jobs: -------------------------------------------- job_container jc; job j = job_server.submit (job_descr); j.wait (1.0);

jc.add (j); jc.wait ( ); --------------------------------------------

slightly changed: -------------------------------------------- job_container jc; ! job j = job_server.create (job_descr); + j.run ( ); j.wait (1.0);

jc.add (j); jc.wait ( ); --------------------------------------------

The similarities are obvious I think. Now, if job would IMPLEMENT the task interface (or inherit from task), we would unify both classes, and hence:

- simplify jobs (leave only those methods which are specific to jobs, like migrate, signal, ...

- allow to out jobs into task containers, efficiently handling large amounts of jobs and other tasks

- have the API and used paradigms more uniform.

Also, if later tasks get suspendable, as Gregor rightly suggested, we can move more methods to tasks, w/o breaking the paradigms.

In terms of state, following mappings would be appropriate:

job::Pending -> task::Pending job::Done -> task::Done job::Failed -> task::Failed job::??? -> task::Cancelled

job::Queued,Running,Pre/Poststaging,... -> task::Running

So, no adjustements to the statet models are needed AFAICS, apart from Cancelled (Does it make sense on jobs? Should job::stop be job::cancel? Should tasks::cancel be task::job?)

Hope that clearifies things. I think Gregor was on target with his remarks, and Hartmut signalled consent as well. And I think I convinced Thilo (Andre rubs his bruises).

Unless there is any opposition, I'll go ahead and document that in the strawman then, ok?

Cheers, Andre.

Quoting [Thilo Kielmann] (Feb 04 2006):

...

Date: Sat, 4 Feb 2006 22:29:41 +0100 From: Thilo Kielmann To: saga-rg@ggf.org Subject: Re: [saga-rg] tasks and jobs...

...

Wouldn't it be useful to have jobs implementing the task interface?

Certainly, no. Jobs and Tasks are two different things, and they are this on purpose.

However, Tasks always have been the mechanism for asynchronous operation, which is kind-of obsoleted by having asynchronous ops directly.

If you want to work on the "S" of SAGA: why not unify both Tasks and Jobs into a better "Job" notion, and do local asynchronous operations via async, local calls?

Thilo -- "So much time, so little to do..." -- Garfield

Andre, The benefits of the application of the TaskContainer semantics to job submission are compelling. Whilst the separation of JobService.submitJob() into JobService.create() and Job.run() methods adds a little complexity, the possibility of optimised bulk operations may justify this. The role of the JobService changes a little, it may be used to create Job objects without submitting them to the resource manager. Will JobService.runJob() invoke the Job object that has been submitted to the resource manager? --- I am yet to be convinced that the 'Task' and 'JobManagement' namespaces should be linked. Whilst the semantics of these namespaces are similar they are designed for different purposes; a simple model of asynchronous method calls in the client, and the submission of batch jobs to a remote resource. The advantage of keeping these two namespaces separate is to avoid an unnecessary dependency between these two different areas of the API. For example; if in the future additional methods are required to support asynchronous method calls these would be reflected in the JobManagement package. [Or if the Task namespace were altered to support language specific features, see below] The advantage of linking the namespaces would be to allow all classes implementing TaskContainer to handle Job objects. --- In Java the basis for multithreading support is sub-classing the java.lang.Thread class (or implementing the java.lang.Runnable interface). In practice SAGA implementations could return inner classes that may be called asynchronously (by either of these approaches) for each API method. This is essentially the whole story (prior to Java 5.0), and the whole approach could be encapsulated within the SAGA.Task model. The problem with encapsulation within the SAGA.Task model is that the fine-grain control over the threads (when sub-classing java.lang.Thread) is lost. Furthermore when using Java 5.0 it would not be possible to leverage the high-level concurrency utilities now available (java.util.concurrent.*). For example the task scheduling framework would be appropriate to control the execution of the threads. For more details see: http://java.sun.com/docs/books/tutorial/essential/threads/index.html In C# the model is nicer than in Java. Methods may be invoked asynchronously by creating a 'delegate' for that method using Thread.ThreadStart. Evaluation of the delegates in different threads can be managed at a high-level via the thread pool. When working with these languages it there will be some functionality that it will be important not to preclude. In Java <5.0 there may be little above and beyond that which is available in SAGA.Task of value to most users, and encapsulation may be the correct approach. However the high-level support for concurrency available in Java 5.0 and C# is certainly important. I am unsure whether access to this functionality is best achieved by by-passing, or altering SAGA.Task namespace in the language bindings. Graeme Quoting Andre Merzky :

Hi Graeme,

Quoting [G.E.POUND@soton.ac.uk] (Feb 06 2006):

...

Andre,

I have a couple of reservations about this action that you may be able

to

...

answer.

I had been hoping to avoid implementing the 'Task' namespace in the java bindings and encourage developers to use the language's support to threading to allow asynchronous method calls in the client code.

I understood that much from your last comments, but my limited knowledge does not allow me to give a qualified answer I'm afraid. Hmm, maybe we can work this out together :-)

Could you post some code examples to demonstrate how a asynchronous seek (for example) would be coded in a java application?

The C++ code would be:

saga::file f (url); saga::task t = f.seek saga::task (off, whence, &pos);

t.run (); t.wait ();

Next question is, how would a java application manage many tasks - i.e. is there something similar to a saga::task_container ?

saga::task_container tc;

tc.add (task_1); tc.add (task_2); tc.add (task_3);

tc.run (); tc.wait ();

...

I am therefore concerned about creating a dependency between the 'JobManagement' namespace and the 'Task' namespace.

I think, for the java bindings that would mean that job implements the task interface. Apart from the run you mention below, the semantic of the task interface is actually included in job already, more or less, only the methods and states are differently named (that is one motivation for the proposal really).

...

The submission of remote jobs is naturally asynchronous, and there are natural semantic parallels to the asynchronous model described by the 'Task' namespace. However from my reading of the API I understood these two models to be independent in purpose; creating a dependency could hinder the natural description (and development) of these two areas of the API.

Both models are not really different on purpose. Would you see an advantage of having them truly separate?

...

The idea of a job container for the management of a large number of

remote

...

jobs is useful. However the TaskContainter does not appear to be wholly compatible; the run() method to start the asynchronous operations is unnecessary for jobs that have been submitted to a remote resource.

You are right. Well, that might be somewhat subtle, but in the example code below, the submit_job() call is accompanied by c new reate_job(). That creates a job which needs to be run(), which would make it compatiple to the task model.

saga::job j1 = job_server.create_job (jd); // job state is 'pending'

j1.run (); // job state is 'running' or so - 'not pending'

j1.wait (); // job state is Done or Failed

saga::job j2 = job_server.submit_job (jd); // job state is 'running' or so - 'not pending'

j1.wait (); // job state is Done or Failed

That is very similar to the semantics we have for tasks...

One reason for this proposal is additionally that we want to approach the bulk operations soon. Consider a parameter sweep, where 100.000 jobs are to be run.

for ( i = 0; i < 100.000; i++ ) { jobs[i] = job_server.submit (jd[i]); // SUBMIT }

for ( i = 0; i < 100.000; i++ ) { jobs[i].wait (); }

As for each submission, you are very likely to have at least one remote operation (they are independend), that will take a lot of time.

Compare that to:

task_container tc;

for ( i = 0; i < 100.000; i++ ) { tc.add (job_server.create (jd[i])); // CREATE }

tc.run (); tc.wait ();

It is rather straigh forward to optimize the task container for bulk job submission, or bulk operations in general (we hope).

What I am not sure is, what would that look like in native java? Are there similar mechanisms?

Looking forward to your comments,

Andre.

...

Graeme

Quoting Andre Merzky :

...

Hi,

I just had a discussion with Thilo about the topic, as he and me obviously talked somewhat orthogonal to each other...

Well, now we have the same opinion, kind of, and I have barely any bruises... Anyway, I want to summarize our point here, as I probably was not really clear in my initial post.

Sorry if re-iteration of the topic bores you...

So, we have tasks, which represent async operations, with a couple of states attached, and the ability to call run(), wait() and cancel() on these. And we can collect them in containers, and wait() on many of these tasks conveniently.

And then we have jobs, which represent remote executables, with a couple of states attached, and the ability to call run (== create them), wait() and cancel(). And some more methods. And we can't collect them in containers right now, but would like to.

You see the similarities, right? Its even more obvious in code:

Tasks: -------------------------------------------- task_container tc; task t = file.copy saga::task (...); t.run ( ); t.wait (1.0);

tc.add (t); tc.wait ( ); --------------------------------------------

Jobs: -------------------------------------------- job_container jc; job j = job_server.submit (job_descr); j.wait (1.0);

jc.add (j); jc.wait ( ); --------------------------------------------

slightly changed: -------------------------------------------- job_container jc; ! job j = job_server.create (job_descr); + j.run ( ); j.wait (1.0);

jc.add (j); jc.wait ( ); --------------------------------------------

The similarities are obvious I think. Now, if job would IMPLEMENT the task interface (or inherit from task), we would unify both classes, and hence:

- simplify jobs (leave only those methods which are specific to jobs, like migrate, signal, ...

- allow to out jobs into task containers, efficiently handling large amounts of jobs and other tasks

- have the API and used paradigms more uniform.

Also, if later tasks get suspendable, as Gregor rightly suggested, we can move more methods to tasks, w/o breaking the paradigms.

In terms of state, following mappings would be appropriate:

job::Pending -> task::Pending job::Done -> task::Done job::Failed -> task::Failed job::??? -> task::Cancelled

job::Queued,Running,Pre/Poststaging,... -> task::Running

So, no adjustements to the statet models are needed AFAICS, apart from Cancelled (Does it make sense on jobs? Should job::stop be job::cancel? Should tasks::cancel be task::job?)

Hope that clearifies things. I think Gregor was on target with his remarks, and Hartmut signalled consent as well. And I think I convinced Thilo (Andre rubs his bruises).

Unless there is any opposition, I'll go ahead and document that in the strawman then, ok?

Cheers, Andre.

...

Date: Sat, 4 Feb 2006 22:29:41 +0100 From: Thilo Kielmann To: saga-rg@ggf.org Subject: Re: [saga-rg] tasks and jobs...

...

Wouldn't it be useful to have jobs implementing the task interface?

Certainly, no. Jobs and Tasks are two different things, and they are this on

Quoting [Thilo Kielmann] (Feb 04 2006): purpose.

...

However, Tasks always have been the mechanism for asynchronous

operation,

...

which is kind-of obsoleted by having asynchronous ops directly.

If you want to work on the "S" of SAGA: why not unify both Tasks and Jobs into a better "Job" notion, and do local asynchronous operations via async, local calls?

Thilo -- "So much time, so little to do..." -- Garfield

-- "So much time, so little to do..." -- Garfield

Andre, Sure, no problem. Here are two examples of how asynchronous support could be provided in the Java bindings. The first completely encapsulates threading within the SAGA.Task model, the second exposes more of the threading capabilities. #1 Encapsulated threading model Following the syntax of the SAGA.Task model, the task factory will return objects implementing the Task interface for each of the Directory methods. //Example #1 DirectoryTaskFactory dtf = dir.createTaskFactory (); Task t1 = dtf.ls (dir); t1.run (); In this example when the method run() is invoked a thread is created and started internally by the object t1. Inner classes could also be used to conceal the gruesome details of this. All management of the state of the thread must be via the Task interface. This is fine as this is the purpose of the Task interface, particularly at the level at which the user programs. However the problem comes when the more detailed control over the thread is required, this is may be required by more sophisticated implementations of TaskContainer. #2 Exposed threading model If we need to expose fine-grained control over the threading model in the Java bindings it would be necessary to change the SAGA.Task namespace. //Example #2 DirectoryTaskFactory dtf = dir.createTaskFactory (); java.lang.Thread t1 = dtf.ls (dir); t1.start (); //Or t1.run(); TaskContainer tc; tc.addTask (t1); Through this approach the interface exposed to the user is more complex, however the TaskContainer may be more powerful. Implementations based in Java 5.0 can use the high level concurrency utilities to control the threads efficiently (and safely?). This approach would require the Task namespace to be specific to asynchronous method invocation, and preclude any link to the JobManagement namespace - but, of course, I do not think that this is a problem. A similar situation exists in C# in which 'tasks' could be returned as delegates or threads to facilitate the use of high-level threading support in the language; include the thread pool. --- Of course it is a tangential issue about the hazards of invoking these methods asynchronously. For example, the developer of a Java implementation should ensure that asynchronous methods synchronize properly. Also the example of the asynchronous methods called on a SAGA directory can easily be used to illustrate the potential issues arising from calling operations that move and copy the contents of a directory. ie: // Create Task factories DirectoryTaskFactory dtf = dir.createTaskFactory (); // Create Tasks Task t1 = dtf.ls (result); Task t2 = dtf.copy (source,target); Task t3 = dtf.move (source,target); With no control about the order of these operations a user of the SAGA API could quickly write very unsafe code. Graeme Andre Merzky wrote:

Hi Graeme,

thanks for the pointer!

I still have some questions if you don't mind...

What I have seen at the URL you sent is how to program threads in Java. What I am unsure about is, what would a Java-SAGA programmer actually _do_.

For example, if he wants to do a async seek on a file, what would he do?

Lets try:

- Create a new class which is 'Runnable', and inherits 'saga::file' - implement 'run' to perform a seek

Can't be, because run is void (or can you change that?)

try again:

- Create a new class which is 'Runnable', and inherits 'saga::file' - have seek not doing anything, but setting args - have run perform the seek async

Hmm, again not nice, as your object needs to be very stateful: e.g. store args for many reads, which are later run

try again:

- saga::file is already 'Runnable' - no, wait, it still has only one 'run' method, so I can't do a async seek and then async read...

You see, I am really on the wrong track - sorry, this looks probably very foolish to you...

I would very much appreciate a code example. That usualoly helps me most :-)

I will google somewhat, I am sure there are for example async file classes around or so..

Thanks, Andre.

Quoting [G.E.POUND@soton.ac.uk] (Feb 07 2006):

...

Date: Tue, 7 Feb 2006 14:33:34 +0000 From: G.E.POUND@soton.ac.uk To: Andre Merzky Cc: G.E.POUND@soton.ac.uk, Thilo Kielmann , saga-rg@ggf.org Subject: Re: [saga-rg] tasks and jobs...

Andre,

The benefits of the application of the TaskContainer semantics to job submission are compelling. Whilst the separation of JobService.submitJob() into JobService.create() and Job.run() methods adds a little complexity, the possibility of optimised bulk operations may justify this.

The role of the JobService changes a little, it may be used to create Job objects without submitting them to the resource manager. Will JobService.runJob() invoke the Job object that has been submitted to the resource manager?

---

I am yet to be convinced that the 'Task' and 'JobManagement' namespaces should be linked. Whilst the semantics of these namespaces are similar they are designed for different purposes; a simple model of asynchronous method calls in the client, and the submission of batch jobs to a remote resource.

The advantage of keeping these two namespaces separate is to avoid an unnecessary dependency between these two different areas of the API. For example; if in the future additional methods are required to support asynchronous method calls these would be reflected in the JobManagement package. [Or if the Task namespace were altered to support language specific features, see below]

The advantage of linking the namespaces would be to allow all classes implementing TaskContainer to handle Job objects.

---

In Java the basis for multithreading support is sub-classing the java.lang.Thread class (or implementing the java.lang.Runnable interface). In practice SAGA implementations could return inner classes that may be called asynchronously (by either of these approaches) for each API method. This is essentially the whole story (prior to Java 5.0), and the whole approach could be encapsulated within the SAGA.Task model.

The problem with encapsulation within the SAGA.Task model is that the fine-grain control over the threads (when sub-classing java.lang.Thread) is lost. Furthermore when using Java 5.0 it would not be possible to leverage the high-level concurrency utilities now available (java.util.concurrent.*). For example the task scheduling framework would be appropriate to control the execution of the threads.

For more details see: http://java.sun.com/docs/books/tutorial/essential/threads/index.html

In C# the model is nicer than in Java. Methods may be invoked asynchronously by creating a 'delegate' for that method using Thread.ThreadStart. Evaluation of the delegates in different threads can be managed at a high-level via the thread pool.

When working with these languages it there will be some functionality that it will be important not to preclude. In Java <5.0 there may be little above and beyond that which is available in SAGA.Task of value to most users, and encapsulation may be the correct approach. However the high-level support for concurrency available in Java 5.0 and C# is certainly important. I am unsure whether access to this functionality is best achieved by by-passing, or altering SAGA.Task namespace in the language bindings.

Graeme

Quoting Andre Merzky :

...

Hi Graeme,

...

Andre,

I have a couple of reservations about this action that you may be able to answer.

I had been hoping to avoid implementing the 'Task' namespace in the java bindings and encourage developers to use the language's support to threading to allow asynchronous method calls in the client code. I understood that much from your last comments, but my

Quoting [G.E.POUND@soton.ac.uk] (Feb 06 2006): limited knowledge does not allow me to give a qualified answer I'm afraid. Hmm, maybe we can work this out together :-)

Could you post some code examples to demonstrate how a asynchronous seek (for example) would be coded in a java application?

The C++ code would be:

saga::file f (url); saga::task t = f.seek saga::task (off, whence, &pos);

t.run (); t.wait ();

Next question is, how would a java application manage many tasks - i.e. is there something similar to a saga::task_container ?

saga::task_container tc;

tc.add (task_1); tc.add (task_2); tc.add (task_3);

tc.run (); tc.wait ();

...

I am therefore concerned about creating a dependency between the 'JobManagement' namespace and the 'Task' namespace. I think, for the java bindings that would mean that job implements the task interface. Apart from the run you mention below, the semantic of the task interface is actually included in job already, more or less, only the methods and states are differently named (that is one motivation for the proposal really).

...

The submission of remote jobs is naturally asynchronous, and there are natural semantic parallels to the asynchronous model described by the 'Task' namespace. However from my reading of the API I understood these two models to be independent in purpose; creating a dependency could hinder the natural description (and development) of these two areas of the API. Both models are not really different on purpose. Would you see an advantage of having them truly separate?

...

The idea of a job container for the management of a large number of remote jobs is useful. However the TaskContainter does not appear to be wholly compatible; the run() method to start the asynchronous operations is unnecessary for jobs that have been submitted to a remote resource. You are right. Well, that might be somewhat subtle, but in the example code below, the submit_job() call is accompanied by c new reate_job(). That creates a job which needs to be run(), which would make it compatiple to the task model.

saga::job j1 = job_server.create_job (jd); // job state is 'pending'

j1.run (); // job state is 'running' or so - 'not pending'

j1.wait (); // job state is Done or Failed

saga::job j2 = job_server.submit_job (jd); // job state is 'running' or so - 'not pending'

j1.wait (); // job state is Done or Failed

That is very similar to the semantics we have for tasks...

One reason for this proposal is additionally that we want to approach the bulk operations soon. Consider a parameter sweep, where 100.000 jobs are to be run.

for ( i = 0; i < 100.000; i++ ) { jobs[i] = job_server.submit (jd[i]); // SUBMIT }

for ( i = 0; i < 100.000; i++ ) { jobs[i].wait (); }

As for each submission, you are very likely to have at least one remote operation (they are independend), that will take a lot of time.

Compare that to:

task_container tc;

for ( i = 0; i < 100.000; i++ ) { tc.add (job_server.create (jd[i])); // CREATE }

tc.run (); tc.wait ();

It is rather straigh forward to optimize the task container for bulk job submission, or bulk operations in general (we hope).

What I am not sure is, what would that look like in native java? Are there similar mechanisms?

Looking forward to your comments,

Andre.

...

Graeme

Quoting Andre Merzky :

...

Hi,

I just had a discussion with Thilo about the topic, as he and me obviously talked somewhat orthogonal to each other...

Well, now we have the same opinion, kind of, and I have barely any bruises... Anyway, I want to summarize our point here, as I probably was not really clear in my initial post.

Sorry if re-iteration of the topic bores you...

So, we have tasks, which represent async operations, with a couple of states attached, and the ability to call run(), wait() and cancel() on these. And we can collect them in containers, and wait() on many of these tasks conveniently.

And then we have jobs, which represent remote executables, with a couple of states attached, and the ability to call run (== create them), wait() and cancel(). And some more methods. And we can't collect them in containers right now, but would like to.

You see the similarities, right? Its even more obvious in code:

Tasks: -------------------------------------------- task_container tc; task t = file.copy saga::task (...); t.run ( ); t.wait (1.0);

tc.add (t); tc.wait ( ); --------------------------------------------

Jobs: -------------------------------------------- job_container jc; job j = job_server.submit (job_descr); j.wait (1.0);

jc.add (j); jc.wait ( ); --------------------------------------------

slightly changed: -------------------------------------------- job_container jc; ! job j = job_server.create (job_descr); + j.run ( ); j.wait (1.0);

jc.add (j); jc.wait ( ); --------------------------------------------

The similarities are obvious I think. Now, if job would IMPLEMENT the task interface (or inherit from task), we would unify both classes, and hence:

- simplify jobs (leave only those methods which are specific to jobs, like migrate, signal, ...

- allow to out jobs into task containers, efficiently handling large amounts of jobs and other tasks

- have the API and used paradigms more uniform.

Also, if later tasks get suspendable, as Gregor rightly suggested, we can move more methods to tasks, w/o breaking the paradigms.

In terms of state, following mappings would be appropriate:

job::Pending -> task::Pending job::Done -> task::Done job::Failed -> task::Failed job::??? -> task::Cancelled

job::Queued,Running,Pre/Poststaging,... -> task::Running

So, no adjustements to the statet models are needed AFAICS, apart from Cancelled (Does it make sense on jobs? Should job::stop be job::cancel? Should tasks::cancel be task::job?)

Hope that clearifies things. I think Gregor was on target with his remarks, and Hartmut signalled consent as well. And I think I convinced Thilo (Andre rubs his bruises).

Unless there is any opposition, I'll go ahead and document that in the strawman then, ok?

Cheers, Andre.

...

Date: Sat, 4 Feb 2006 22:29:41 +0100 From: Thilo Kielmann To: saga-rg@ggf.org Subject: Re: [saga-rg] tasks and jobs...

> Wouldn't it be useful to have jobs implementing the task > interface? Certainly, no. Jobs and Tasks are two different things, and they are this on

Quoting [Thilo Kielmann] (Feb 04 2006): purpose.

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However, Tasks always have been the mechanism for asynchronous operation, which is kind-of obsoleted by having asynchronous ops directly.

If you want to work on the "S" of SAGA: why not unify both Tasks and Jobs into a better "Job" notion, and do local asynchronous operations via async, local calls?

Thilo -- "So much time, so little to do..." -- Garfield

-- "So much time, so little to do..." -- Garfield