Data transfer specifics for a queue

Documentation for parallel.pool.DataQueue and parallel.pool.PollableDataQueue says next to nothing about how data is transferred between the client and workers. I have two questions in particular about this functionality, although any related details would be much appreciated.

1. What can or can't be sent through the queue. During debugging I sent a daq session through the queue and although it appeared to transfer fine all the properties of the class were empty.
2. My understanding is that workers and the client are in separate processes (with separate memory management). When sending data through a queue what sort of locking takes place to transfer data between the processes? For example, does the worker somehow lock the client's memory management system while sending a message to the client, and similarly, have to wait for that lock if the client is doing memory allocation?

Answer 1

[Walter Roberson]

A message type interface is used, implemented through Java. The source elements are serialized, the serialized version transmitted, and the destination deserializes. The destination receives the information when convenient for it, so it cannot interfere with memory allocation.

Objects that are controlling a hardware resource cannot usually transfer the resource control through the queue.

[Jim Hokanson]

I expected as much for a hardware resource I just wasn't sure about other data types. Something like a graphics object might be able to transfer if the properties are copied, but not if they are all dynamically accessed relative to some handle. Function handles should transfer unless they have data bound to them, although the data could be copied as well ...

Since it uses Java does this impact the Java Heap Memory, both on the client and the worker side?

I'll take your word on the asynchronous message transfer. After I finish my current project I'll have to see if I can come up with a good test case that shows this to be true.

[Jim Hokanson]

Also, I'm really surprised it is done in Java since most of the data handling is done in C++. Do you have a source for this? I don't think it changes much, other than perhaps heap limit concerns, but I'm still curious.

[Walter Roberson]

You can read the source.

toolbox/distcomp/cluster/+parallel/+pool/DataQueue.m calls toolbox/distcomp/cluster/+parallel/+internal/+pool/AbstractDataQueue.m which does

              import com.mathworks.toolbox.distcomp.pmode.DataMessageDispatcher

and then does DataMesageDispatcher.createRemoteQueue and for that,

>> which com.mathworks.toolbox.distcomp.pmode.DataMessageDispatcher.createRemoteQueue

createRemoteQueue is a Java method  % static method or package function

[Jim Hokanson]

I always forget to try reading the source code! Thanks.