Hi all,
I'm updating some parallel Julia code to support 0.5. I see that
the RemoteRef type is no longer supported. It seems I need to replace these
with a mix of Future and RemoteChannel. The use of Future is clear enough
but I'm unclear on the best way to use RemoteChannels, in the following
context: Suppose I want to initialize an instance of some complicated
composite type MyBigType on a remote worker. Later on I want to modify that
instance, use it for some computations and continue storing it for another
later use. On julia 0.4 I can do
R = RemoteRef{Channel{Any}}
R = remote_call(pid,constructMyBigType,arguments)
a can then be a reusable storage location, i.e. one can do things like
Rval = take!(R)
Rval = computeSomething(Rval) #Modifies some fields of aval, leaves
others untouched
put!(R,Rval)
That doesn't work on 0.5. since the RemoteRef type is gone. So far, my
solution is to first send all arguments needed by the constructor function
to the remote worker, then define a helper function that calls the
constructor then puts it in a channel. The helper function is
@everywhere begin
function remoteTypeConstructor(arguments)
obj = constructMyBigType(arguments)
chan = Channel{MyBigType}(1)
put!(chan,obj)
end
end
Then from the master Julia process I use the following two lines of code to
define the remote channel, which is a reference to the MyBigType instance
stored on worker pid.
sendToWorker(arguments,pid)
R = RemoteChannel(()->remoteTypeConstructor(arguments), pid)
Once I've defined R I can work with it using take!() and put!() just like
in 0.4. The type constructor function here could possibly be
computationally intensive and the resulting object could occupy a lot of
memory so I'd like to have the constructor function run on the remote
worker. The approach I've just defined seems to work but it's pretty
awkward and could become tricky/a pain to manage if I have to write one of
these helper functions for every new type of data I want to compute and
store using a RemoteChannel. I'm wondering if there's a better way to do
what I'm trying to do?
Thanks very much, Patrick
