22.10.2013 18:17, David Lang:
I think this is going to be a source of ongoing confusion for users. I
don't see it being reasonable to create a global() function that can
do everything that anyone ever wants to do with global variables in
one shot. At least not until you start allowing a series of statements
to be passed to the funtion, effectively turning it into
atomic(
statement1
statement2
statement3
)
that combines these statements into one as far as the SIMD engine is
concerned.
Yes, that is what I've proposed earlier. I've also tried to emulate
sequential behaviour with call:
ruleset (name="xxx" queue.dequeuebatchsize="1") {
set $/zz = $/zz + 1;
set $!msgcnt = $/zz;
}
call xxx
But, unfortunately, this does not work. Perhaps queue parameters are
ignored in this case, because no queue is created. So each statement in
called ruleset is evaluated inline.
going off on a slight tangent, reading on SIMD (since I didn't
recognize the abbrevidation and had been misunderstanding your prior
explanation), this approach seems odd to take on modern CPUs. by
executing the same statement for each message in turn, and then going
on to the next staement, it seems like you are thrashing the CPU cache
as I would expect that the cache footprint for the data being
manipulated in a mesage to be overwelmingly larger than the cache
footprint of the statement being executed. It would seem that you
would be in much better shape to run all the commands against a single
message, keeping that message in the cache as much as possible, and
then going on to the next message. Not to mention the increased memory
use if processing each message sets a bunch of variables, because the
current approach requires that all the variables for all the messages
be generated at the same time, rather than creating all the variables
for one message, then being able to throw them all away when you go to
work on the next message.
I presume, that message data is substantially smaller than code size.
Say, average message is 200 bytes and code to handle it is several
hundreds of kilobytes. But I also wonder what is the reason of having
SIMD engine. Perhaps it is possibility to submit all messages at once
for a single action?
--
Pavel Levshin
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