On Oct 28, 2008, at 3:16 PM, Jerry Krinock wrote:
On 2008 Oct, 28, at 9:09, Bill Bumgarner wrote:
That would not surprise me. An absolute microseconds overhead isn't a terribly useful measure without knowing the total # of microseconds. In general, measuring as a factor of speed -- 1.2x 20x 200x is more widely applicable (tends to be more consistent across different CPUs, for example).

Well, since you asked..... :))

Actually, I calculated this first but it seemed too ridiculous to publish.

                        Time to send message and
                       do 10,000 integer additions
                       ---------------------------
 Direct messaging         250 microseconds typical
 Message Forwarding    300000 microseconds typical
 "X" factor:             1200 X

Obviously this is because the "real work" was trivial. But I concocted my test that way purposely. The result of "20 microseconds per message on a 2006 Mac Mini" gives me a measure which I can use to ^predict^ performance in this and future applications ^before^ writing code.

Oooh... trivial tests!  I like those!   Can you share the code?

So... sure... message forwarding is slow. But does it matter in your application?

Early in the design process you need to make some guesses based on experience. Since I have an alternative to in this case, the decision is to use the alternative.

Roughly, the lesson is: Don't use message forwarding for "actual work". I was just wondering if anyone had ever found otherwise.

I'd rephrase that for archival purposes: Don't use message forwarding in tight loops or other repetitive use patterns. It doesn't make sense to have to figure out who is really going to do the work on each pass through a loop when figuring out who is so terribly expensive.

b.bum

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