Subject:
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Re: NQC versus Lego RCX Code Speed
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Newsgroups:
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lugnet.robotics
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Date:
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Fri, 6 Oct 2000 20:12:08 GMT
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Viewed:
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633 times
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Wilcox, Doug <Doug.Wilcox@iMcKesson.com> wrote:
> I noticed this when I had a fairly simple program written in RCX Code that
> was checking two separate bumpers and backing and turning depending on which
> one was pressed. (The only other routine in the program was to emit a beep
> every 5 seconds) The second bumper would only "trigger" after a 1-2 second
> delay. I thought I had a bad RCX or bad sensor, but I tried the same program
> on my second RCX with different sensors, and the same thing happened! This
> delay behavior might only be a problem using certain combinations of Sensor
> Watchers, but it did get me thinking about what's going on under the hood.
With regards to your comment about sensor watchers, yes they are slow. If
I remember correctly, they are implemented by a task that loops forever
polling the sensors and starting other tasks whenever an event of the
proper type occurs. Tasks are executed in a tightly interleaved fashion
(one instruction at a time from each active task), which I imagine is not
particularly efficient in some cases. For example, when a sensor watcher
is triggered, I believe the poll task is still running, increasing response
time by at least 2x.
With NQC, you have control over how sensors are polled and how the
responses execute. If you stick to a single task, you normally stop
polling while you are responding to an event, reducing response time.
Does this explain what you observe?
-Kekoa
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Message has 1 Reply:
 | | Re: NQC versus Lego RCX Code Speed
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| Yes, this explains my observations perfectly! I will probably set up some more experiments--attempting to exactly duplicate the function of my oddly-behaving RCX Code (my currently-running NQC program is very close already), and try to get some real (...) (24 years ago, 7-Oct-00, to lugnet.robotics)
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Message is in Reply To:
| | RE: NQC versus Lego RCX Code Speed
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| Thanks very much, everyone, for the detailed answers. I suspect that, due to the huge performance gain I seem to get using NQC (in one observable area: touch sensor response time using two touch sensors on two separate ports), that the RCX Code (...) (24 years ago, 6-Oct-00, to lugnet.robotics)
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