Here is a quick & dirty benchmark to measure how fast we can stuff
data from the real world to a script using the LSL HTTP server. Data
may come from some sensor or human interaction device, maybe motion
capture, a Wii Remote, a Kinect ... and would control a simulation in
real-time.
The benchmark sends requests in the form seq=n, where n is an
incrementing sequence number. Any sequence gap on the receiver side
will indicate a lost message. There is an important assumption : we
are not interested in the reply and don't care reading it. This makes
a HUGE difference.
Code :
https://github.com/jeff-kelley/opensim-utils/tree/master/lsl_http-benchmark
Let's begin with the LSL script. It allocates a url then wait for a
request. GET and POST are supported. It checks the received sequence
number against the expected number and complains it they mismatch.
Finally, the script counts and display the number of requests it
receives every second.
On the client side, I chose Perl and the Net::HTTP class. No doubt
that could be written in Python, Ruby, C#, even PHP. The client opens
a HTTP connection in KeepAlive, then emit requests at a steady rate.
Inside the loop, the HTTP write is timed, and the wait to the next
request is computed.
The variable $reqSec controls the number of request per second.
Performing the test with different values gives an idea of the
overall performance.
Now for the unbelievable :
[09:56] Primitive: Requests/second : 207
[09:56] Primitive: Requests/second : 198
[09:56] Primitive: Requests/second : 220
[09:56] Primitive: Requests/second : 198
[09:56] Primitive: Requests/second : 214
[09:56] Primitive: Requests/second : 206
[09:56] Primitive: Requests/second : 207
[09:56] Primitive: Requests/second : 213
[09:56] Primitive: Requests/second : 207
Between two machine on a LAN, my figure is 200. Holy cow! This is
more than enough for a smooth simulation. As a bonus, you get a
high-speed, high-jitter event source.
LSL HTTP server slow ?
Not !
-- Jeff
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