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Alessandro Crugnola on January 5, 2009 in actionscript , python

Loading images via http vs bytearray

Load images via http or using bytearray? which the best way?
It was long time since I wanted to perform this kind of test, but for different reasons I never had the time to do that. 
Some days ago fnally I've found the time thanks to a project I'm involved into.

The problem.
A local webserver running flash remoting via pyamf and a flash standalone application which need to load tons of images locally.
I've noticed that sending from amf the list of images path to be loaded required too much time (for me), even if they're loaded locally.

Because of this I decided to try a first benchmark loading a single image using the standard way: send the link from amf and then load it using the classic actionscript Loader.
The second test was to send directly from amf the image stream using a ByteArray and then loading the image in flash using the Loader.loadBytes method.
In this way I've noticed that the second task requires less time than the first one (more or less 40% less).

Unfortunately our application needs to load something like 50/100 images at the same time.
For this reason I did a new test loading 22 images of 500Kb each (10Mb total). For a better result I decided to use both pyamf and blazeds, to be sure there's no problems in the language used. Moreover I used charles to register the benchmark of these tasks.

The results were unexpected!

First test: passing form amf the list of url images and loading using the standard flash Loader to load all of them simultaneously.
The time elapsed from the flash method call to the results was about 40 milliseconds. Then from the remote method result to the completion of all Loader about 1400 milliseconds.

Second test: passing from amf an arraycollection of bytearrays containing all the images stream to be loaded directly in flash.
The time elapsed form the flash method call to its result: about 2900 milliseconds. Time elapsed from the result to the all Loaders completion: about 900 milliseconds.

This results were unexpected for me, expecially because both with blazeds and pyamf sending 10Mb of bytearrays tooks something like 3 seconds! At a first impression I thought the problem was the time for java and python to create the amf stream data, but after a deeper test I discovered that they took more or less 30ms to generate the amf stream and the real bottleneck was the http transfer of this stream data.

I'm attaching here the screenshots of the charles sessions both using blazeds:


and pyamf:


Here you can find also the complete benchmark result using flash trace within the swf:


Method Elapsed-Time
call.test1 0
result.test1 40
complete.test1 1453

call.test2 0
result.test2 2919
complete.test2 921


call.test1 0
result.test1 32
complete.test1 953

call.test2 0
result.test2 2805
complete.test2 908

Here you can see the source code used for these tests:

and the Flex project:

In conclusion. While sending 10Mb of data ( for example bytearray ) requires more or less 2.5 seconds using flash remoting as single requests ( because the transfer rate of the webserver it's about 4Mb/sec ), loading simultaneusly 20 images from the webserver, using http, tooks 1 second. This is because the webserver for each requests opens a different thread to dispatch the request and in this way the total time to perform this task is less than the first method.


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Tags: amf , benchmark , blazeds , bytearray , charles , pyamf 


Hi Alessandro, thanks for doing those benchmarks. I'm probably missing something but it looks like the benchmarks don't add up correctly. I mean, for the blazeds test we have 40 + 1453 (=1493) and 2919 + 921 = 3840, which is all good. But for PyAMF it's 32 + 953 (=985, and not 1049) and 2805 + 908 (=3713, and not 4763). So yeah, the test result total shows PyAMF is faster compared to BlazeDS but since the calculation seems broken I'm not sure what to think of these results.. :)
Very surprising results, indeed !

Why not merging your images into a single ZIP file, with no compression, and using FZip library (or similar) to load it ?
I have been working on a project with tons of pictures to load, and each time we added a picture we just had to rebuild the zip file with a simple command line or a dedicated tool we built quickly (our tool was made with TCL/Tk, coded in a couple a minutes, then converted to exe format ; but almost any language can fit) ; then it was very handy to manage our huge images collection in AS3, thanks to FZip :)


Good post...This does in fact show that loading bytes is faster using the Flash Player than what the browser provides for data transfer.
Thanks for running these tests Alessandro, it's a shame you weren't able to find any performance increases tho.

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