Difference: DocsSectionsExampleSpellerPart3 (2 vs. 3)

Revision 305 Jan 2012 - Main.MarjoleinVanDerWaal

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Example 2: Visual speller

Part 3

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  In the previous parts of this visual speller example, all actions were executed by the BrainStream Matlab session. In this section, we will describe how to enable parallel processing. All actions related to stimulus presentation will be handled by a client.
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First, we need to indicate that we want to use parallel processing and define the client. This can be done in the block file speller_common.blk:
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Below, the new flowcharts of the experiment are shown. Actions indicated in orange are executed at the BrainStream Matlab session, whereas actions indicated in blue are executed at the client.

flowchart_main_3.png

Figure 1: Main flowchart. In the stimulus presentation plug-in, actions are defined for the BrainStream Matlab session as well as the client (see Figure 2).

At the start of the experiment, the speller is intialized on the client. The client then sends a marker to BrainStream to trigger the initTrain function. The advantage of this construction is that you are always sure that the stimulus client is correctly initialized before the actual experiment starts.

flowchart_plugin_2.png

Figure 2: Plug-in flowchart

In the plug-in flowchart you can see why it is advantageous to use parallel processing: if the action of updating the codebook (at the BrainStream session) is delayed or takes more than 0.07 seconds, the duration of the stimulus (at the client) is not affected.

In order to build this experiment, we first need to indicate that we want to use parallel processing and define the client. This can be done in the block file speller_common.blk:

 
[RunMode]
Parallel=1;
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  stim1.png
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Figure 1: Actions sheet of the speller_train table
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Figure 3: Actions sheet of the speller_train table
  stim2_2.png
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Figure 2: Actions sheet of the speller_common table
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Figure 4: Actions sheet of the speller_common table

Evaluation


  <- Go back to Part 2 - Continue with Part 4 ->

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