User's Manual

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Bome MIDI Translator: User's Manual 12 Behind the Scenes

Keystroke emulation takes a while to execute. So if you generate keystrokes

from a MIDI message but also do a lot of MIDI-to-MIDI translation, the

emulated keystroke would interrupt the MIDI translations until the

keystrokes are sent. For that reason, Outgoing Keystrokes are usually

enqueued for asynchronous execution.

Asynchronous execution has the advantage that it allows for much better

runtime performance. But on the other hand, it will be impossible to foresee

in which sequence Outgoing Actions are going to be executed: in the

example above, MIDI events arriving after the Outgoing Keystroke action

was enqueued are likely be processed before the Outgoing Keystroke(s) are

fully sent.

To make processing deterministic, the engine always guarantees that

outgoing actions of the same type are executed in the correct order.

12.3 Parallel Processing

MIDI Translator's engine is using advanced optimization techniques to

provide the best realtime processing performance even at heavy load and

when processing many different types of incoming events.

In particular, the engine is multi-threaded, using all processor cores on

modern multi-core processors. For example, the engine can process MIDI

events from different MIDI ports simultaneously. Some Outgoing Actions

can be executed simultaneously with other Outgoing Actions, some

Outgoing Actions are forced to be executed asynchronously in a separate

thread (see the example with Keystrokes in the previous chapter).

Multi-threading is nice for performance, but it may bring unexpected

behavior. In particular, be aware of parallel processing when using global

variables. Race conditions may occur where two events are processed

simultaneously and both change the same global variable. As a general rule,

you should use local variables whenever possible. Local variables' scope is

restricted to the particular incoming event, so it is not possible for a

concurrent event to cause problems with local variables.