Unroll the transaction loop

[nkrkv]

Rationale

Discussed on the forum. Quintessence is when we store the program graph in various global structures with tricky access functions we give a little chance for a C++ compiler to optimize.

If the desired sequence of evaluation would be presented as the code we should get a considerable efficiency boost both in terms of execution speed and RAM consumption.

Acceptance criteria

Here is a patch:

maps are from [0, 1] to [0, 1.1]. Compiled for Arduino UNO it gives:

Sketch uses 4244 bytes (13%) of program storage space. Maximum is 32256 bytes.
Global variables use 1030 bytes (50%) of dynamic memory, leaving 1018 bytes for local variables. Maximum is 2048 bytes.

After the loop unroll we should get less dynamic memory usage.

If we’d uncomment:

// Uncomment to turn on debug of the program
#define XOD_DEBUG

// Uncomment to trace the program runtime in the Serial Monitor
#define XOD_DEBUG_ENABLE_TRACE

We can see 34 transactions are done per second. That characteristic should be not worse after the optimization.