Optimize Connections data structure

[chetan51]

Play with the following:

• Use 1 byte for permanence, instead of 32 bytes
• Fix connected permanence to 0.5, and only check most significant bit when checking if connected

Profile and optimize.

edit: Part of #7

[breznak]

@chetan51 or even 1bit - std::bitset or std::vector<bool> with trickery. https://stackoverflow.com/questions/3806469/bit-array-in-c

On a second thought, could this collide with SSE which need some sort of alignment (to 16B? )?

Also, Connections is used only for temporal memory, or also shared for SP/TP? (or what would be their equivalent data structures?)

[rcrowder]

I like this idea. 16 bit fixed point for Permanence sounds like it will be enough to cover range of permanence values. And top bit checking falls out of the FP math 😄 Looks like a quick thing to try in the TM/Connections class(es).

[rhyolight]

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