Adds an smCounted storage mode alongside the default smBitset. Each
(i,j,class) cell becomes a saturating uint8 counter; learn increments it and
a global fractional decay (c -= c shr decayShift every decayEvery learns)
makes forgetting possible. infer sums raw counters; new inferProb sums the
per-cell posterior P(class|cell) (scale-free, recommended readout).
Bitset path is the default and byte-for-byte unchanged: test_bitbrain 56/56
(was 32), and test_bitbrain_mnist reproduces 97.210% corrected / 96.540%
bug-compatible exactly.
Counted mode configurable at runtime (TR_BITBRAIN_MODE / TR_BITBRAIN_DECAY_*)
and compile time (-d:bitbrainDecay*). Measured: forgetting (86.2% vs 48.9% on
a permuted-label stream), probabilities (rare-class balanced 0.998 vs 0.500),
and the stationary cost (counted hurts MNIST; see docs/bitbrain_counted_sbc.md).
Harness: common_libs/tests/measure_counted_sbc.nim
Implement the BitBrain (Address Decoder Element + Sparse Binary Coincidence)
classifier as a generic, deterministic Nim library under common_libs/bitbrain/,
written from the published algorithm (Front. Neuroinform. 17:1125844), not from
the GPL-3.0 reference C.
- ade.nim: signed thresholded random projection (scale 64 / centre 127 defaults
reproduce the reference), multi-width ADs, optional deterministic homeostatic
threshold adaptation. Hebbian longevity and Metropolis-Hastings sampling are
described but not implemented.
- sbc.nim: packed class-bit coincidence memory; idempotent learn, counting
inference.
- bitbrain.nim: container over several ADs and SBCs, online learn/infer, argmax
readout, memory accounting.
- tests: 32 unit checks (idempotence, planted rule + monotone online curve,
shuffled-label chance control, unseen input, homeostasis, memory).
- tests/test_bitbrain_mnist.nim: loads the reference pretrained ADs/thresholds
and MNIST from /tmp, reproduces the reference exactly - 97.210% corrected and
96.540% bug-compatible - confirming the port.
No gun/wiring integration yet; inputs and outputs to be agreed separately.
SirStone