SirRoboGarage/common_libs/tests/test_bitbrain.nim

## Unit / sanity tests for the generic BitBrain (ADE + SBC) library.
##
## No Java, no battles, no I/O: everything here is deterministic and seeded.
## Run:
##   nim c -r --nimcache:/tmp/nc_j90 common_libs/tests/test_bitbrain.nim
##
## Covers:
##   * ADE scoring / thresholding against a hand-computed example,
##   * idempotent SBC learning (learn one sample 1000x -> identical memory),
##   * a planted rule learned near-perfectly,
##   * an online (incremental) learning curve that improves monotonically,
##   * a shuffled-label control that degrades to chance,
##   * correct, non-crashing behaviour on an unseen input,
##   * homeostatic threshold adaptation moves the firing rate toward target.

import std/[random, math, strutils]
import bitbrain/ade
import bitbrain/sbc
import bitbrain/bitbrain

var checks = 0
var failures = 0
proc check(name: string, ok: bool) =
  inc checks
  if ok: echo "PASS: ", name
  else: echo "FAIL: ", name; inc failures

proc randInput(rng: var Rand, n: int): seq[int] =
  result = newSeq[int](n)
  for i in 0 ..< n:
    result[i] = rng.rand(255)

# ── 1. ADE scoring / thresholding ────────────────────────────────────────────

proc testAdeScoring() =
  # One ADE with synapses: +index 2 (code +3), -index 0 (code -1).
  var ad = initAddressDecoder(1, 2, scale = 1, center = 127)
  ad.codes[0] = 3          # +1 * (2 + 1): position 2, excitatory
  ad.codes[1] = -1         # -1 * (0 + 1): position 0, inhibitory
  let input = @[10, 0, 200]  # raw = (200-127) - (10-127) = 73 + 117 = 190
  check "ADE hand-computed score is 190", ad.score(input, 0) == 190
  ad.thresholds[0] = 190
  check "ADE fires at score == threshold (>= comparison)", ad.fires(input, 0)
  ad.thresholds[0] = 191
  check "ADE does not fire one above score", not ad.fires(input, 0)

  # Two-ADE active list.
  var ad2 = initAddressDecoder(3, 1, scale = 1, center = 0)
  ad2.codes = @[1'i32, 2'i32, 3'i32]     # positions 0,1,2, all excitatory
  ad2.thresholds = @[5'i32, 5'i32, 5'i32]
  var active: seq[int32]
  ad2.activeList(@[10, 1, 10], active)
  check "active list picks exactly the firing ADEs", active == @[0'i32, 2'i32]

# ── 2. Idempotent SBC learning ───────────────────────────────────────────────

proc testIdempotentLearning() =
  var s = initSbc(64, 5)
  let row = @[1'i32, 3'i32, 7'i32]
  let col = @[2'i32, 4'i32]
  let firstAdded = s.learn(row, col, 2)
  check "first learn sets 3*2 = 6 bits", firstAdded == 6
  let snapshot = s.bits
  var allNoop = true
  for _ in 0 ..< 1000:
    if s.learn(row, col, 2) != 0: allNoop = false
  check "learning the same sample 1000x is a no-op", allNoop
  check "memory is bit-identical after 1000 repeats", s.bits == snapshot

  # Setting a *different* class bit is still new information.
  check "a different class sets new bits", s.learn(row, col, 3) == 6
  check "learned bit is readable", s.bitAt(1, 2, 3)
  check "unlearned bit is clear", not s.bitAt(1, 2, 4)

# ── 3. Synthetic planted-rule dataset ────────────────────────────────────────

const
  SynthInputWidth = 32
  SynthClasses = 4
  SynthBlock = 8          # positions owned by each class
  SynthHot = 4            # of the 8 block positions set per sample

proc synthSample(rng: var Rand, cls: int): seq[int] =
  ## Input is zero everywhere except `SynthHot` randomly chosen positions inside
  ## class `cls`'s block, set to 255. The class rules are disjoint in position
  ## space, so a rule of "which positions are hot" is perfectly learnable.
  result = newSeq[int](SynthInputWidth)
  var poss: seq[int]
  for p in 0 ..< SynthBlock:
    poss.add cls * SynthBlock + p
  rng.shuffle(poss)
  for k in 0 ..< SynthHot:
    result[poss[k]] = 255

proc synthAd(nAde: int, rng: var Rand): AddressDecoder =
  ## All-excitatory width-2 ADEs that fire iff *both* sampled positions are hot
  ## (score 2*255 == threshold 510).
  result = initRandomAddressDecoder(nAde, 2, SynthInputWidth, rng,
                                    scale = 1, center = 0, threshold = 510)
  for k in 0 ..< result.codes.len:
    result.codes[k] = abs(result.codes[k])

proc synthBrain(nAde: int, seed: int64): BitBrain =
  var rng = initRand(seed)
  var ades: seq[AddressDecoder]
  for _ in 0 ..< 3:               # a few ADs -> several cross SBCs
    ades.add synthAd(nAde, rng)
  initBitBrain(ades, crossPairs(ades.len), SynthClasses)

proc accuracy(bb: var BitBrain, xs: seq[seq[int]], ys: seq[int]): float =
  var right = 0
  for i in 0 ..< xs.len:
    if bb.infer(xs[i]).label == ys[i]:
      inc right
  result = float(right) / float(xs.len)

proc makeSynthSet(n: int, seed: int64): (seq[seq[int]], seq[int]) =
  var rng = initRand(seed)
  for i in 0 ..< n:
    let cls = i mod SynthClasses
    result[0].add synthSample(rng, cls)
    result[1].add cls

proc testPlantedRuleAndOnlineCurve() =
  var bb = synthBrain(256, seed = 20240924)
  var (testX, testY) = makeSynthSet(400, seed = 777)
  var (trainX, trainY) = makeSynthSet(600, seed = 111)

  # Incremental online learning: accuracy on held-out data must not go backwards
  # as samples arrive.
  var accs: seq[float]
  for i in 0 ..< trainX.len:
    bb.learn(trainX[i], trainY[i])
    if (i + 1) mod 50 == 0:
      accs.add accuracy(bb, testX, testY)

  for i in 1 ..< accs.len:
    check "online accuracy is monotone at checkpoint " & $((i + 1) * 50) &
          " (" & formatFloat(accs[i - 1], ffDecimal, 3) & " -> " &
          formatFloat(accs[i], ffDecimal, 3) & ")",
          accs[i] >= accs[i - 1]
  check "planted rule is learned near-perfectly (" &
        formatFloat(accs[^1], ffDecimal, 3) & " >= 0.95)",
        accs[^1] >= 0.95

# ── 4. Shuffled-label control ────────────────────────────────────────────────

proc testShuffledControl() =
  var bb = synthBrain(256, seed = 99)
  var (trainX, _) = makeSynthSet(3000, seed = 5)
  var (testX, testY) = makeSynthSet(400, seed = 6)
  var rng = initRand(4242)
  var shufY = newSeq[int](trainX.len)
  for i in 0 ..< trainX.len:
    shufY[i] = rng.rand(SynthClasses - 1)
  for i in 0 ..< trainX.len:
    bb.learn(trainX[i], shufY[i])
  let acc = accuracy(bb, testX, testY)
  check "shuffled-label control is near chance (" &
        formatFloat(acc, ffDecimal, 3) & " <= 0.45, chance = 0.25)",
        acc <= 0.45

# ── 5. Unseen input ──────────────────────────────────────────────────────────

proc testUnseenInput() =
  var bb = synthBrain(128, seed = 33)
  var (trainX, trainY) = makeSynthSet(400, seed = 44)
  for i in 0 ..< trainX.len:
    bb.learn(trainX[i], trainY[i])
  let blank = newSeq[int](SynthInputWidth)
  let r = bb.infer(blank)
  var total = 0
  for c in r.counts: total += c
  check "unseen all-zero input fires no ADE and has zero counts", total == 0
  check "unseen all-zero input still returns a valid class",
        r.label >= 0 and r.label < SynthClasses
  # A single hot position inside a class block should not crash and should
  # produce valid counts.
  var rng = initRand(1)
  var one = newSeq[int](SynthInputWidth)
  one[3 * SynthBlock + 2] = 255
  let r2 = bb.infer(one)
  check "unseen partial input returns a valid class/counts",
        r2.label >= 0 and r2.label < SynthClasses and r2.counts.len == SynthClasses

# ── 6. Homeostatic threshold adaptation ──────────────────────────────────────
proc testHomeostasis() =
  var rng = initRand(7)
  const N = 64
  const Interval = 400
  const Target = 0.10

  # All thresholds so high nothing fires -> controller must lower them.
  var hot = initRandomAddressDecoder(N, 4, 200, rng, scale = 1, center = 127,
                                     threshold = 100_000)
  var cold = initRandomAddressDecoder(N, 4, 200, rng, scale = 1, center = 127,
                                      threshold = -100_000)
  # A naturally-initialised AD (threshold 0) is used to test convergence.
  var mid = initRandomAddressDecoder(N, 4, 200, rng, scale = 1, center = 127,
                                     threshold = 0)
  for round in 0 ..< 300:
    for _ in 0 ..< Interval:
      let x = randInput(rng, 200)
      hot.accumulateFiring(x)
      cold.accumulateFiring(x)
      mid.accumulateFiring(x)
    hot.adaptThresholds(Interval, Target, step = 5)
    cold.adaptThresholds(Interval, Target, step = 5)
    mid.adaptThresholds(Interval, Target, step = 5)
  check "too-cold thresholds are driven down", hot.thresholds[0] < 100_000
  check "too-hot thresholds are driven up", cold.thresholds[0] > -100_000

  # Measure the converged firing rate of the naturally-initialised AD.
  var fired = 0
  for _ in 0 ..< 2000:
    fired += mid.fireCount(randInput(rng, 200))
  let rate = float(fired) / float(2000 * N)
  check "mid AD converges near the 10% target (got " &
        formatFloat(rate, ffDecimal, 3) & ")",
        rate > 0.05 and rate < 0.20

# ── 7. Memory accounting ─────────────────────────────────────────────────────

proc testMemoryAccounting() =
  # A gun-sized configuration: 4 ADs x 512 ADEs, widths {6,8,10,12}, 6 SBCs,
  # 8 classes. SBC tensors dominate: 6 * 512*512*8 bits = 1,572,864 bytes.
  var ades: seq[AddressDecoder]
  var rng = initRand(1)
  for w in [6, 8, 10, 12]:
    ades.add initRandomAddressDecoder(512, w, 256, rng)
  let bb = initBitBrain(ades, crossPairs(4), 8)
  check "gun-sized SBC memory = 1,572,864 bytes",
        bb.sbcMemoryBytes == 1_572_864
  check "gun-sized total model = SBC + AD codes/thresholds",
        bb.memoryBytes > bb.sbcMemoryBytes
  # The SBC tensor is exactly nAde*nAde*nClasses bits, rounded up to uint32.
  check "SBC tensor bit count is exact",
        bb.sbcMemoryBytes * 8 == 6 * 512 * 512 * 8

# ── driver ───────────────────────────────────────────────────────────────────

testAdeScoring()
testIdempotentLearning()
testPlantedRuleAndOnlineCurve()
testShuffledControl()
testUnseenInput()
testHomeostasis()
testMemoryAccounting()

echo "\n", checks, " checks, ", failures, " failure(s)"
if failures > 0:
  quit(1)
echo "All bitbrain sanity checks passed."