From 0ee5c21ef5b8b234fdff69ae4c6917abf463d4f2 Mon Sep 17 00:00:00 2001
From: Davide Cappellini <signorsasso@gmail.com>
Date: Mon, 14 Sep 2026 22:08:22 +0200
Subject: [PATCH] fix(SNNBot): store SNN state in aim snapshots for correct
 retroactive learning
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The retroactive error signal matures many ticks after the snapshot was taken,
but superSpikeUpdate was using bot.lastSpikes/lastVSnap which had been
overwritten by subsequent DECIDE cycles. Learning was applied against wrong
neural activity — effectively random weight perturbations.

Fix: AimSnapshot now captures spikes, vSnap, and preTrace at DECIDE time.
superSpikeUpdate receives these saved values at maturation instead of the
stale current state.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
---
 SNNBot_garage/src/SNNBot.nim | 34 ++++++++++++++++++++++++++--------
 1 file changed, 26 insertions(+), 8 deletions(-)

diff --git a/SNNBot_garage/src/SNNBot.nim b/SNNBot_garage/src/SNNBot.nim
index 74ca77f..085e58c 100644
--- a/SNNBot_garage/src/SNNBot.nim
+++ b/SNNBot_garage/src/SNNBot.nim
@@ -142,10 +142,11 @@ proc forward(snn: var SNN, inputs: array[N_IN, float],
 proc superSpikeUpdate(snn: var SNN,
                       spikes: array[N_HID, float],
                       vSnap: array[N_HID, float],
+                      preTrace: array[N_IN, float],
                       targetAngle: float) =
   ## SuperSpike three-factor weight update.
   ## Δw = η × pre_trace × σ'(U) × error
-  ## spikes: accumulated counts over N_INFER ticks (0..N_INFER); normalized to rates.
+  ## spikes/vSnap/preTrace: captured at DECIDE time for this inference window.
   ## Output error: target_rate − actual_rate (rate-coded target).
   ## Hidden error: projected via fixed random feedback weights B.
 
@@ -183,7 +184,7 @@ proc superSpikeUpdate(snn: var SNN,
     let sg     = surrogateDerivative(vSnap[h])
     let errHid = snn.bFb[h * 2 + 0] * errSin + snn.bFb[h * 2 + 1] * errCos
     for i in 0 ..< N_IN:
-      snn.wih[i * N_HID + h] += ETA * snn.preTrace[i] * sg * errHid
+      snn.wih[i * N_HID + h] += ETA * preTrace[i] * sg * errHid
       snn.wih[i * N_HID + h] = snn.wih[i * N_HID + h].clamp(-W_CLAMP, W_CLAMP)
 
 # ── Bot state machine ─────────────────────────────────────────────────────────
@@ -198,6 +199,9 @@ type
     botX:       float   # bot position at snapshot time
     botY:       float
     gunHeading: float   # absolute gun heading at snapshot time
+    spikes:     array[N_HID, float]  # accumulated spike counts from this inference window
+    vSnap:      array[N_HID, float]  # hidden voltages from this inference window
+    preTrace:   array[N_IN, float]   # pre-synaptic traces from this inference window
 
   SNNBot = ref object of Bot
     snn:          SNN
@@ -427,14 +431,18 @@ method run*(bot: SNNBot) =
       bot.snn.lastSinOut = totalSin; bot.snn.lastCosOut = totalCos
       bot.snn.lastSnnAngle = arctan2(totalSin, totalCos) * 180.0 / PI
       bot.targetAngle = gunDir + bot.snn.lastSnnAngle
-      # Record aim snapshot for retroactive error signal
+      # Record aim snapshot for retroactive error signal; capture SNN state now
+      # before subsequent DECIDE cycles overwrite bot.lastSpikes / bot.lastVSnap.
       bot.snapshots.add(AimSnapshot(
         aimAngle:   bot.snn.lastSnnAngle,
         distance:   bot.enemyDist,
         tick:       bot.tick,
         botX:       myX,
         botY:       myY,
-        gunHeading: gunDir))
+        gunHeading: gunDir,
+        spikes:     bot.lastSpikes,
+        vSnap:      bot.lastVSnap,
+        preTrace:   bot.snn.preTrace))
       # Log total spike count across inference window
       var spikeCount = 0
       var maxV = 0.0
@@ -458,6 +466,10 @@ method run*(bot: SNNBot) =
       var retroTarget = bot.lastRelBearing  # fallback (unused if no matured snapshot)
       var hasMatured = false
       var keepIdx = 0  # first non-matured snapshot to keep
+      # matureSnap holds the last matured snapshot's SNN state for the weight update.
+      var matureSpikes:   array[N_HID, float]
+      var matureVSnap:    array[N_HID, float]
+      var maturePreTrace: array[N_IN, float]
       for i in 0 ..< bot.snapshots.len:
         let snap = bot.snapshots[i]
         let travelTicks = int(ceil(snap.distance / BULLET_SPEED))
@@ -474,16 +486,22 @@ method run*(bot: SNNBot) =
             let ex = bot.posBuf[foundSlot].x
             let ey = bot.posBuf[foundSlot].y
             let absBearing = directionTo(snap.botX, snap.botY, ex, ey)
-            retroTarget = normalizeRelativeAngle(absBearing - snap.gunHeading)
-            hasMatured = true
+            retroTarget    = normalizeRelativeAngle(absBearing - snap.gunHeading)
+            matureSpikes   = snap.spikes
+            matureVSnap    = snap.vSnap
+            maturePreTrace = snap.preTrace
+            hasMatured     = true
           keepIdx = i + 1  # discard matured snapshots up to and including this one
         else:
           break  # snapshots are in order; stop at first non-matured
-      # Discard matured snapshots
+      # Discard matured snapshots; immature ones are preserved automatically (keepIdx stays 0
+      # or points past the last matured entry; the rest of bot.snapshots is kept intact).
       if keepIdx > 0:
         bot.snapshots = bot.snapshots[keepIdx .. ^1]
       if hasMatured:
-        bot.snn.superSpikeUpdate(bot.lastSpikes, bot.lastVSnap, retroTarget)
+        # Use SNN state captured at DECIDE time — not the stale bot.lastSpikes/lastVSnap
+        # which have been overwritten by subsequent DECIDE cycles.
+        bot.snn.superSpikeUpdate(matureSpikes, matureVSnap, maturePreTrace, retroTarget)
       # else: skip weight update — no matured snapshot yet (early game)
       # Compute verbose logging metrics
       var spikeCount = 0