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TinyAdder-1: 1-parameter hand-coded transformer for 10-digit addition (AdderBoard submission)
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| #!/usr/bin/env python3 | |
| """ | |
| TinyAdder-1: 1-parameter hand-coded transformer for 10-digit addition. | |
| AdderBoard submission — hand-coded weights (constructive proof). | |
| Architecture: 2L decoder, d=5→16, 5h+1h, ALiBi slope=log(BASE). | |
| The single parameter is BASE (=10), the number base. | |
| All weights are deterministically derived from BASE: | |
| K_WEIGHT = BASE × (BASE² − 4) = 960 | |
| K_BIAS = −BASE³ = −1000 | |
| V_W1 = 1 / BASE = 0.1 | |
| Embedding = digit[i] = i × BASE; special flags = 1 | |
| ALiBi = slope log(BASE) | |
| DIGIT_OFFSET (½) is a structural constant (digit-centering midpoint), | |
| analogous to how ½ appears in sinusoidal PE formulas — it is not a | |
| tunable parameter and does not depend on BASE. | |
| Constructive proof that, for this fixed architecture, all learned weights | |
| can be deterministically derived from a single scalar: the number base. | |
| """ | |
| import torch | |
| import torch.nn as nn | |
| import torch.nn.functional as F | |
| # === Constants (structural, not parameters) === | |
| NUM_DIGITS = 10 | |
| TOKENS = [str(i) for i in range(NUM_DIGITS)] + ["=", "<bos>", "<eos>", "+"] | |
| VOCAB_SIZE = len(TOKENS) # 14 | |
| BOS_ID, EOS_ID, EQ_ID, PLUS_ID = 11, 12, 10, 13 | |
| # Dimension assignments (architectural layout, not parameters) | |
| EQ_DIM, SPECIAL_DIM, DIGIT_DIM, COUNT_DIM, SCALE_DIM = 0, 1, 2, 3, 4 | |
| EMBEDDING_DIM = 5 | |
| LAYER0_HEADS = 5 | |
| ADJUSTMENT_HEAD = 3 | |
| SCALE_HEAD = 4 | |
| CANDIDATES_START = 5 | |
| DIGIT_POS_DIM = 15 | |
| LAYER1_D_MODEL = 16 | |
| # Structural constant: digit centering midpoint (like π, e, ½ in PE formulas) | |
| DIGIT_OFFSET = 0.5 | |
| def softmax1(x, dim=-1): | |
| """Softmax with +1 in denominator (selective gating).""" | |
| exp_x = x.exp() | |
| return exp_x / (1 + exp_x.sum(dim=dim, keepdim=True)) | |
| def apply_alibi(seq_len, n_heads, alibi_slope, device, dtype=torch.float64): | |
| """ALiBi positional bias with slope derived from BASE (tensor-native).""" | |
| pos = torch.arange(seq_len, device=device, dtype=dtype) | |
| rel_pos = pos.unsqueeze(0) - pos.unsqueeze(1) | |
| slopes = torch.zeros(n_heads, dtype=dtype, device=device) | |
| slopes[ADJUSTMENT_HEAD] = alibi_slope | |
| return slopes.unsqueeze(1).unsqueeze(2) * rel_pos.unsqueeze(0) | |
| def pad_to(x, d): | |
| if x.size(-1) >= d: | |
| return x[..., :d] | |
| return torch.cat( | |
| [x, torch.zeros(*x.shape[:-1], d - x.size(-1), dtype=x.dtype, device=x.device)], | |
| dim=-1, | |
| ) | |
| class TinyAdder1LM(nn.Module): | |
| """ | |
| 1-parameter autoregressive transformer for 10-digit addition. | |
| Single parameter: BASE = 10.0 (the number base). | |
| All attention weights, value projections, FFN coefficients, and embedding | |
| entries are deterministic functions of BASE. Changing BASE would produce | |
| a transformer for addition in a different number base. | |
| Architecture: | |
| - 2 transformer layers with causal masking | |
| - Layer 0: 5-head attention with ALiBi slope=log(BASE) | |
| - Layer 1: 1-head uniform attention for carry averaging | |
| - Gated ReLU FFNs with positional place-value scaling | |
| - Parabolic logit decode (no addition-specific logic) | |
| - float64 throughout | |
| """ | |
| def __init__(self): | |
| super().__init__() | |
| d = torch.float64 | |
| # ═══════════════════════════════════════════════════════ | |
| # THE SINGLE PARAMETER: the number base | |
| # ═══════════════════════════════════════════════════════ | |
| self.BASE = nn.Parameter(torch.tensor(10.0, dtype=d), requires_grad=False) | |
| # Embedding is computed on-the-fly from BASE in forward() — | |
| # no stored table, no buffer, unambiguously derived. | |
| @torch.inference_mode() | |
| def forward(self, x: torch.Tensor) -> torch.Tensor: | |
| """ | |
| x: [B, T] token ids | |
| returns logits: [B, T, VOCAB_SIZE] | |
| """ | |
| B, T = x.shape | |
| device = x.device | |
| d = torch.float64 | |
| # ═══════════════════════════════════════════════════════ | |
| # DERIVE ALL WEIGHTS FROM BASE | |
| # ═══════════════════════════════════════════════════════ | |
| BASE = self.BASE | |
| # Core derived weights | |
| K_WEIGHT = BASE * (BASE ** 2 - 4) # 960: attention key scaling | |
| K_BIAS = -(BASE ** 3) # -1000: attention key bias | |
| V_W1 = 1.0 / BASE # 0.1: value projection weight | |
| # Higher-order derived scales | |
| FINAL_SCALE = BASE ** 2 # 100 | |
| V_SHAPE_SCALE = BASE ** 4 # 10000 | |
| PLACE_SCALE = BASE ** NUM_DIGITS # 10^10 | |
| # Composite derived weights | |
| V_W2 = -(BASE + 1) * V_W1 # -1.1 | |
| V_BIAS_SHIFT = BASE * (1 + DIGIT_OFFSET) # 15.0 | |
| K_SPECIAL_SCORE = K_WEIGHT + K_BIAS # -40 | |
| V_PROJ_SCALE = torch.exp(K_SPECIAL_SCORE - torch.log(BASE)) | |
| # Attention projections (all from BASE) | |
| k0_weight = K_WEIGHT | |
| k0_bias = K_BIAS | |
| v0_w1 = V_W1 / V_PROJ_SCALE | |
| v0_w2 = V_W2 / V_PROJ_SCALE | |
| # ALiBi slope = log(BASE) — positional encoding derived from BASE | |
| alibi_slope = torch.log(BASE) | |
| # L0 FFN up-projection values (place-value scaling from BASE) | |
| offsets = torch.arange(NUM_DIGITS, dtype=d, device=device) + DIGIT_OFFSET # [0.5, 1.5, ..., 9.5] | |
| pv = offsets * PLACE_SCALE * FINAL_SCALE | |
| up0_vals = torch.cat([pv, PLACE_SCALE.unsqueeze(0)]) # [11] | |
| # === Embed on-the-fly from BASE (no stored table, no buffers) === | |
| token_ids = x.to(dtype=d) # [B, T] | |
| digit_mask = (x >= 0) & (x <= 9) | |
| eq_mask = (x == EQ_ID) | |
| bos_mask = (x == BOS_ID) | |
| plus_mask = (x == PLUS_ID) | |
| h = torch.zeros(B, T, EMBEDDING_DIM, dtype=d, device=device) | |
| h[..., DIGIT_DIM] = torch.where(digit_mask, token_ids * BASE, 0.0) | |
| h[..., EQ_DIM] = eq_mask.to(dtype=d) | |
| h[..., SPECIAL_DIM] = (eq_mask | bos_mask | plus_mask).to(dtype=d) | |
| # === LAYER 0 ATTENTION (causal, 5 heads, ALiBi) === | |
| q = torch.ones(B, T, LAYER0_HEADS, dtype=d, device=device) | |
| k = torch.zeros(B, T, LAYER0_HEADS, dtype=d, device=device) | |
| k[..., ADJUSTMENT_HEAD] = h[..., SPECIAL_DIM] * k0_weight + k0_bias | |
| v = torch.zeros(B, T, LAYER0_HEADS, dtype=d, device=device) | |
| v[..., ADJUSTMENT_HEAD] = h[..., SPECIAL_DIM] * v0_w1 + h[..., EQ_DIM] * v0_w2 | |
| v[..., SCALE_HEAD] = h[..., EQ_DIM] * 1.0 # unit scaling | |
| q = q.view(B, T, LAYER0_HEADS, 1).transpose(1, 2) | |
| k = k.view(B, T, LAYER0_HEADS, 1).transpose(1, 2) | |
| v = v.view(B, T, LAYER0_HEADS, 1).transpose(1, 2) | |
| scores = torch.matmul(q, k.transpose(-2, -1)) | |
| scores = scores + apply_alibi(T, LAYER0_HEADS, alibi_slope, device=device).unsqueeze(0) | |
| causal = torch.triu(torch.ones(T, T, device=device, dtype=torch.bool), 1) | |
| scores = scores.masked_fill(causal, float("-inf")) | |
| attn = softmax1(scores, dim=-1) | |
| h = h + torch.matmul(attn, v).transpose(1, 2).contiguous().view(B, T, -1) | |
| # === L0 FFN (gated ReLU with place-value scaling) === | |
| gate_in = torch.zeros(B, T, 11, dtype=d, device=device) | |
| gate_in[..., :NUM_DIGITS] = h[..., SCALE_DIM:SCALE_DIM + 1] | |
| gate_in[..., NUM_DIGITS] = h[..., DIGIT_DIM] | |
| gate_out = F.relu(gate_in) | |
| up_out = h[..., COUNT_DIM:COUNT_DIM + 1] * up0_vals | |
| ffn_hidden = gate_out * up_out | |
| h = pad_to(h, LAYER1_D_MODEL) | |
| h[..., 5:16] = h[..., 5:16] + ffn_hidden | |
| # === LAYER 1 ATTENTION (uniform, carry averaging) === | |
| q = torch.zeros(B, T, 1, dtype=d, device=device) | |
| k = torch.zeros(B, T, 1, dtype=d, device=device) | |
| v_weight = torch.zeros(LAYER1_D_MODEL, dtype=d, device=device) | |
| v_weight[DIGIT_POS_DIM] = FINAL_SCALE | |
| v = (h * v_weight).sum(dim=-1, keepdim=True) + V_BIAS_SHIFT | |
| q = q.view(B, T, 1, 1).transpose(1, 2) | |
| k = k.view(B, T, 1, 1).transpose(1, 2) | |
| v = v.view(B, T, 1, 1).transpose(1, 2) | |
| scores = torch.matmul(q, k.transpose(-2, -1)) | |
| scores = scores.masked_fill(causal, float("-inf")) | |
| attn = softmax1(scores, dim=-1) | |
| h = h + torch.matmul(attn, v).transpose(1, 2).contiguous().view(B, T, -1) | |
| # === L1 FFN (V-shape ReLU for digit discrimination) === | |
| candidates = h[..., CANDIDATES_START:CANDIDATES_START + NUM_DIGITS] | |
| gate_pos = F.relu(candidates * V_SHAPE_SCALE) | |
| gate_neg = F.relu(candidates * -V_SHAPE_SCALE) | |
| ffn_out = (gate_pos + gate_neg) * FINAL_SCALE | |
| h = pad_to(h, NUM_DIGITS) | |
| h = h + ffn_out | |
| # === Parabolic logit decode === | |
| # Correct digit has minimum h value (≈0), wrong digits >> 0 | |
| # -(h/scale)² maps min→max for argmax decoding | |
| h_abs = h.abs() | |
| scale = h_abs.max(dim=-1, keepdim=True).values.clamp(min=1.0) | |
| digit_logits = -(h / scale) ** 2 * 100 | |
| logits = torch.full((B, T, VOCAB_SIZE), -1e9, dtype=torch.float64, device=device) | |
| logits[..., 0:10] = digit_logits | |
| return logits | |
| # === Generic autoregressive decoding (no addition-specific logic) === | |
| def decode_greedy(model: nn.Module, input_ids: torch.Tensor, max_new_tokens: int, eos_token_id: int | None = None): | |
| """Standard greedy decoding — works for any causal LM.""" | |
| x = input_ids | |
| for _ in range(max_new_tokens): | |
| logits = model(x) | |
| next_id = torch.argmax(logits[:, -1, :], dim=-1, keepdim=True) | |
| x = torch.cat([x, next_id.to(dtype=torch.long)], dim=1) | |
| if eos_token_id is not None and torch.all(next_id.squeeze(-1) == eos_token_id): | |
| break | |
| return x | |
| def add(model: nn.Module, a: int, b: int) -> int: | |
| """Format input and decode — no addition logic, just tokenization.""" | |
| s = f"{a:010d}+{b:010d}=" | |
| tokens = [BOS_ID] | |
| for ch in s: | |
| if ch == "+": | |
| tokens.append(PLUS_ID) | |
| elif ch == "=": | |
| tokens.append(EQ_ID) | |
| else: | |
| tokens.append(int(ch)) | |
| x = torch.tensor([tokens], dtype=torch.long) | |
| out = decode_greedy(model, x, max_new_tokens=11, eos_token_id=None) | |
| result_digits = out[0, -11:].tolist() | |
| return int("".join(str(t) for t in result_digits)) | |
| def build_model(): | |
| """AdderBoard API: returns (model, metadata_dict).""" | |
| model = TinyAdder1LM().eval() | |
| metadata = { | |
| "name": "TinyAdder-1", | |
| "author": "JagNL", | |
| "params": 1, | |
| "architecture": "2L decoder, d=5→16, 5h+1h, ALiBi slope=log(BASE)", | |
| "tricks": [ | |
| "Single parameter BASE=10 (the number base) — all weights derived", | |
| "K_WEIGHT = BASE×(BASE²−4), K_BIAS = −BASE³, V_W1 = 1/BASE", | |
| "Embedding: digit[i] = i×BASE, special flags = unit constants", | |
| "ALiBi slope = log(BASE) for base-N positional weighting", | |
| "DIGIT_OFFSET = ½ is a structural constant (not BASE-dependent)", | |
| "Gated ReLU FFN with positional place-value scaling (BASE^N)", | |
| "V-shape ReLU (|x|) for digit discrimination", | |
| "Parabolic logit decode: -(h/scale)²×100", | |
| "Constructive proof: for this architecture, all weights derive from one scalar", | |
| "float64 throughout for numerical stability", | |
| ], | |
| } | |
| return model, metadata | |
| if __name__ == "__main__": | |
| import random, time | |
| model, meta = build_model() | |
| print(f"Model: {meta['name']}") | |
| print(f"Author: {meta['author']}") | |
| print(f"Parameters (unique): {meta['params']}") | |
| print(f"Architecture: {meta['architecture']}") | |
| print() | |
| # Show the single parameter | |
| print("Registered nn.Parameters:") | |
| for name, p in model.named_parameters(): | |
| print(f" {name} = {p.item()}") | |
| print() | |
| print("Sanity checks:") | |
| for a, b in [ | |
| (0, 0), (1, 1), (5, 7), (99, 1), (999, 1), (9999999999, 1), | |
| (5555555555, 5555555555), (1234567890, 9876543210), | |
| (9999999999, 9999999999), | |
| ]: | |
| r = add(model, a, b) | |
| e = a + b | |
| print(("✓" if r == e else "✗"), a, "+", b, "=", r, "(expected", e, ")") | |
| print("\nFull verification (10K random, seed=2025)...") | |
| rng = random.Random(2025) | |
| edge_cases = [ | |
| (0, 0), (0, 1), (9999999999, 0), (9999999999, 1), (9999999999, 9999999999), | |
| (5000000000, 5000000000), (1111111111, 8888888889), | |
| (1234567890, 9876543210), (9999999999, 9999999999), (1, 9999999999), | |
| ] | |
| random_cases = [(rng.randint(0, 9999999999), rng.randint(0, 9999999999)) for _ in range(10000)] | |
| all_cases = edge_cases + random_cases | |
| correct = 0 | |
| start = time.time() | |
| for i, (a, b) in enumerate(all_cases): | |
| if add(model, a, b) == a + b: | |
| correct += 1 | |
| if (i + 1) % 2000 == 0: | |
| print(f" Progress: {i+1}/{len(all_cases)} ({correct}/{i+1} correct)") | |
| elapsed = time.time() - start | |
| acc = correct / len(all_cases) * 100 | |
| print(f"\nResults: {correct}/{len(all_cases)} ({acc:.2f}%)") | |
| print(f"Time: {elapsed:.1f}s") | |
| print(f"Status: {'QUALIFIED ✓' if acc >= 99 else 'NOT QUALIFIED ✗'}") |
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