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@JagNL
Created February 27, 2026 04:59
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TinyAdder-1: 1-parameter hand-coded transformer for 10-digit addition (AdderBoard submission)
#!/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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