Continuous Coin Betting Optimizer
Algorithms AIMech:CocobContinuousCoinBettingOptimizer DRAFT
Aliases: COCOB, COntinuous COin Betting, COCOB Optimizer, COCOB-Backprop
A learning-rate-free, dual-averaging stochastic subgradient optimization algorithm that reduces d-dimensional minimization of a function F(w) from initial point w_1 to betting on d continuous coins whose outcomes are the negative stochastic subgradients g_{t,i} in [-L_i, L_i] (E[g_t] in partial[-F(w_t)]): for each coordinate i, it accumulates absolute subgradient sum G_{t,i} = G_{t-1,i} + |g_{t,i}| (G_{0,i} = L_i), cumulative reward Reward_{t,i} = Reward_{t-1,i} + (w_{t,i} - w_{1,i}) g_{t,i}, and signed subgradient sum theta_{t,i} = theta_{t-1,i} + g_{t,i}, bets signed wealth fraction beta_{t,i} = (2 sigma(2 theta_{t,i} / (G_{t,i} + L_i)) - 1) / L_i where sigma(x) = 1 / (1 + exp(-x)), and updates parameters via w_{t+1,i} = w_{1,i} + beta_{t,i} (L_i + Reward_{t,i}), with deep-network variant COCOB-Backprop adapting L_{t,i} = max(L_{t-1,i}, |g_{t,i}|) and clamping Reward_{t,i} >= 0 online.
Identity Notes & Concept Scope
Distinct from adaptive learning-rate algorithms (AdaGrad, RMSProp, Adam, AdaDelta) that scale updates by a tuned base learning rate eta and from second-order or curvature-based tuners (YellowFin): COCOB eliminates the learning rate hyperparameter entirely by mapping iterate offsets w_{t,i} - w_{1,i} to bets proportional to accumulated gambler wealth L_i + Reward_{t,i} under Fenchel duality.
Claims & Grounded Evidence
4 Claims
Mechanism
#c-r621-scale-invariance-and-wealth-lower-bound
Multiplying all negative subgradients g_{t,i} and coordinate scales L_i by any positive constant c > 0 leaves the COCOB iterate sequence w_{t,i} invariant; moreover, because |beta_{t,i} g_{t,i}| < 1, gambler wealth Wealth_{t,i} = L_i + Reward_{t,i} remains strictly positive and satisfies the inductive data-dependent lower bound Wealth_{T,i} >= L_i exp(theta_{T,i}^2 / (2 L_i (G_{T,i} + L_i)) - sum_{j=1}^T |g_{j,i}| / (2 (G_{j-1,i} + L_i))) (Lemma 2 and Eq. 3).
Mechanism
#c-r621-weakly-quasi-convex-convergence-bound
By Fenchel-conjugate duality (Lemma 1), Theorem 1 proves that on any tau-weakly-quasi-convex objective F : R^d -> R with bounded stochastic subgradients |g_{t,i}| <= L_i, COCOB guarantees E[F(w_I)] - F(w*) <= sum_{i=1}^d (L_i + |w*_i - w_{1,i}| sqrt(E[L_i (G_{T,i} + L_i) ln(1 + (G_{T,i} + L_i)^2 (w*_i - w_{1,i})^2 / L_i^2)])) / (tau T), achieving the optimal O_tilde(||w* - w_1||_1 / sqrt(T)) parameter-free rate while exploiting gradient sparsity via G_{T,i}.
Application
#c-r621-cocob-backprop-online-scale-adaptation
To train deep neural networks where per-coordinate gradient bounds L_i are unknown a priori and vary across layers, COCOB-Backprop (Algorithm 2) updates L_{t,i} = max(L_{t-1,i}, |g_{t,i}|), enforces non-negative wealth Reward_{t,i} = max(Reward_{t-1,i} + (w_{t,i} - w_{1,i}) g_{t,i}, 0), and updates w_{t+1,i} = w_{1,i} + (theta_{t,i} / (L_{t,i} max(G_{t,i} + L_{t,i}, alpha L_{t,i}))) (L_{t,i} + Reward_{t,i}) with default alpha = 100 so the first update step has bounded magnitude |w_{2,i} - w_{1,i}| = 1 / alpha.
Limitation
#c-r621-known-scale-bound-and-overfitting-limitation
The theoretical convergence guarantee of Theorem 1 requires known a priori coordinate subgradient upper bounds |g_{t,i}| <= L_i; when L_{t,i} is estimated online in COCOB-Backprop, wealth positivity is no longer guaranteed without explicit clipping max(..., 0) and the formal regret guarantee no longer holds.
⚠️ Curated Limitations & Negative Results
- The exact Theorem 1 convergence guarantee requires known upper bounds L_i on coordinate subgradient magnitudes; the practical deep-learning variant COCOB-Backprop replaces L_i with running maxima L_{t,i} and lacks a formal convergence proof.
- Because COCOB rapidly minimizes training loss without manual learning-rate decay, overparameterized recurrent networks (such as word-level LSTMs on Penn Treebank) can exhibit test-perplexity overfitting unless paired with early stopping or regularization.
Artificial Intelligence Ontology (AIO) Grounding
Mapped AIO Classes
| AIO Target Class | Mapping Relation | Mapping Rationale |
|---|---|---|
AIO:ArtificialNeuralNetwork
Artificial Neural Network
|
related_match | COCOB and COCOB-Backprop are parameter-free stochastic gradient optimization algorithms designed for training deep neural networks without learning rates. |
Evidence Sources & Primary Literature
3 Sources| Source ID | Publication / Document | Type / Access | Reference & Checksum |
|---|---|---|---|
r621-primary-pdf
|
Francesco Orabona, Tatiana Tommasi
|
primary paper
full_text
|
ID: https://dblp.org/rec/conf/nips/OrabonaT17
sha256:ba246d027442…
|
r621-arxiv-abs
|
Francesco Orabona, Tatiana Tommasi
|
primary paper
abstract_only
|
ID: https://arxiv.org/abs/1705.07795
sha256:725a869c3a63…
|
r621-metadata-cr
|
Francesco Orabona, Tatiana Tommasi
|
primary paper
abstract_only
|
ID: https://dblp.org/rec/conf/nips/OrabonaT17
sha256:9491ec42db04…
|
Ontology & Grounding Topology
Open in interactive network graph →Curation Provenance
Curator: Antigravity
Method: ai_assisted
Model: Gemini
Created: 2026-10-19T11:44:00Z
Updated: 2026-10-19T11:44:00Z
Source File:
data/curated/CocobContinuousCoinBettingOptimizer.yaml
· Schema:
curated_concept.yaml
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