Pith. sign in

REVIEW 3 major objections 5 minor 1 cited by

Action-List Reinforcement Learning Syndrome Decoding for Binary Linear Block Codes

T0 review · 3 major / 5 minor · reviewed 2026-08-06 · deepseek-v4-flash

Pith's one-line read This paper claims that a reinforcement-learning decoder guided by Deep Q-Network values and run as a short action list can bring the Tanner (155,64,20) code close to bounded-distance decoding with radius 10, correcting most error patterns…

desk verdict New RL decoding recipe with a real action-list idea, but a false theorem and unaudited FER curves make the headline BDD(10) claim conditional. read the letter →

arxiv 2507.17893 v2 pith:5OUW5ABS submitted 2025-07-23 cs.IT cs.AIcs.LGmath.IT

classification cs.ITcs.AIcs.LGmath.IT MSC 94B35
keywords reinforcementlearningaction-listdecodingbeamautomorphismgroupbit-flippinglinearblockcodesQC-LDPCboundeddistance
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

The paper proposes a general recipe for turning binary linear block-code decoding into a reinforcement-learning task: the state is the syndrome of the received word, an action is flipping one bit, and a learned Q-function guides the decoder to the all-zero syndrome. To keep the state space tractable, it truncates the MDP to a Hamming ball of radius $w$ around codewords and shows that a Deep Q-Network trained on this smaller space corrects errors outside the ball. It then adds action-list decoding, a beam-search-like scheme over the Q-values, and uses the code's automorphism group to permute received words, because RL bit-flipping rules are position-dependent even on a symmetric channel. On the Tanner $(155,64,20)$ code, list size 5 plus these permutations approaches bounded-distance decoding with radius 10, correcting most error patterns of weight up to 10 although the code's guaranteed correction radius is nine; a feedback variant wraps an existing bit-flipping decoder and trains RL only on that decoder's failures.

What carries the argument

The machinery has four moving parts. The truncated MDP replaces the full syndrome space by the set of syndromes reachable from a Hamming ball $B(w)$ of radius $w$ around codewords, so the agent trains only on the most probable error patterns and the state count shrinks from $2^{n-k}$ to roughly the number of words within the ball. A Deep Q-Network approximates the action-value function $Q(s,a)$ for flipping bit $a$ in syndrome state $s$; the reward is a small penalty per flip plus a terminal bonus for reaching the all-zero syndrome, so good paths are short bit-flip sequences. Action-list decoding is beam search over these Q-values: at each state it keeps the top $k$ actions, extends only paths whose next Q-value exceeds the parent's score, and prunes back to the top $k$ until a zero syndrome appears, which suppresses the oscillation that greedy use of approximate Q-values causes. The automorphism group of the quasi-cyclic code supplies cyclic permutations of bit positions that are applied to the received word and inverted on the output; because RL bit-flipping rules are position-dependent, permuting the word lets the same learned rules handle many error patterns. A feedback decoder wraps an existing bit-flipping decoder and trains the RL block only on the failure region, so the state space stays small while the correctable region expands.

What would settle it

Run the trained list-size-5-plus-permutations decoder on a large set of random transmitted codewords of the Tanner code, not just the all-zero word, and compare the measured frame error rate; if it rises materially, the claimed approach to bounded-distance radius-10 decoding is conditional on the all-zero test. A second check is to enumerate all error patterns of weight exactly 10 and confirm every one is corrected, since bounded-distance decoding with radius 10 corrects all of them.

Watch

Extended reading notes

Core claim

The central claim is that approximate Q-values can be turned into a reliable decoder by keeping a short list of candidate flipping paths instead of one greedy action. For the Tanner $(155,64,20)$ code, the action-list decoder with list size 5, combined with cyclic permutations from the automorphism group, closely approaches bounded-distance decoding with radius 10: it corrects most error patterns of weight up to 10, beyond the code's guaranteed correction radius of $t=9$. The same truncated-MDP and action-list construction is claimed to apply to any binary linear block code, and the feedback decoder is claimed to lift any existing decoder by training RL only on the error patterns that decoder fails to correct.

Load-bearing premise

The reported error rates assume the decoder is symmetric enough that transmitting the all-zero codeword represents every codeword; the paper's own account of position-dependent RL rules makes that symmetry assumption doubtful.

Editorial extensions

If this is right

  • A Deep Q-Network trained inside a small Hamming ball generalizes to error patterns of higher weight that it never saw, so the RL state space does not need to cover the full syndrome space.
  • The action-list decoder with list size 5 plus cyclic automorphisms brings the Tanner $(155,64,20)$ code close to bounded-distance decoding with radius 10, so most weight-10-or-less error patterns are corrected despite a guaranteed radius of $t=9$.
  • The feedback decoder gives a direct route to improving an existing iterative decoder: train the RL block on the failure syndromes only, and its correctable region expands while training complexity stays low.
  • Because the scheme is formulated for arbitrary binary linear codes and any base decoder, the same pieces transfer to other short-block codes and other decoders.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • If the position dependence that motivates the automorphism trick is real, then the all-zero-codeword evaluation is not automatically representative of average frame error rate; averaging over random transmitted codewords or over the automorphism orbit would tell whether part of the reported gain is an artifact of the test condition.
  • The monotone pruning rule (extend only when the next Q-value exceeds the parent's score) is an extra assumption about approximate Q-values; a natural variant is to keep the top $k$ successor Q-values regardless of monotonicity and compare robustness.
  • The same truncated-MDP and action-list pattern should transfer to soft-decision channels and to other learned decoders, since the feedback wrapper only needs the base decoder's failure syndromes rather than its internals.
Share X Bluesky LinkedIn Reddit HN

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

3 major / 5 minor

Summary. This paper proposes a reinforcement-learning framework for syndrome-based bit-flipping decoding of binary linear block codes. It introduces a truncated MDP that restricts the state space to syndromes inside a Hamming ball of radius w, an action-list decoder that uses DQN Q-values to maintain a beam of k candidate flip sequences, a feedback decoder that attaches an RL block to an existing decoder, and an automorphism-group reduction for QC-LDPC codes based on Burnside counting and lexicographic canonical representatives. Numerical results are reported for the Tanner (155,64,20) code and a random (24,6,10) code. The main claim is that action-list decoding with list size 5 combined with cyclic automorphisms closely approaches BDD(10), and that the DQN generalizes to error patterns beyond its training radius.

Significance. If the central claims held, the action-list mechanism would be a useful way to convert imperfect DQN policies into low-FER decoders for short and moderate-length codes, and the automorphism-based state reduction could be valuable for QC-LDPC training. The paper's strengths are its explicit pseudocode, the use of concrete BDD baselines, and the error-floor estimation methodology. However, the key experimental evidence is not auditable from the preprint: there is no code, no trial counts, no seeds, and no error bars. In addition, the BDD(10) baseline is not a well-defined bounded-distance decoding curve for a code of minimum distance 20, and the lower bound in Theorem 3 is not proved. The paper is therefore promising but not yet ready for publication.

major comments (3)
  1. [Section IX-B, Theorem 3 (Eq. (43)) and Appendix D] The lower bound in Theorem 3 is not established by the proof. The Burnside calculation in Appendix D counts orbits of all binary colorings of the jp check-node coordinates, giving Nfull, but the valid syndrome space is the rank(H)-dimensional subspace im(H), not the full coloring set. The step that divides by 2^{m-rank(H)} is asserted in one sentence (the coloring of redundant rows can be identified through independent row colorings) and is not a derivation. The upper bound Ns ≤ Nfull follows from the subset relation, but the lower bound does not follow from Burnside's lemma. The theorem should either be proved or restated as an upper bound; as written, the state-space reduction claim in Section IX is unsupported.
  2. [Section II-A (Eq. (1)), Figs. 7-8] The baseline labeled BDD(w=10) is not the frame error rate of a valid bounded-distance decoder for the Tanner code. Since dmin=20, t=9, and there exist pairs of codewords at distance 20, a weight-10 error pattern can be equidistant from two codewords; such patterns are not uniquely correctable by any decoder. Equation (1) counts all weight-i patterns for i≤10 as corrected, so for w=10 it is a genie-aided bound, not a BDD curve. The headline claim that the action-list decoder closely approaches BDD(10) is therefore ambiguous. Please define the baseline explicitly as a genie-aided bound, or compute the true BDD(10) performance with ties taken into account.
  3. [Section X (Figs. 5-9)] The empirical claims cannot be audited from the manuscript. There is no code, no dataset, no random seed, no number of Monte Carlo trials, and no confidence intervals. Several FER curves extend below 10^-8 (Figs. 7 and 8), which would require at least 10^10 trials per point; the paper does not state how these curves were obtained. The claims that DQN generalizes to untrained states and that list-size-5 plus automorphisms approaches BDD(10) rest entirely on these curves. Please provide the simulation protocol and either release the code and data or include statistical error bars.
minor comments (5)
  1. [Section V and Section IX] The all-zero-codeword evaluation is actually justified for these syndrome-based decoders: for any transmitted codeword c, the syndrome of y=c+e equals the syndrome of e, so the same bit-flip sequence is applied and the frame error decision is identical. The anisotropy discussed in Section IX concerns dependence on the error-pattern position, not dependence on the transmitted codeword. The paper should state this explicitly, since the current wording invites confusion.
  2. [Eqs. (13), (21), (29), (31)] Several reward definitions contain is s instead of if s; please correct these typos.
  3. [Theorem 1 and Appendix A] The displayed product is ambiguous (it should presumably be i^{binom(n,i)}), and the proof text describes i*binom(n,i) possible optimal actions and then multiplies over i. The notion of distinct optimal policy is never defined. Please clarify the statement and proof.
  4. [Section V, Eq. (12)] Equation (12) counts error patterns, not necessarily distinct syndromes. Equality holds when all error patterns of weight at most w have distinct syndromes (true for the Tanner code for w≤9 because t=9), but the condition should be stated for general codes.
  5. [Figure captions and Section X] The captions of Figs. 7 and 8 use beam sizes while the text uses list sizes; please unify the terminology and add the number of trials to each figure caption.

Circularity Check

0 steps flagged · score 0.0 of 10

No significant circularity: the decoder performance claims are empirical Monte Carlo comparisons against an external BDD baseline, and the QL-vs-BDD agreement is an explicitly designed convergence check, not a fitted prediction.

full rationale

Walking the paper's derivation chain, the truncated MDP in Section V defines the state space as syndromes of error patterns within a Hamming ball of radius w and explicitly states that this is 'a bounded-distance decoding version of the MDP, which, at best, achieves the performance corresponding to the bounded-distance error probability.' The reported agreement between Q-learning with w = {1,2,3} and BDD(w) is therefore a convergence sanity check, not a predicted result; the optimal policy for those states is BDD by construction, and the paper presents it that way. The action-list decoder of Section VII is a beam search over Q-values, and its comparison against BDD(9) and BDD(10) is an external, falsifiable Monte Carlo result that does not reduce to any fitted parameter or to the training reward. The feedback decoder error-floor estimates use the general formula in Equation (2) with the decoder's own uncorrectable-error enumerator; this is self-referential but standard extrapolation, not circular. The counting and lower-bound theorems are independent combinatorial arguments. The only same-author citation, [15], is not load-bearing; it appears alongside an independent prior work as background on RL bit-flipping formulations. The one notable tension is that Section V justifies all-zero-codeword evaluation via Richardson-Urbanke Lemma 1, which requires decoder symmetry, while Section IX acknowledges that 'the sequential nature of reinforcement learning introduces anisotropy–position dependent bit-flipping rules.' This is a benchmark-validity threat to the reported FER curves, not a circular reduction: the BDD baseline and the decoder's success counts are external to the training objective. No step reduces, by the paper's own equations or by self-citation, to its own inputs.

Assumptions & free parameters 4 free parameters · 5 assumptions · 0 invented entities

The central performance claims rest on several modeling choices: the truncated Hamming ball radius w, the action-list size k, the discount factor, and the maximum iteration length. These are hand-chosen and materially affect the reported results; they are not derived from first principles. The evaluation additionally assumes decoder symmetry for all-zero-codeword testing, which the paper's own anisotropy discussion undermines. No new physical entities are introduced.

free parameters (4)
  • Hamming ball radius w
    Selected from {1,...,7} for the truncated MDP; controls state space size and training complexity, and the decoder is only trained to correct errors up to weight w.
  • Action-list/list size k
    Beam width in the action-list decoder, chosen from {1,5,10,20,30,40}; reported performance improves with k.
  • Discount factor gamma
    Set to 0.9 in Figures 6-8 and 0.7 in Figures 5 and 9; chosen by hand to tune Q-value distinguishability.
  • Maximum episode length L / Dmax = 10
    Used in the reward function penalty -1/L and as the maximum search depth; chosen to bound decoding delay.
assumptions (5)
  • domain assumption All-zero codeword assumption (decoder symmetry)
    Invoked in Section V to justify evaluating only the all-zero codeword; but RL policies may be asymmetric, and Section IX acknowledges position-dependent behavior, so the assumption may not hold for the learned decoder.
  • standard math Convergence of Q-learning to the optimal policy
    Used in Theorems 1 and 2, citing Sutton and Barto; fine for tabular Q-learning under standard conditions, but DQN only approximates this.
  • ad hoc to paper DQN generalization to untrained states
    The decoder relies on Q-values for states outside the training Hamming ball; the paper observes generalization empirically (Section X) but provides no theoretical justification.
  • domain assumption QC-LDPC automorphism group is C_p semidirect C_j
    Section IX uses the group-structured QC-LDPC code construction from Tanner et al.; standard for this code family.
  • domain assumption Error floor estimation using only lowest-weight uncorrectable patterns
    Equations (2)-(3) approximate FER in the error floor; standard asymptotic approximation, but not exact at moderate SNR.

how reviews work

0 comments
Cite this review

Pith. "Pith review of Action-List Reinforcement Learning Syndrome Decoding for Binary Linear Block Codes." pith.science (2026). https://pith.science/paper/5OUW5ABS

@misc{pith2026250717893,
  author       = {Pith},
  title        = {Pith review of: Action-List Reinforcement Learning Syndrome Decoding for Binary Linear Block Codes},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/5OUW5ABS}},
  note         = {Machine review of arXiv:2507.17893}
}
read the original abstract

This paper explores the application of reinforcement learning techniques to enhance the performance of decoding of linear block codes based on flipping bits and finding optimal decisions. We describe the methodology for mapping the iterative decoding process into Markov Decision Processes (MDPs) and propose different methods to reduce the number of states in the MDP. A truncated MDP is proposed to reduce the number of states in the MDP by learning a Hamming ball with a specified radius around codewords. We then propose a general scheme for reinforcement learning based decoders applicable to any class of codes to improve the performance of decoders. We call this scheme an action-list decoding. We design an action-list decoder based on the Deep-Q network values that substantially enhance performance. We also get benefit of automorphism group of code to further improve the code performance. Additionally, we propose a feedback-based method to exploit and enhance the performance of existing high-performing decoders by applying reinforcement learning algorithms after the existing decoders. These approaches effectively reduces the complexity of the reinforcement learning block. Finally, we present experimental results for the Low-Density Parity Check (LDPC) codes over the Binary Symmetric Channel (BSC) to demonstrate the efficiency of the proposed methods.

Figures

Figures reproduced from arXiv: 2507.17893 by the authors.

Figure 1
Figure 1. Q-values as a Function of Time Steps to Terminal State. [PITH_FULL_IMAGE:figures/full_fig_p005_1.png] view at source ↗
Figure 2
Figure 2. 2-Depths expansion of Action-List Algorithm. process is repeated until either a valid codeword is found or the predefined number of steps is reached. In the action￾list algorithm, the policy network is evaluated k times at each depth, followed by k sorting operations. In the next section, we aim to leverage the performance of existing well￾designed decoders and refine their state space to improve their performance u… view at source ↗
Figure 3
Figure 3. Feedback based Reinforcement Learning decoder. [PITH_FULL_IMAGE:figures/full_fig_p007_3.png] view at source ↗
Figures from the paper (6 more)
Figure 4
Figure 4. Figure 4: Feedback based Reinforcement Learning decoder. [PITH_FULL_IMAGE:figures/full_fig_p007_4.png]
Figure 5
Figure 5. Figure 5: Simulation results for tanner code of Bit-Flipping decoder and learned Bit-Flipping based on Q-table for truncated [PITH_FULL_IMAGE:figures/full_fig_p011_5.png]
Figure 6
Figure 6. Figure 6: Simulation results for a binary random linear code with parameters ( [PITH_FULL_IMAGE:figures/full_fig_p011_6.png]
Figure 7
Figure 7. Figure 7: Simulation results for Tanner code with Deep Q-Network decoder and different beam sizes [PITH_FULL_IMAGE:figures/full_fig_p012_7.png]
Figure 8
Figure 8. Figure 8: Simulation results for Tanner code with Deep Q-Network decoder and different beam sizes [PITH_FULL_IMAGE:figures/full_fig_p012_8.png]
Figure 9
Figure 9. Figure 9: Simulation results for the Tanner code using the Bit-Flipping decoder and and its Q-learning and Deep-Q network [PITH_FULL_IMAGE:figures/full_fig_p013_9.png]

Discussion (0). Continue with ORCID to comment.

Forward citations

Cited by 1 Pith paper

Reviewed papers in the Pith corpus that reference this work. Sorted by Pith novelty score. Full citation record

  1. Multistage Rewinding Decoder for QLDPC Codes

    quant-ph 2026-08 conditional novelty 5.0 of 10

    A multistage rewinding decoder that forces suspicious qubit values in a beam search improves QLDPC decoding over normalized min-sum and approaches BP-OSD-10 performance.

Reference graph

Works this paper leans on

24 extracted references · 24 canonical work pages · cited by 1 Pith paper

  1. [1]

    The Viterbi Algorithm,

    G. Forney, “The Viterbi Algorithm,” Proceedings of the IEEE , vol. 61, no. 3, pp. 268–278, March 1973

  2. [2]

    Optimal Decoding of Linear Codes for Minimizing Symbol Error Rate,

    L. Bahl, J. Cocke, F. Jelinek, and J. Raviv, “Optimal Decoding of Linear Codes for Minimizing Symbol Error Rate,” IEEE Transactions on Information Theory , vol. 20, no. 2, pp. 284–287, March 1974

  3. [3]

    Soft-Decision Decoding of Linear Block Codes Based on Ordered Statistics,

    M. Fossorier and S. Lin, “Soft-Decision Decoding of Linear Block Codes Based on Ordered Statistics,” IEEE Transactions on Information Theory, vol. 41, no. 5, pp. 1379–1396, September 1995

  4. [4]

    List Decoding of Polar Codes,

    I. Tal and A. Vardy, “List Decoding of Polar Codes,” IEEE Transactions on Information Theory , vol. 61, no. 5, pp. 2213–2226, May 2015

  5. [5]

    Factor Graphs and the Sum-Product Algorithm,

    F. Kschischang, B. Frey, and H.-A. Loeliger, “Factor Graphs and the Sum-Product Algorithm,” IEEE Transactions on Information Theory , vol. 47, no. 2, pp. 498–519, February 2001

  6. [6]

    Complementary Exclusion of Full Polynomials to Enable Dual List Decoding of Convolutional Codes,

    Z. Qu, A. Antonini, W. Sui, E. Min, A. Yang, and R. D. Wesel, “Complementary Exclusion of Full Polynomials to Enable Dual List Decoding of Convolutional Codes,” in IEEE International Symposium on Information Theory (ISIT) , July 2024, pp. 1776–1781

  7. [7]

    Performance Improvement of Space Missions Using Convolutional Codes by CRC-Aided List Viterbi Algorithms,

    R. Schiavone, R. Garello, and G. Liva, “Performance Improvement of Space Missions Using Convolutional Codes by CRC-Aided List Viterbi Algorithms,” IEEE Access, vol. 11, pp. 55 925–55 937, January 2023

  8. [8]

    Learning to Decode Linear Codes Using Deep Learning,

    E. Nachmani, Y . Be’ery, and D. Burshtein, “Learning to Decode Linear Codes Using Deep Learning,” in 54th Annual Allerton Conference on Communication, Control, and Computing (Allerton) , September 2016, pp. 341–346

Show all 24 references
  1. [9]

    On Deep Learning-Based Channel Decoding,

    T. Gruber, S. Cammerer, J. Hoydis, and S. Ten Brink, “On Deep Learning-Based Channel Decoding,” in 51st Annual Conference on Information Sciences and Systems (CISS) . IEEE, March 2017, pp. 1–6. 12 10-2 10-110-10 10-8 10-6 10-4 10-2 100 FER list size=1 list size=5 list size=10 ...

  2. [10]

    Deep Learning for De- coding of Linear Codes - A Syndrome-Based Approach,

    A. Bennatan, Y . Choukroun, and P. Kisilev, “Deep Learning for De- coding of Linear Codes - A Syndrome-Based Approach,” in IEEE International Symposium on Information Theory (ISIT) , June 2018, pp. 1595–1599

  3. [11]

    Neural Offset Min-Sum Decoding,

    L. Lugosch and W. J. Gross, “Neural Offset Min-Sum Decoding,” in IEEE International Symposium on Information Theory (ISIT), June 2017, pp. 1361–1365

  4. [12]

    Designing Finite Alphabet Iterative Decoders of LDPC Codes Via Recurrent Quantized Neural Networks,

    X. Xiao, B. Vasi ´c, R. Tandon, and S. Lin, “Designing Finite Alphabet Iterative Decoders of LDPC Codes Via Recurrent Quantized Neural Networks,” IEEE Transactions on Communications , vol. 68, no. 7, pp. 3963–3974, July 2020

  5. [13]

    Generalization Bounds for Neural Belief Propagation Decoders,

    S. Adiga, X. Xiao, R. Tandon, B. Vasi ´c, and T. Bose, “Generalization Bounds for Neural Belief Propagation Decoders,” IEEE Transactions on Information Theory, vol. 70, no. 6, pp. 4280–4296, 2024

  6. [14]

    Reinforce- ment Learning for Channel Coding: Learned Bit-Flipping Decoding,

    F. Carpi, C. H ¨ager, M. Martal`o, R. Raheli, and H. D. Pfister, “Reinforce- ment Learning for Channel Coding: Learned Bit-Flipping Decoding,” in 2019 57th Annual Allerton Conference on Communication, Control, and Computing (Allerton). IEEE, 2019, pp. 922–929

  7. [15]

    Reinforcement Learning Assisted Decoding,

    M. Taghipour, A. K. Pradhan, and B. Vasi ´c, “Reinforcement Learning Assisted Decoding,” in International Telemetry Conference 2024, Octo- ber 2024, pp. 1–5

  8. [16]

    Belief Propagation Decoding of Short Graph-Based Channel Codes via Reinforcement Learning,

    S. Habib, A. Beemer, and J. Kliewer, “Belief Propagation Decoding of Short Graph-Based Channel Codes via Reinforcement Learning,” IEEE Journal on Selected Areas in Information Theory , vol. 2, no. 2, pp. 627–640, April 2021

  9. [17]

    Lin and D

    S. Lin and D. J. Costello, Error Control Coding . Prentice Hall Scarborough, 2001, vol. 2, no. 4

  10. [18]

    R. S. Sutton and A. G. Barto, Reinforcement Learning: An Introduction. MIT Press Cambridge, 2018

  11. [19]

    The Capacity of Low-Density Parity-Check Codes under Message-Passing Decoding,

    T. J. Richardson and R. L. Urbanke, “The Capacity of Low-Density Parity-Check Codes under Message-Passing Decoding,” IEEE Transac- tions on Information Theory , vol. 47, no. 2, pp. 599–618, 2001

  12. [20]

    Simulation-Guided Beam Search for Neural Combinatorial Optimization,

    J. Choo, Y .-D. Kwon, J. Kim, J. Jae, A. Hottung, K. Tierney, and Y . Gwon, “Simulation-Guided Beam Search for Neural Combinatorial Optimization,” in Advances in Neural Information Processing Systems , vol. 35. Curran Associates, Inc., 2022, pp. 8760–8772

  13. [21]

    A Class of Group-Structured LDPC Codes,

    R. M. Tanner, D. Sridhara, and T. Fuja, “A Class of Group-Structured LDPC Codes,” in Proc. ISTA, July 2001, pp. 365–370. 13 10-8 10-6 10-4 10-2 10010-12 10-10 10-8 10-6 10-4 10-2 100 FER BF QL Feedback(w=2) QL Feedback(w=3) DQ Feedback(w=2) DQ Feedback(w=3) DQ Feedback(w=4) FE...

  14. [22]

    Lexicographically Least Circular Substrings,

    K. S. Booth, “Lexicographically Least Circular Substrings,” Information Processing Letters, vol. 10, no. 4, pp. 240–242, July 1980. APPENDIX A PROOF OF THEOREM 1 Theorem 1. The number of distinct optimal policies, or proposed decoders, for the Binary Symmetric channel is at le...

  15. [23]

    Identity: e·x = x, ∀x ∈ X, where e ∈ G is the identity element

  16. [24]

    Definition 3

    Associativity: (gh) · x = g · (h · x), ∀g, h∈ G and ∀x ∈ X. Definition 3. (Orbit). The orbit of an element x ∈ X under the action of a group G is defined as Orb(x) = {g · x : g ∈ G} ⊆X. (53) It consists of all elements of X to which x can be mapped through the action of elemen...

Pith tools

Reviewed August 6, 2026 · model on record in the stance chip above.