Determinantal Exclusion Router
Implementation & benchmark of arXiv:2607.28807 — Exact Results for the Symmetric Dyson Exclusion Process
Source paper: Exact Results for the Symmetric Dyson Exclusion Process arXiv:2607.28807 ⓘ · analyzed Aug 31, 2026
AI-generated research hypothesis, automatically tested. Not peer-reviewed.
Idea description
Replace independent softmax expert choices with a collision-free Markov router whose particles occupy expert positions on a one-dimensional or circular index lattice. A particle can move only to an empty neighboring expert, and the move rate contains a product of sine ratios that globally repels nearby assignments; this should reduce expert collapse and produce more evenly spread routing without requiring a separate pairwise diversity loss.
Formulas
Mathematical statement
Let L be the number of experts arranged on a periodic lattice, N the number of simultaneously routed tokens or routing slots, and eta={x_1,...,x_N} the occupied expert positions. For an allowed move of particle i from x_i to x_i plus or minus 1, the SDEP rate is c_i^plus-or-minus(eta)=w times the product over j not equal to i of sin(pi times (x_i plus-or-minus 1 minus x_j) divided by L) divided by sin(pi times (x_i minus x_j) divided by L), where w>0 sets the time scale. Moves into occupied sites have rate zero. Define the continuous-time generator Q by Q[eta,eta^(i,s)]=c_i^s(eta) and Q[eta,eta]=minus the sum over i and s of c_i^s(eta). The transition operator is P_t=exp(tQ). The useful transferable property is hard exclusion combined with global repulsion; the exact determinantal evolution can be used as a reference or approximated by short-time sampling.
Implementation notes
Integrate the mechanism at an MoE routing layer after computing token-to-expert logits z[b,e]. For each routing group, initialize a collision-free configuration eta from the top-N logits, where each occupied lattice position represents one routing slot. Run m discrete Gillespie-like updates. At every update, compute both rates for every occupied position using the sine-product formula, multiply each rate by exp(beta times the destination-logit minus the current-logit), mask destinations already occupied, sample one move proportional to the resulting rates, and update eta. Dispatch tokens according to the final occupied positions. Use sums of log absolute sine values rather than direct products, handle periodic distances explicitly, and add a small numerical floor to sine magnitudes. The paper supplies the exclusion geometry and transition rates; the logit bias, finite-step sampler, and token-grouping rule are neural adaptations. The first cheap test should use a small Switch-Transformer on WikiText-103 or CIFAR-100, with ordinary top-1 routing and top-k routing plus load-balancing loss as baselines at equal expert FLOPs. Record expert-load coefficient of variation, collision rate, validation loss, and routing entropy. The prediction is that collision rate is exactly zero, load variance decreases with update count m and repulsion scale w until logits dominate, and a crossover occurs when w divided by the standard deviation of logits is comparable to the inverse temperature beta. Locate this crossover and test whether it shifts by less than 20 percent across random seeds.
Verification
This idea has not been verified yet.
Verification happens in two stages: Stage 1 — a mechanism check on a toy system confirms the claimed mathematical phenomenon reproduces; Stage 2 — a benchmark implements the idea on a real (small) neural network task and compares it against a tuned baseline over 8 paired seeds with a permutation test.
Artifacts
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