moeru-ai/airi · error · Error

The AR-HMM iteration count must be a positive integer.

Error message

The AR-HMM iteration count must be a positive integer.

What it means

EM fitting of the AR-HMM iterates `options.iterations` times; a count below 1 or non-integer makes the loop meaningless or impossible. The library validates this at the entry point before any fitting work.

Source

Thrown at packages/motion-driver-magic/src/ar-hmm.ts:360

  for (let row = 0; row < rowCount - 1; row++) {
    const values = alpha[row].flatMap((value, state) => parameters.states.map(
      (_nextStateModel, nextState) => value + logTransitions[state][nextState] + emissions[row + 1][nextState] + beta[row + 1][nextState],
    ))
    const normalization = logSumExp(values)
    for (let state = 0; state < options.stateCount; state++) {
      for (let nextState = 0; nextState < options.stateCount; nextState++)
        transitionCounts[state][nextState] += Math.exp(values[state * options.stateCount + nextState] - normalization)
    }
  }
  return { gamma, transitionCounts, logLikelihood }
}

/** Creates a linear Gaussian AR-HMM model with deterministic clustering and EM updates. */
export function createArHmmModel(sequence: TrainingSequence, options: FitOptions): ArHmmModel {
  if (options.stateCount < 2 || !Number.isInteger(options.stateCount))
    throw new Error('The AR-HMM state count must be an integer greater than one.')
  if (options.iterations < 1 || !Number.isInteger(options.iterations))
    throw new Error('The AR-HMM iteration count must be a positive integer.')

  const sourceModel = fitVarParameters(sequence, {
    order: options.order,
    ridge: options.ridge,
  })
  const rowCount = sourceModel.trainingFrames.length - options.order
  if (rowCount < options.stateCount * (sourceModel.featureCount + 1))
    throw new Error('The current motion is too short for this AR-HMM shape.')

  const clusterFeatures = createClusterFeatures(sourceModel.trainingFrames, options.order)
  const assignments = initializeAssignments(clusterFeatures, options.stateCount)
  let expectation = createInitialExpectations(assignments, options.stateCount)
  let stateParameters = maximizeParameters(sourceModel, expectation, options)
  const logLikelihoods: number[] = []
  for (let iteration = 0; iteration < options.iterations; iteration++) {
    expectation = expectationStep(sourceModel, stateParameters, options)
    logLikelihoods.push(expectation.logLikelihood)
    stateParameters = maximizeParameters(sourceModel, expectation, options)

View on GitHub (pinned to 9c213115f8)

Solutions

1. Pass an integer `iterations >= 1`.
2. Coerce computed values: `Math.max(1, Math.round(budget / costPerIteration))`.
3. Validate the options object with a schema (integer, minimum 1) before calling.
4. Use the documented default iterations instead of a hand-computed value when unsure.

Example fix

// before
createArHmmModel(seq, { stateCount: 3, iterations: 0 })
// after
createArHmmModel(seq, { stateCount: 3, iterations: Math.max(1, Math.round(rawIterations)) })

function isValidIterations(n: unknown): n is number {
  return typeof n === 'number' && Number.isInteger(n) && n >= 1
}

try {
  const model = createArHmmModel(seq, options)
} catch (error) {
  if (error instanceof Error && error.message.includes('iteration count')) {
    return createArHmmModel(seq, { ...options, iterations: 10 })
  }
  throw error
}

When it happens

Trigger: Calling `createArHmmModel(seq, { iterations: 0 })`, negative values, or a non-integer (e.g. 1.5). Also when iterations is computed dynamically (e.g. scaled by a quality factor) without rounding.

Common situations: A 'fast mode' config setting iterations to 0 intending 'auto'; dividing a time budget by per-iteration cost producing a fractional count; JSON config parsed as float (e.g. 3.0 stored as 3 but 2.5 typed by hand).

Related errors

• The AR-HMM state count must be an integer greater than one.
• The current motion is too short for this AR-HMM shape.
• The motion sample rate must be positive.
• The VAR order must be a positive integer.
• mutexAcquireTimeout must be a positive finite number

AI-assisted analysis of moeru-ai/airi@9c213115f8 (2026-09-02). Data as JSON: /api/errors/4422b0fb0e233992. Report an issue: GitHub.