affaan-m/ECC · error

samples cannot be empty

Error message

samples cannot be empty

What it means

The `compare` function of the harness evaluation module rejects an empty slice of `PairedSample` inputs before running any statistical comparison. It needs at least one paired candidate/baseline measurement to compute means, deltas, and win rates; dividing by zero samples would be undefined. The check runs after internal threshold validation (`self.validate()`).

Solutions

1. Ensure at least one PairedSample is collected before calling compare.
2. Check policy configuration so minimum sample count is > 0 and seed generation actually yields values.
3. Guard the call site: return early or skip promotion evaluation when samples is empty.

Example fix

// before
let result = evaluator.compare(&samples)?;
// after
anyhow::ensure!(!samples.is_empty(), "no samples collected for comparison");
let result = evaluator.compare(&samples)?;

if samples.is_empty() {
    return Err(anyhow::anyhow!("no samples collected; cannot compare"));
}

match evaluator.compare(&samples) {
    Ok(c) => c,
    Err(e) if e.to_string().contains("samples cannot be empty") => {
        eprintln!("Skipping comparison: no samples collected");
        return Ok(());
    }
    Err(e) => return Err(e),
}

When it happens

Trigger: Calling `compare(&[])` (or `compare` with a Vec built from a filter that removed all samples), e.g. when a caller's seed generation or sampling loop produced no entries.

Common situations: Test harness runs where all samples were filtered out (e.g. all seeds skipped), a config file with an empty samples list, or a collection step that silently produced an empty vec before evaluation.

Understand the failure class

Background: "must not be empty", "cannot be empty" — required-field validation errors across open-source libraries — this error's family across 41 libraries.

Related errors

• at least one explicit seed is required
• At least one guided harness must be selected
• at least one non-empty
• at least one placement is required
• At least one video is required

AI-assisted analysis of affaan-m/ECC@8321021c54 (2026-09-16). Data as JSON: /api/errors/3611e07fae83796b. Report an issue: GitHub.

Appendix: source

Thrown at ecc2/src/harness_eval.rs:522

impl PromotionPolicy {
    pub fn validate(self) -> Result<()> {
        if self.min_samples == 0 {
            bail!("minimum samples must be positive");
        }
        if !self.min_mean_delta.is_finite() {
            bail!("minimum mean delta must be finite");
        }
        if !self.min_win_rate.is_finite() || !(0.0..=1.0).contains(&self.min_win_rate) {
            bail!("minimum win rate must be between 0 and 1");
        }
        Ok(())
    }

    pub fn compare(self, samples: &[PairedSample]) -> Result<Comparison> {
        self.validate()?;
        if samples.is_empty() {
            bail!("samples cannot be empty");
        }
        if samples
            .iter()
            .map(|sample| sample.seed)
            .collect::<BTreeSet<_>>()
            .len()
            != samples.len()
        {
            bail!("sample seeds must be unique");
        }
        if samples.iter().any(|s| {
            !s.candidate_score.is_finite()
                || !s.baseline_score.is_finite()
                || !(0.0..=1.0).contains(&s.candidate_score)
                || !(0.0..=1.0).contains(&s.baseline_score)
        }) {
            bail!("scores must be finite and between 0 and 1");
        }

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