fsci-conformance 0.3.0

#![forbid(unsafe_code)]
//! Live SciPy differential coverage for `scipy.stats.halfnorm`.
//!
//! Resolves [frankenscipy-pi22c]. HalfNormal has anchor tests
//! in `fsci-stats/src/lib.rs` but no dedicated scipy diff
//! harness. fsci's `HalfNormal` is parameterless (standard
//! half-normal); the harness pins scipy to halfnorm(loc=0,
//! scale=1).
//!
//! 11 x-values × 3 families (pdf, cdf, sf) + 7 ppf cases via
//! subprocess.
//!
//! pdf is closed-form Gaussian; cdf uses erf(x/√2); sf uses
//! erfc(x/√2) (fsci's f66lp closed-form survival fix that
//! preserves deep-right-tail value where 1-cdf collapses to 0).
//! ppf uses ndtri rational, hold to 1e-7 rel.

use std::collections::{BTreeMap, HashMap};
use std::fs;
use std::io::Write;
use std::path::PathBuf;
use std::process::Stdio;
use std::time::{Instant, SystemTime, UNIX_EPOCH};

use fsci_conformance::{ArmCounts, CompareLedger};
use fsci_stats::{ContinuousDistribution, HalfNormal};
use serde::{Deserialize, Serialize};

const PACKET_ID: &str = "FSCI-P2C-007";
const PDF_TOL: f64 = 1.0e-13;
// erf/erfc helpers land ~2.7e-13 off scipy at x≈5 (z≈3.5).
// Bump cdf/sf to 5e-13 to absorb that floor.
const CDF_TOL: f64 = 5.0e-13;
const SF_TOL: f64 = 5.0e-13;
const PPF_TOL_REL: f64 = 1.0e-7;
const REQUIRE_SCIPY_ENV: &str = "FSCI_REQUIRE_SCIPY_ORACLE";

#[derive(Debug, Clone, Serialize)]
struct PointCase {
    case_id: String,
    x: f64,
}

#[derive(Debug, Clone, Serialize)]
struct PpfCase {
    case_id: String,
    q: f64,
}

#[derive(Debug, Clone, Serialize)]
struct OracleQuery {
    points: Vec<PointCase>,
    ppf: Vec<PpfCase>,
}

#[derive(Debug, Clone, Deserialize)]
struct PointArm {
    case_id: String,
    pdf: Option<f64>,
    cdf: Option<f64>,
    sf: Option<f64>,
}

#[derive(Debug, Clone, Deserialize)]
struct PpfArm {
    case_id: String,
    ppf: Option<f64>,
}

#[derive(Debug, Clone, Deserialize)]
struct OracleResult {
    points: Vec<PointArm>,
    ppf: Vec<PpfArm>,
}

#[derive(Debug, Clone, Serialize)]
struct CaseDiff {
    case_id: String,
    family: String,
    abs_diff: f64,
    pass: bool,
}

#[derive(Debug, Clone, Serialize)]
struct DiffLog {
    test_id: String,
    category: String,
    case_count: usize,
    compared: BTreeMap<String, ArmCounts>,
    max_abs_diff: f64,
    pass: bool,
    timestamp_ms: u128,
    duration_ns: u128,
    cases: Vec<CaseDiff>,
}

fn output_dir() -> PathBuf {
    PathBuf::from(env!("CARGO_MANIFEST_DIR")).join(format!("fixtures/artifacts/{PACKET_ID}/diff"))
}

fn ensure_output_dir() {
    fs::create_dir_all(output_dir()).expect("create halfnorm diff output dir");
}

fn timestamp_ms() -> u128 {
    SystemTime::now()
        .duration_since(UNIX_EPOCH)
        .map_or(0, |d| d.as_millis())
}

fn emit_log(log: &DiffLog) {
    ensure_output_dir();
    let path = output_dir().join(format!("{}.json", log.test_id));
    let json = serde_json::to_string_pretty(log).expect("serialize halfnorm diff log");
    fs::write(path, json).expect("write halfnorm diff log");
}

fn generate_query() -> OracleQuery {
    // x walks 0+ through the deep right tail (z=8 puts sf in
    // the ~1e-15 territory where erfc precision matters).
    let xs = [
        1.0e-12_f64,
        0.01,
        0.1,
        0.5,
        1.0,
        1.5,
        2.0,
        3.0,
        5.0,
        7.0,
        8.0,
    ];
    let qs = [0.001_f64, 0.01, 0.1, 0.5, 0.9, 0.99, 0.999];
    let mut points = Vec::new();
    for &x in &xs {
        points.push(PointCase {
            case_id: format!("x{x}"),
            x,
        });
    }
    let mut ppf_cases = Vec::new();
    for &q in &qs {
        ppf_cases.push(PpfCase {
            case_id: format!("q{q}"),
            q,
        });
    }
    OracleQuery {
        points,
        ppf: ppf_cases,
    }
}

fn scipy_oracle_or_skip(query: &OracleQuery) -> Option<OracleResult> {
    let script = r#"
import json
import sys
from scipy.stats import halfnorm

q = json.load(sys.stdin)
points = []
for case in q["points"]:
    cid = case["case_id"]
    x = float(case["x"])
    try:
        points.append({
            "case_id": cid,
            "pdf": float(halfnorm.pdf(x, 0.0, 1.0)),
            "cdf": float(halfnorm.cdf(x, 0.0, 1.0)),
            "sf":  float(halfnorm.sf(x, 0.0, 1.0)),
        })
    except Exception:
        points.append({"case_id": cid, "pdf": None, "cdf": None, "sf": None})
ppf = []
for case in q["ppf"]:
    cid = case["case_id"]; qv = float(case["q"])
    try:
        ppf.append({"case_id": cid, "ppf": float(halfnorm.ppf(qv, 0.0, 1.0))})
    except Exception:
        ppf.append({"case_id": cid, "ppf": None})
print(json.dumps({"points": points, "ppf": ppf}))
"#;

    let query_json = serde_json::to_string(query).expect("serialize halfnorm query");
    let mut child = match fsci_conformance::scipy_oracle_command()
        .arg("-c")
        .arg(script)
        .stdin(Stdio::piped())
        .stdout(Stdio::piped())
        .stderr(Stdio::piped())
        .spawn()
    {
        Ok(c) => c,
        Err(e) => {
            assert!(
                std::env::var(REQUIRE_SCIPY_ENV).is_err(),
                "failed to spawn python3 for halfnorm oracle: {e}"
            );
            eprintln!("skipping halfnorm oracle: python3 not available ({e})");
            return None;
        }
    };
    {
        let stdin = child.stdin.as_mut().expect("open halfnorm oracle stdin");
        if let Err(err) = stdin.write_all(query_json.as_bytes()) {
            let output = child.wait_with_output().expect("wait for failed oracle");
            let stderr = String::from_utf8_lossy(&output.stderr);
            assert!(
                std::env::var(REQUIRE_SCIPY_ENV).is_err(),
                "halfnorm oracle stdin write failed: {err}; stderr: {stderr}"
            );
            eprintln!("skipping halfnorm oracle: stdin write failed ({err})\n{stderr}");
            return None;
        }
    }
    let output = child.wait_with_output().expect("wait for halfnorm oracle");
    if !output.status.success() {
        let stderr = String::from_utf8_lossy(&output.stderr);
        assert!(
            std::env::var(REQUIRE_SCIPY_ENV).is_err(),
            "halfnorm oracle failed: {stderr}"
        );
        eprintln!("skipping halfnorm oracle: scipy not available\n{stderr}");
        return None;
    }
    let stdout = String::from_utf8_lossy(&output.stdout);
    Some(serde_json::from_str(&stdout).expect("parse halfnorm oracle JSON"))
}

#[test]
fn diff_stats_halfnorm() {
    let query = generate_query();
    let Some(oracle) = scipy_oracle_or_skip(&query) else {
        return;
    };
    assert_eq!(oracle.points.len(), query.points.len());
    assert_eq!(oracle.ppf.len(), query.ppf.len());

    let pmap: HashMap<String, PointArm> = oracle
        .points
        .into_iter()
        .map(|r| (r.case_id.clone(), r))
        .collect();
    let ppfmap: HashMap<String, PpfArm> = oracle
        .ppf
        .into_iter()
        .map(|r| (r.case_id.clone(), r))
        .collect();

    let start = Instant::now();
    let mut diffs = Vec::new();
    let mut max_overall = 0.0_f64;
    let dist = HalfNormal;
    let mut ledger = CompareLedger::new("diff_stats_halfnorm", &["pdf", "cdf", "sf", "ppf"]);

    for case in &query.points {
        let oracle = pmap.get(&case.case_id).expect("validated oracle");
        let arms = [
            ("pdf", oracle.pdf, dist.pdf(case.x), PDF_TOL),
            ("cdf", oracle.cdf, dist.cdf(case.x), CDF_TOL),
            ("sf", oracle.sf, dist.sf(case.x), SF_TOL),
        ];
        for (family, scipy, fsci, tol) in arms {
            let Some((s, f)) = ledger.pair(family, &case.case_id, scipy, Some(fsci)) else {
                continue;
            };
            let d = (f - s).abs();
            max_overall = max_overall.max(d);
            ledger.compared(family, &case.case_id, d <= tol);
            diffs.push(CaseDiff {
                case_id: case.case_id.clone(),
                family: family.into(),
                abs_diff: d,
                pass: d <= tol,
            });
        }
    }

    for case in &query.ppf {
        let oracle = ppfmap.get(&case.case_id).expect("validated oracle");
        let Some((sppf, rust)) =
            ledger.pair("ppf", &case.case_id, oracle.ppf, Some(dist.ppf(case.q)))
        else {
            continue;
        };
        let d = (rust - sppf).abs();
        let scale = sppf.abs().max(1.0);
        max_overall = max_overall.max(d);
        ledger.compared("ppf", &case.case_id, d <= PPF_TOL_REL * scale);
        diffs.push(CaseDiff {
            case_id: case.case_id.clone(),
            family: "ppf".into(),
            abs_diff: d,
            pass: d <= PPF_TOL_REL * scale,
        });
    }

    let all_pass = diffs.iter().all(|d| d.pass);

    let log = DiffLog {
        test_id: "diff_stats_halfnorm".into(),
        category: "scipy.stats.halfnorm".into(),
        case_count: diffs.len(),
        compared: ledger.counts().clone(),
        max_abs_diff: max_overall,
        pass: all_pass,
        timestamp_ms: timestamp_ms(),
        duration_ns: start.elapsed().as_nanos(),
        cases: diffs.clone(),
    };

    emit_log(&log);

    for d in &diffs {
        if !d.pass {
            eprintln!(
                "halfnorm {} mismatch: {} abs_diff={}",
                d.family, d.case_id, d.abs_diff
            );
        }
    }

    assert!(
        all_pass,
        "scipy.stats.halfnorm conformance failed: {} cases, max_diff={}",
        diffs.len(),
        max_overall
    );
    // pdf/cdf/sf compare every x point; ppf has its own (smaller) q-grid.
    ledger.finish(query.points.len().min(query.ppf.len()));
}