java-topology/tests/unit/FindNodeComplexityTest.java

package unit;

import support.FindNodeAlgorithm;
import support.FindNodeAlgorithm.Result;

/**
 * Unit tests for DEFECT 0002a: InferenceGraph.findNode() O(N) ArrayList scan.
 *
 * Proves:
 *   1. Both implementations find the same nodes (correctness).
 *   2. Defective version makes exactly N*(N+1)/2 comparisons for N queries.
 *   3. Fixed version makes exactly N comparisons for N queries.
 *   4. Doubling N quadruples defective work; doubling N doubles fixed work.
 *
 * No build tool required. Compile and run:
 *
 *   cd tests
 *   java -m jdk.compiler/com.sun.tools.javac.Main -cp . \
 *        support/FindNodeAlgorithm.java unit/FindNodeComplexityTest.java
 *   java -cp . unit.FindNodeComplexityTest
 */
public class FindNodeComplexityTest {

    private static int passed = 0;
    private static int failed = 0;

    public static void main(String[] args) {
        System.out.println("=== FindNodeComplexityTest (DEFECT 0002a) ===\n");

        System.out.println("-- Correctness: both finders return same nodes --");
        testCorrectnessSmall();
        testCorrectnessMedium();
        testAllFound();

        System.out.println("\n-- Complexity: defective comparison counts N*(N+1)/2 --");
        testDefectiveExactCounts();

        System.out.println("\n-- Complexity: fixed comparison counts N --");
        testFixedExactCounts();

        System.out.println("\n-- Complexity: growth ratio proves quadratic vs linear --");
        testGrowthRatio();

        System.out.printf("\n%d passed, %d failed%n", passed, failed);
        if (failed > 0) System.exit(1);
    }

    // ─── Correctness ─────────────────────────────────────────────────────────

    static void testCorrectnessSmall() {
        Result def = FindNodeAlgorithm.queryAllDefective(5);
        Result fix = FindNodeAlgorithm.queryAllFixed(5);
        assertEqual("small: defective found count", 5, def.found.size());
        assertEqual("small: fixed found count",     5, fix.found.size());
        for (int i = 0; i < 5; i++) {
            assertTrue("small: defective found[" + i + "] not null", def.found.get(i) != null);
            assertTrue("small: fixed found[" + i + "] not null",     fix.found.get(i) != null);
            assertEqual("small: defective found[" + i + "] label",
                    "N" + i, def.found.get(i).label);
            assertEqual("small: fixed found[" + i + "] label",
                    "N" + i, fix.found.get(i).label);
        }
    }

    static void testCorrectnessMedium() {
        Result def = FindNodeAlgorithm.queryAllDefective(20);
        Result fix = FindNodeAlgorithm.queryAllFixed(20);
        assertEqual("medium: defective found count", 20, def.found.size());
        assertEqual("medium: fixed found count",     20, fix.found.size());
        for (int i = 0; i < 20; i++) {
            assertEqual("medium: found[" + i + "] labels match",
                    def.found.get(i).label, fix.found.get(i).label);
        }
    }

    static void testAllFound() {
        // No null results — every query hits
        Result def = FindNodeAlgorithm.queryAllDefective(10);
        long nullCount = def.found.stream().filter(n -> n == null).count();
        assertEqual("all-found: no nulls in defective", 0L, nullCount);

        Result fix = FindNodeAlgorithm.queryAllFixed(10);
        long nullCountFix = fix.found.stream().filter(n -> n == null).count();
        assertEqual("all-found: no nulls in fixed", 0L, nullCountFix);
    }

    // ─── Exact comparison counts ──────────────────────────────────────────────

    /**
     * PROVES DEFECT: querying all N nodes in order 0..N-1 forces exactly
     * N*(N+1)/2 element comparisons with the ArrayList scan.
     *
     * Derivation: query N0 finds it at index 0 (1 comparison), N1 found at
     * index 1 (2 comparisons), ..., N(k) found at index k (k+1 comparisons).
     * Total: sum(k+1, k=0..N-1) = N*(N+1)/2.
     */
    static void testDefectiveExactCounts() {
        System.out.println("[defective] queryAll(N) — expected N*(N+1)/2:");
        int[] sizes = {5, 10, 20, 50, 100};
        for (int n : sizes) {
            Result r = FindNodeAlgorithm.queryAllDefective(n);
            long expected = (long) n * (n + 1) / 2;
            System.out.printf("  N=%-4d  actual=%-8d  expected=%-8d  %s%n",
                    n, r.comparisons, expected,
                    r.comparisons == expected ? "PASS" : "FAIL expected=" + expected);
            assertEqual("defective N=" + n, expected, r.comparisons);
        }
    }

    /**
     * PROVES FIX: N queries against a HashMap require exactly N comparisons — one per lookup.
     */
    static void testFixedExactCounts() {
        System.out.println("[fixed] queryAll(N) — expected N:");
        int[] sizes = {5, 10, 20, 50, 100};
        for (int n : sizes) {
            Result r = FindNodeAlgorithm.queryAllFixed(n);
            long expected = n;
            System.out.printf("  N=%-4d  actual=%-8d  expected=%-8d  %s%n",
                    n, r.comparisons, expected,
                    r.comparisons == expected ? "PASS" : "FAIL");
            assertEqual("fixed N=" + n, expected, r.comparisons);
        }
    }

    // ─── Growth ratio ─────────────────────────────────────────────────────────

    /**
     * PROVES QUADRATIC GROWTH of defect:
     * Doubling N → defective comparisons quadruple (≈4x), fixed double (≈2x).
     *
     * Math:
     *   defective(N)   = N*(N+1)/2 ≈ N²/2
     *   defective(2N)  = 2N*(2N+1)/2 ≈ 2N²  → ratio ≈ 4
     *   fixed(N)  = N,  fixed(2N) = 2N         → ratio = 2 (exact)
     */
    static void testGrowthRatio() {
        int[][] pairs = {{10, 20}, {20, 40}, {50, 100}, {100, 200}};
        for (int[] pair : pairs) {
            int n1 = pair[0], n2 = pair[1];

            long def1 = FindNodeAlgorithm.queryAllDefective(n1).comparisons;
            long def2 = FindNodeAlgorithm.queryAllDefective(n2).comparisons;
            long fix1 = FindNodeAlgorithm.queryAllFixed(n1).comparisons;
            long fix2 = FindNodeAlgorithm.queryAllFixed(n2).comparisons;

            double defRatio = (double) def2 / def1;
            double fixRatio = (double) fix2 / fix1;

            System.out.printf("  N %d→%d:  defective ratio=%.2f (expect ~4.0)  fixed ratio=%.2f (expect 2.0)%n",
                    n1, n2, defRatio, fixRatio);

            assertTrue("defective N=" + n1 + "→" + n2 + " ratio ≥ 3.8", defRatio >= 3.8);
            assertTrue("defective N=" + n1 + "→" + n2 + " ratio ≤ 4.2", defRatio <= 4.2);
            assertTrue("fixed N=" + n1 + "→" + n2 + " ratio = 2.0",     fixRatio == 2.0);
        }
    }

    // ─── Helpers ─────────────────────────────────────────────────────────────

    static void assertEqual(String name, long expected, long actual) {
        if (expected == actual) {
            System.out.printf("  PASS  %s%n", name);
            passed++;
        } else {
            System.out.printf("  FAIL  %s  expected=%d  actual=%d%n", name, expected, actual);
            failed++;
        }
    }

    static void assertEqual(String name, String expected, String actual) {
        if (expected.equals(actual)) {
            System.out.printf("  PASS  %s%n", name);
            passed++;
        } else {
            System.out.printf("  FAIL  %s  expected=%s  actual=%s%n", name, expected, actual);
            failed++;
        }
    }

    static void assertTrue(String name, boolean condition) {
        if (condition) {
            System.out.printf("  PASS  %s%n", name);
            passed++;
        } else {
            System.out.printf("  FAIL  %s%n", name);
            failed++;
        }
    }
}