java-topology/defects/julia/unit/JuliaTest.java

package unit;

import java.util.*;

/**
 * JuliaTest — CWE-407 benchmark for julia-0001
 *
 * Models isrelocatable() O(N²) Vector membership test in includes loop
 * vs. O(N) HashSet-based check.
 *
 * Real code (base/loading.jl ~2102):
 *   for inc in includes                          # outer O(n)
 *       if inc ∉ includes_srcfiles               # inner O(n) Vector linear scan
 *
 * Fix: srcfiles_set = Set{CacheHeaderIncludes}(includes_srcfiles) → O(1) lookup.
 */
public class JuliaTest {

    static void bench(String label, Runnable slow, Runnable fast, long sOps, long fOps) {
        slow.run(); fast.run();
        long t0 = System.nanoTime(); slow.run(); long sMs = (System.nanoTime() - t0) / 1_000_000;
        long t1 = System.nanoTime(); fast.run(); long fMs = (System.nanoTime() - t1) / 1_000_000;
        double speedup = fMs > 0 ? (double) sMs / fMs : 0;
        System.out.printf("  %-54s  slow:%4dms (%,d ops)  fast:%4dms (%,d ops)  speedup:%.0fx%n",
                label, sMs, sOps, fMs, fOps, speedup);
    }

    static long slowIsRelocatable(int N) {
        List<Integer> includes = new ArrayList<>(N);
        List<Integer> srcfiles = new ArrayList<>(N / 2);
        for (int i = 0; i < N; i++) includes.add(i);
        for (int i = 0; i < N / 2; i++) srcfiles.add(i * 2);
        long ops = 0;
        for (Integer inc : includes) {
            for (Integer sf : srcfiles) {
                ops++;
                if (sf.equals(inc)) break;
            }
        }
        return ops;
    }

    static long fastIsRelocatable(int N) {
        List<Integer> includes = new ArrayList<>(N);
        Set<Integer> srcfileSet = new HashSet<>(N);
        for (int i = 0; i < N; i++) includes.add(i);
        for (int i = 0; i < N / 2; i++) srcfileSet.add(i * 2);
        long ops = 0;
        for (Integer inc : includes) {
            ops++;
            srcfileSet.contains(inc);
        }
        return ops;
    }

    public static void main(String[] args) {
        System.out.println("JuliaTest -- julia-0001: isrelocatable() includes_srcfiles Vector scan -> HashSet");
        System.out.println();
        System.out.println("  [isrelocatable-includes: base/loading.jl ~2102]");
        int[][] cases = {{200, 10000}, {500, 5000}, {1000, 2000}};
        for (int[] c : cases) {
            int N = c[0], R = c[1];
            bench(
                String.format("N=%d includes, %,d isrelocatable() calls", N, R),
                () -> { for (int i = 0; i < R; i++) slowIsRelocatable(N); },
                () -> { for (int i = 0; i < R; i++) fastIsRelocatable(N); },
                (long) N * (N / 2) * R,
                (long) N * R
            );
        }
        System.out.println();
        System.out.println("Defect : base/loading.jl ~2102 -- 'inc not in includes_srcfiles' Vector O(n) scan");
        System.out.println("Fix    : srcfiles_set = Set{CacheHeaderIncludes}(includes_srcfiles) -- O(1) check");
        System.out.println("Ticket : julia-0001-isrelocatable-includes-vector-linear-scan.md");
        System.out.println();
        int pass = 0;
        long s0 = slowIsRelocatable(1000), f0 = fastIsRelocatable(1000);
        assert s0 > f0 * 50 : "julia-0001 expected >50x; slow=" + s0 + " fast=" + f0; pass++;
        System.out.printf("%d/1 PASS -- julia-0001: CWE-407 in Julia isrelocatable() package validation%n", pass);
        System.out.printf("Hotpath: called for every package during precompile validation%n");
    }
}