java-topology/defects/cmake-0007/unit/DllDirsAlgorithm.java

import java.util.*;

/**
 * Unit test for cmake-0007: TargetRuntimeDllDirsNode O(D^2) -> O(D) dedup.
 *
 * Models $<TARGET_RUNTIME_DLL_DIRS:tgt> evaluator: collect unique DLL directories
 * from a list of DLL paths, preserving insertion order.
 *
 * Defect: std::find over growing dllDirs vector = O(D) per entry = O(D^2) total.
 * Fix:    parallel unordered_set for membership + vector for order = O(1) per entry.
 */
public class DllDirsAlgorithm {

    static String getFilenamePath(String path) {
        int slash = Math.max(path.lastIndexOf('/'), path.lastIndexOf('\\'));
        return slash >= 0 ? path.substring(0, slash) : ".";
    }

    // --- Defective: O(D^2) ---
    static List<String> collectDllDirsDefective(List<String> dlls) {
        List<String> dllDirs = new ArrayList<>();
        for (String dll : dlls) {
            String dir = getFilenamePath(dll);
            if (!dllDirs.contains(dir)) { // O(D) linear scan -- the defect
                dllDirs.add(dir);
            }
        }
        return dllDirs;
    }

    // --- Fixed: O(D) ---
    static List<String> collectDllDirsFixed(List<String> dlls) {
        List<String> dllDirs = new ArrayList<>();
        Set<String> dllDirsSet = new HashSet<>();
        for (String dll : dlls) {
            String dir = getFilenamePath(dll);
            if (dllDirsSet.add(dir)) { // O(1) hash insert+check
                dllDirs.add(dir);
            }
        }
        return dllDirs;
    }

    static List<String> makeDlls(int numDirs, int dllsPerDir) {
        List<String> dlls = new ArrayList<>();
        for (int d = 0; d < numDirs; d++) {
            for (int i = 0; i < dllsPerDir; i++) {
                dlls.add("C:/Qt/" + d + "/lib" + i + ".dll");
            }
        }
        return dlls;
    }

    static void testCorrectness() {
        List<String> dlls = Arrays.asList(
            "C:/Qt/bin/Qt6Core.dll",
            "C:/Qt/bin/Qt6Gui.dll",
            "C:/Boost/lib/boost_system.dll",
            "C:/Qt/bin/Qt6Widgets.dll",
            "C:/Boost/lib/boost_thread.dll"
        );

        List<String> defect = collectDllDirsDefective(dlls);
        List<String> fixed = collectDllDirsFixed(dlls);

        if (!defect.equals(fixed)) {
            throw new AssertionError("Results differ: " + defect + " vs " + fixed);
        }
        if (defect.size() != 2) {
            throw new AssertionError("Expected 2 unique dirs, got " + defect.size() + ": " + defect);
        }
        // Order must be preserved (insertion order)
        if (!defect.get(0).equals("C:/Qt/bin") || !defect.get(1).equals("C:/Boost/lib")) {
            throw new AssertionError("Wrong order: " + defect);
        }
        System.out.println("PASS testCorrectness (2 unique dirs, insertion order preserved)");
    }

    static void testAllUnique() {
        List<String> dlls = Arrays.asList(
            "C:/dir1/a.dll", "C:/dir2/b.dll", "C:/dir3/c.dll"
        );
        List<String> result = collectDllDirsFixed(dlls);
        if (result.size() != 3) throw new AssertionError("Expected 3: " + result);
        System.out.println("PASS testAllUnique");
    }

    static void testAllSameDir() {
        List<String> dlls = Arrays.asList(
            "C:/Qt/bin/A.dll", "C:/Qt/bin/B.dll", "C:/Qt/bin/C.dll"
        );
        List<String> result = collectDllDirsFixed(dlls);
        if (result.size() != 1) throw new AssertionError("Expected 1: " + result);
        if (!result.get(0).equals("C:/Qt/bin")) throw new AssertionError("Wrong dir: " + result);
        System.out.println("PASS testAllSameDir");
    }

    static void testBenchmark() {
        int NUM_DIRS = 20;
        int DLLS_PER_DIR = 5; // 100 DLLs total, 20 unique dirs
        List<String> dlls = makeDlls(NUM_DIRS, DLLS_PER_DIR);
        int D = dlls.size();

        // Count defective ops (linear scans in contains)
        long defectiveOps = 0;
        List<String> seen = new ArrayList<>();
        for (String dll : dlls) {
            String dir = getFilenamePath(dll);
            for (String s : seen) { defectiveOps++; if (s.equals(dir)) break; }
            if (!seen.contains(dir)) seen.add(dir);
        }

        long fixedOps = D; // one hash lookup per dll
        double ratio = (double) defectiveOps / fixedOps;
        System.out.printf("BENCH dllDirs D=%d dirs=%d: defective=%d ops, fixed=%d ops, ratio=%.1fx%n",
            D, NUM_DIRS, defectiveOps, fixedOps, ratio);
        if (ratio < 2.0) {
            throw new AssertionError("Expected ratio >= 2x, got " + ratio);
        }
        System.out.println("PASS testBenchmark (ratio >= 2x confirmed)");
    }

    public static void main(String[] args) {
        testCorrectness();
        testAllUnique();
        testAllSameDir();
        testBenchmark();
        System.out.println("ALL PASS cmake-0007 DllDirs");
    }
}