java-topology/defects/ogre/unit/OgreTest.java

import java.util.*;

/**
 * CWE-407 simulation: OGRE3D GLSLProgramWriter inParams linear scan.
 *
 * Defect: ogre-0001
 * File:   Components/RTShaderSystem/src/OgreShaderGLSLProgramWriter.cpp
 *
 * In writeSourceCode(), for every function invocation atom and for every
 * operand within that atom, the code calls:
 *
 *   std::find(inParams.begin(), inParams.end(), param)
 *
 * where inParams is a vector<ParameterPtr>. This is O(P) per operand, giving
 * overall O(A * O * P) where:
 *   A = atom instances (function invocations)
 *   O = operands per atom
 *   P = number of input parameters
 *
 * Fix: build an unordered_set<const Parameter*> from inParams before the loop,
 * reducing the per-operand lookup to O(1) → overall O(A * O).
 */
public class OgreTest {

    /**
     * Simulates the defective O(A*O*P) inParams lookup:
     * for each atom, for each operand, do a linear scan of inParams.
     *
     * @param numAtoms     number of function invocation atoms (A)
     * @param numOperands  operands per atom (O)
     * @param numInParams  number of input parameters (P)
     * @return total comparison operations performed
     */
    static long defectiveShaderWrite(int numAtoms, int numOperands, int numInParams) {
        // Simulate inParams as a list of IDs
        List<Integer> inParams = new ArrayList<>(numInParams);
        for (int i = 0; i < numInParams; i++) {
            inParams.add(i);
        }

        long ops = 0;
        for (int a = 0; a < numAtoms; a++) {
            for (int o = 0; o < numOperands; o++) {
                // The operand parameter ID — picks half from inParams, half not
                int paramId = (a * numOperands + o) % (numInParams * 2);
                // std::find: O(P) scan
                boolean found = false;
                for (int p = 0; p < numInParams; p++) {
                    ops++;
                    if (inParams.get(p).equals(paramId)) {
                        found = true;
                        break;
                    }
                }
            }
        }
        return ops;
    }

    /**
     * Simulates the fixed O(A*O) inParams lookup using a hash set.
     *
     * @param numAtoms     number of function invocation atoms (A)
     * @param numOperands  operands per atom (O)
     * @param numInParams  number of input parameters (P)
     * @return total comparison operations performed
     */
    static long fixedShaderWrite(int numAtoms, int numOperands, int numInParams) {
        Set<Integer> inParamSet = new HashSet<>(numInParams);
        for (int i = 0; i < numInParams; i++) {
            inParamSet.add(i);
        }

        long ops = 0;
        for (int a = 0; a < numAtoms; a++) {
            for (int o = 0; o < numOperands; o++) {
                int paramId = (a * numOperands + o) % (numInParams * 2);
                ops++; // hash-set lookup is O(1)
                boolean found = inParamSet.contains(paramId);
            }
        }
        return ops;
    }

    public static void main(String[] args) {
        // --- Correctness test: both must agree on which params are "input params" ---
        int P = 10, A = 5, O = 4;
        List<Integer> inParams = new ArrayList<>();
        for (int i = 0; i < P; i++) inParams.add(i);
        Set<Integer> inParamSet = new HashSet<>(inParams);

        List<Boolean> defectResults = new ArrayList<>();
        List<Boolean> fixedResults  = new ArrayList<>();
        for (int a = 0; a < A; a++) {
            for (int o = 0; o < O; o++) {
                int paramId = (a * O + o) % (P * 2);
                defectResults.add(inParams.contains(paramId));
                fixedResults.add(inParamSet.contains(paramId));
            }
        }
        assert defectResults.equals(fixedResults)
            : "Correctness check failed: defective and fixed produce different results";
        System.out.println("PASS: correctness verified for inParams membership lookup");

        // --- Op-count ratio test ---
        System.out.println("\nOperation count ratio (defective / fixed):");
        int[][] configs = {
            {50, 8, 20},
            {100, 10, 50},
            {200, 12, 100},
        };
        for (int[] cfg : configs) {
            int atoms = cfg[0], operands = cfg[1], params = cfg[2];
            long dOps = defectiveShaderWrite(atoms, operands, params);
            long fOps = fixedShaderWrite(atoms, operands, params);
            double ratio = (double) dOps / fOps;
            System.out.printf("  A=%3d O=%2d P=%3d  defect=%7d  fixed=%5d  ratio=%.1fx%n",
                              atoms, operands, params, dOps, fOps, ratio);
            assert ratio > 2.0
                : "Expected ratio > 2x, got " + ratio + " for A=" + atoms + " O=" + operands + " P=" + params;
        }

        // --- Wall-clock timing ---
        int bigA = 400, bigO = 20, bigP = 200;
        long t0 = System.nanoTime();
        defectiveShaderWrite(bigA, bigO, bigP);
        long defectNs = System.nanoTime() - t0;

        t0 = System.nanoTime();
        fixedShaderWrite(bigA, bigO, bigP);
        long fixedNs = System.nanoTime() - t0;

        double wallRatio = (double) defectNs / Math.max(fixedNs, 1);
        System.out.printf("%nWall-clock timing for A=%d O=%d P=%d:%n", bigA, bigO, bigP);
        System.out.printf("  defective: %6.2f ms%n", defectNs / 1e6);
        System.out.printf("  fixed:     %6.2f ms%n", fixedNs / 1e6);
        System.out.printf("  ratio:     %.1fx%n", wallRatio);

        assert wallRatio > 1.5
            : "Expected wall-clock ratio > 1.5x, got " + wallRatio;

        System.out.println("\nPASS: all assertions passed");
    }
}