Fix assertion bugs in LDLTDecomposition.h

[CodeReclaimers]

Summary

• Solve(): D.GetNumCols() was missing == N comparison, always passing for any nonzero column count
• Block LDLT Convert(): block matrix size validated against NumBlocks instead of BlockSize

Test plan

Test passes wrong-sized inputs and verifies the assertions fire. Both tests FAIL before the fix and PASS after.

Test code (click to expand)

#include <Mathematics/LDLTDecomposition.h>
#include <cstdlib>
#include <iostream>
#include <stdexcept>

using namespace gte;

bool test_issue_7_2()
{
    LDLTDecomposition<double> decomp(3);

    GMatrix<double> A(3, 3);
    A.MakeZero();
    A(0, 0) = 4.0;
    A(1, 1) = 5.0;
    A(2, 2) = 6.0;

    GMatrix<double> L, D;
    decomp.Factor(A, L, D);

    // D with MORE columns than expected (5 instead of 3).
    // Using more columns so D(r,r) for r=0..2 are valid accesses,
    // isolating the assertion bug from any later out-of-bounds access.
    GMatrix<double> D_wrong(3, 5);
    D_wrong.MakeZero();
    D_wrong(0, 0) = 4.0;
    D_wrong(1, 1) = 5.0;
    D_wrong(2, 2) = 6.0;

    GVector<double> B(3);
    B[0] = 1.0; B[1] = 2.0; B[2] = 3.0;
    GVector<double> X;

    // Before fix: D.GetNumCols() evaluates as bool(5) = true, passes.
    // After fix:  D.GetNumCols() == N evaluates as (5 == 3) = false, throws.
    try
    {
        decomp.Solve(L, D_wrong, B, X);
        std::cerr << "FAIL 7.2: accepted D with wrong column count" << std::endl;
        return false;
    }
    catch (std::runtime_error&)
    {
        std::cout << "PASS 7.2" << std::endl;
        return true;
    }
}

bool test_issue_7_3()
{
    // BlockSize=2, NumBlocks=3 (they differ).
    BlockLDLTDecomposition<double> decomp(2, 3);

    // Blocks of WRONG size: 3x3 (== NumBlocks) instead of 2x2 (== BlockSize).
    BlockLDLTDecomposition<double>::BlockMatrix wrongBlocks(9);
    for (auto& block : wrongBlocks)
    {
        block.SetSize(3, 3);
        block.MakeZero();
    }

    GMatrix<double> M;

    // Before fix: validates rows == NumBlocks (3 == 3), passes.
    // After fix:  validates rows == BlockSize (3 == 2), throws.
    try
    {
        decomp.Convert(wrongBlocks, M);
        std::cerr << "FAIL 7.3: accepted blocks with wrong dimensions" << std::endl;
        return false;
    }
    catch (std::runtime_error&)
    {
        std::cout << "PASS 7.3" << std::endl;
        return true;
    }
}

int main()
{
    bool pass = true;
    pass = test_issue_7_2() && pass;
    pass = test_issue_7_3() && pass;
    return pass ? EXIT_SUCCESS : EXIT_FAILURE;
}

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