Segmentation Fault with Large Matrix Dimensions

[FilippoTib]

Segmentation Fault with Large Matrix Dimensions

Hello everyone,
I encountered a segmentation fault when using the provided example code with large matrix dimensions.

Description

When initializing a sparse matrix with non-trivial dimensions (e.g., the size of the com-Orkut dataset), the program crashes with a segmentation fault during matrix construction.

Example Code

#include <iostream>
#include "IVSparse/SparseMatrix"

int main() {
    std::vector<std::tuple<uint32_t, uint32_t, double>> cooData = {
        {0, 0, 1},
        {1, 1, 2},
        {2, 2, 3},
        {3, 3, 4}
    };

    int rows = 3072441; // com-Orkut dataset size
    int cols = 3072441; // Causes segmentation fault

//  int rows = 46985;   // Web of Science dataset size
//  int cols = 124836; // Works correctly

    int nnz = 4;

    IVSparse::SparseMatrix<double> matrix(cooData, rows, cols, nnz);

    std::cout << "Everything ok!\n";
    return 0;
}

Observed Behavior

• The program runs correctly with smaller matrix sizes.
• With large dimensions (e.g., ~3 million × 3 million), it crashes with a segmentation fault during construction.

Suspected Cause

I suspect that the issue may be caused by large stack allocations using Variable Length Arrays (VLAs), such as:

std::map<T2, std::vector<indexT2>> maps[outerDim];

Located in: IVSparse/src/IVCSC/IVCSC_Constructors.hpp (around line 309)

Proposed Solution

Replace stack-allocated VLAs with heap-allocated containers.

Suggested Change

// Original
std::map<T2, std::vector<indexT2>> maps[outerDim];

// Modified
std::vector<std::map<T2, std::vector<indexT2>>> maps(outerDim);

This shifts the allocation to the heap and avoids stack overflow.

Steps to Reproduce

1. Clone the repository.

2. Create a file named new_test_ft.cpp in the root directory and paste the example code above.

3. Compile using:

   g++ -std=c++17 -fopenmp -O2 new_test_ft.cpp -I. -I/usr/include/eigen3 -o test

4. Run:

   ./test

Environment

• OS
  Distributor ID: Ubuntu
  Description: Ubuntu 24.04.3 LTS
  Release: 24.04
  Codename: noble

• Compiler
  g++ --version -> g++ (Ubuntu 13.3.0-6ubuntu2~24.04.1) 13.3.0

• Arch
  uname -m -> x86_64

• Stack size
  ulimit -s -> 8192

• Available RAM
  total used free shared buff/cache available
  Mem: 7.6Gi 1.7Gi 625Mi 28Mi 5.6Gi 5.9Gi
  Swap: 8.0Gi 12Mi 8.0Gi

---

Please let me know if additional details or tests would be helpful. I’d be happy to assist further in debugging this issue.