C++ segmentation fault when creating aligned struct data twice

Question

I am trying to write some c++ code which is crucial for performance. Therefor I am using AVX intrinsics and need to align my data to 32 byte.

I am using a struct which look similar to this: (I commented out parts of it to track down the issue)

struct Summation {
    alignas(ALIGNMENT) float summation[HIDDEN_SIZE] {};

    Summation() {
//        std::memcpy(summation, inputBias, sizeof(float) * HIDDEN_SIZE);
    }

    Summation& operator=(const Summation& other) {
//        std::memcpy(summation, other.summation, sizeof(float) * HIDDEN_SIZE);
        return *this;
    }
};



struct Evaluator {

    Evaluator(){}

    // inputs and outputs
    bool inputMap[INPUT_SIZE] {};
    
    // bias
    alignas(32) float input_bias[HIDDEN_SIZE] {};
    alignas(32) float hidden_bias {};
    
    // weights
    alignas(32) float input_weights[INPUT_SIZE][HIDDEN_SIZE] {};
    alignas(32) float hidden_weights[HIDDEN_SIZE] {};

    alignas(32) float activation[HIDDEN_SIZE] {};

    std::vector<Summation> summations {};

Compiling this works with no issues and running the following works without any problems:

    nn::Evaluator ev1{};

The issue arises when I try to create a second Evaluator:

    nn::Evaluator ev1{};
    nn::Evaluator ev2{};


--> 
Process finished with exit code -1073741571 (0xC00000FD)

I tracked down the problem to the creation of

alignas(32) float input_weights[INPUT_SIZE][HIDDEN_SIZE] {};

Yet I do not know why this would cause problems when creating a second Evaluator object but works with only a single Evaluator. I am very happy for any help.

Answer 1

I have found the issue already. It turns out its not the alignment but the allocation on the stack. Since the 2d-array is very large compared to the other data contained, it allocates too much memory on the stack and causes a stackoverflow.