# This function the most simple manual way of doing matrix multiplication without builtins
# It does not take into account multithreading or any acceleration
# It does however use the least amount of memory, only allocating new memory for the sum and the results matrix
function for_loop(a, b)
    n = size(a, 1)
    m = size(b, 1)
    if (size(a, 2) != m)
        println("Matrixes not of multipliable sizes")
    end
    p = size(b, 2)
    
    c = Matrix{Int}(undef, n, p)

    for i in 1:n
        for j in 1:p
            sum = 0
            for k in 1:m
                a1 = a[i, k]
                b1 = b[k, j]
                sum = sum + (a1 * b1)
            end
            c[i, j] = sum
        end
    end
    c
end

# This function is very easy as a programmer to use, as it is builtin and uses OpenBLAS, which has more advanced algorithms for doing matrix multiplication
# However, it fails under a few scenarios, where you are memory bound doing a lot of multiplications on low dimension matrixes
# as it uses much more memory even for a simple 5x5 matrix than the for loop, presumably due to allocation costs and setup/error checking
function built_in(a, b)
    a * b
end

# In terms of speed, the for loop loses in pretty much every scenario, but wins initially in terms of memory usage, but as the
# matrixes begin to scale dimensions into hundreds or thousands, the builtin becomes much closer in terms of memory usage
function main()
    matrix_regex = r"(\d+)x(\d+)"

    println("Format is {num}x{num}. Eg: 3x3 or 100x100")

    print("Dimension of first matrix: ")
    input = readline()
    matrix_match = match(matrix_regex, input)
    matrix_1 = rand(Int, (parse(Int, matrix_match[1]), parse(Int, matrix_match[2])))

    print("Dimension of second matrix: ")
    input = readline()
    matrix_match = match(matrix_regex, input)
    matrix_2 = rand(Int, (parse(Int, matrix_match[1]), parse(Int, matrix_match[2])))

    println("For loop")
    @time for_loop(matrix_1, matrix_2)

    println("Builtin")
    @time built_in(matrix_1, matrix_2)
end

main()