     // free memory on device
     cudaFree(d_src_data);
     cudaFree(d_dst_data);
-    cudaFree(d_pixel_equ);
+    // cudaFree(d_pixel_equ);
     cudaFree(d_block_equ);
     cudaFree(d_grid_equ);
 

    do {
        // 2D grid & 2D block
        skeletonize_pass<<<grid_dim, block_dim>>>(d_src_data, d_dst_data, (*src_bitmap)->width, padding);
        pixel_equality<<<grid_dim, block_dim>>>(d_src_data, d_dst_data, d_pixel_equ, (*src_bitmap)->width, padding);

        // 1D grid & 1D block reduction
        and_reduction(grid_dim, block_dim, d_pixel_equ, d_block_equ, d_grid_equ, pixel_equ_size, block_equ_size);

        // bring d_grid_equ back from device
        cudaMemcpy(&grid_equ, d_grid_equ, grid_equ_size, cudaMemcpyDeviceToHost);

    // allocate memory on device
    uint8_t* d_src_data = NULL;
    uint8_t* d_dst_data = NULL;
    // uint8_t* d_pixel_equ = NULL;
    uint8_t* d_block_equ = NULL;
    uint8_t* d_grid_equ = NULL;

    unsigned int data_size = (*src_bitmap)->width * (*src_bitmap)->height * sizeof(uint8_t);
    // unsigned int pixel_equ_size = ((*src_bitmap)->width - padding.left - padding.right) * ((*src_bitmap)->height - padding.top - padding.bottom) * sizeof(uint8_t);
    unsigned int block_equ_size = grid_dim.x * grid_dim.y * sizeof(uint8_t);
    unsigned int grid_equ_size = 1 * sizeof(uint8_t);

    cudaError d_src_malloc_success = cudaMalloc((void**) &d_src_data, data_size);
    cudaError d_dst_malloc_success = cudaMalloc((void**) &d_dst_data, data_size);
    // cudaError d_pixel_equ_malloc_success = cudaMalloc((void**) &d_pixel_equ, pixel_equ_size);
    cudaError d_block_equ_malloc_success = cudaMalloc((void**) &d_block_equ, block_equ_size);
    cudaError d_grid_equ_malloc_success = cudaMalloc((void**) &d_grid_equ, grid_equ_size);

    assert((d_src_malloc_success == cudaSuccess) && "Error: could not allocate memory for d_src_data");
    assert((d_dst_malloc_success == cudaSuccess) && "Error: could not allocate memory for d_dst_data");
    // assert((d_pixel_equ_malloc_success == cudaSuccess) && "Error: could not allocate memory for d_pixel_equ");
    assert((d_block_equ_malloc_success == cudaSuccess) && "Error: could not allocate memory for d_block_equ");
    assert((d_grid_equ_malloc_success == cudaSuccess) && "Error: could not allocate memory for d_grid_equ");

