void _gs_render(
        const float *sigmas,
        const float *coords,
        const float *colors,
        float *rendered_img,
	const int s, 
	const int h, 
	const int w, 
	const int c,
	const float dmax
);

void _gs_render_backward(
        const float *sigmas,
        const float *coords,
        const float *colors,
        const float *grads,
        float *grads_sigmas,
        float *grads_coords,
        float *grads_colors,
	const int s, 
	const int h, 
	const int w, 
	const int c,
	const float dmax
);