code: function(opt) {
      var opt = opt || {};
  
      // computed
      this.out_sx = opt.in_sx;
      this.out_sy = opt.in_sy;
      this.out_depth = opt.in_depth;
      this.layer_type = 'dropout';
      this.drop_prob = typeof opt.drop_prob !== 'undefined' ? opt.drop_prob : 0.5;
      this.dropped = global.zeros(this.out_sx*this.out_sy*this.out_depth);
    }
docs: An inefficient dropout layer Note this is not most efficient implementation since the layer before computed all these activations and now we're just going to drop them :( same goes for backward pass. Also, if we wanted to be efficient at test time we could equivalently be clever and upscale during train and copy pointers during test todo: make more efficient.