    def update(self, W, block_size, n_centroids):
        """
        Updates the running statistics when quantizing a new layer.
        """

        # bits per weights
        bits_per_weight = np.log2(n_centroids) / block_size
        self.n_quantized_layers += 1

        # size of indexing the subvectors of size block_size (in MB)
        size_index_layer = bits_per_weight * W.numel() / 8 / 1024 / 1024
        self.size_index += size_index_layer

        # size of the centroids stored in float16 (in MB)
        size_centroids_layer = n_centroids * block_size * 2 / 1024 / 1024
        self.size_centroids += size_centroids_layer

        # size of non-compressed layers, e.g. LayerNorms or biases (in MB)
        size_uncompressed_layer = W.numel() * 4 / 1024 / 1024
        self.size_non_quantized -= size_uncompressed_layer
Updates the running statistics when quantizing a new layer.
fairseq/modules/quantization/pq/utils.py