def get_trim_len(self):
        """how much of memory can be trimmed to reduce computation"""
        L = self._max_span
        trim_len = min(L - 1, L - self._mask.get_current_max_size())
        # too fine granularity might be bad for the memory management
        trim_len = math.floor(trim_len / 64) * 64
        return trim_len
how much of memory can be trimmed to reduce computation
understand_icl/fairseq/examples/adaptive_span/adaptive_span_attention.py