period.py 文件源码

def calculate_max_drawdown(self):
        compounded_returns = []
        cur_return = 0.0
        for r in self.algorithm_returns:
            try:
                cur_return += math.log(1.0 + r)
            # this is a guard for a single day returning -100%, if returns are
            # greater than -1.0 it will throw an error because you cannot take
            # the log of a negative number
            except ValueError:
                log.debug("{cur} return, zeroing the returns".format(
                    cur=cur_return))
                cur_return = 0.0
            compounded_returns.append(cur_return)

        cur_max = None
        max_drawdown = None
        for cur in compounded_returns:
            if cur_max is None or cur > cur_max:
                cur_max = cur

            drawdown = (cur - cur_max)
            if max_drawdown is None or drawdown < max_drawdown:
                max_drawdown = drawdown

        if max_drawdown is None:
            return 0.0

        return 1.0 - math.exp(max_drawdown)