MindSpore报Dead code exist, please remove it.

1 报错描述

MindSpore报Dead code exist, please remove it.

1.1 系统环境
*Hardware Environment(Ascend/GPU/CPU): Ascend/GPU/CPU

Software Environment:

– MindSpore version (source or binary): master or 1.6.0

– Python version (e.g., Python 3.7.5): 3.7.6

– OS platform and distribution (e.g., Linux Ubuntu 16.04): Ubuntu 4.15.0-74-generic

– GCC/Compiler version (if compiled from source):

 

1.2 基本信息
1.2.1 脚本

例1：

import numpy as np
from mindspore import Tensor, nn
from mindspore import dtype as ms

class IfInWhileNet(nn.Cell):

    def __init__(self):
        super().__init__()
        self.nums = [1, 2, 3]

    def construct(self, x, y, i):
        out = x
        while i < 3:
            i = i + 1
            out = out + 1
            if x == 2:
                break
                # Dead code here
                out = out + y
        return out

forward_net = IfInWhileNet()
i = Tensor(np.array(0), dtype=ms.int32)
x = Tensor(np.array(0), dtype=ms.int32)
y = Tensor(np.array(1), dtype=ms.int32)

output = forward_net(x, y, i)

 

1.2.2报错信息

RuntimeError: mindspore/ccsrc/pipeline/jit/parse/parse.cc:696 ParseStatements] Dead code exist, please remove it.

# In file test_while.py(20)
                out = out + y

 

原因分析：

在while循环里面存在break语句，break语句后面的“out = out +  y”实际上是一个冗余语句，因为该语句永远都不会被执行。

 

2 解决方法
基于上面已知的原因，很容易做出如下修改：

import numpy as np
from mindspore import Tensor, nn
from mindspore import dtype as ms

class IfInWhileNet(nn.Cell):

    def __init__(self):
        super().__init__()
        self.nums = [1, 2, 3]

    def construct(self, x, y, i):
        out = x
        while i < 3:
            i = i + 1
            out = out + 1
            if x == 2:
                break
                # Dead code here
                #out = out + y
        return out

forward_net = IfInWhileNet()
i = Tensor(np.array(0), dtype=ms.int32)
x = Tensor(np.array(0), dtype=ms.int32)
y = Tensor(np.array(1), dtype=ms.int32)

output = forward_net(x, y, i)

注释掉或者删除掉“out = out +  y”这个冗余语句后，测试脚本执行成功。

 

3 总结
break/continue/return 这种流程跳转语句后面不要写任何冗余不执行语句，会导致报Dead code异常。