pip install mxnet: illegal instruction

无法 import mxnet 之前一直用的好好的,今天突然出毛病了。我用的是linux cpu 版本, install: pip install mxnet --pre

Python 3.6.5 |Anaconda, Inc.| (default, Mar 29 2018, 18:21:58) 
[GCC 7.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import mxnet as mx
Illegal instruction

去掉--pre就成功了, 但是官网的说明是要--pre, 有什么区别? https://mxnet.incubator.apache.org/install/index.html?device=Linux&language=Python&processor=CPU

不加–pre 是安装最新稳定版
–pre 是安装预发布版本