get different values when run Ex2_LinearRegression.java in many times

#### Issue Description

Please describe your issue, along with:

in this example https://github.com/eclipse/deeplearning4j-examples/blob/master/samediff-examples/src/main/java/org/nd4j/examples/samediff/quickstart/basics/Ex2_LinearRegression.java why gradMap.get("weights") and gradMap.get("bias") return me different value when I run it in many times ?

- expected gradMap.get("weights") and gradMap.get("bias") return the same values when run it in many times
- encountered gradMap.get("weights") and gradMap.get("bias") return me different values when run it in many times

#### Version Information

Please indicate relevant versions, including, if relevant:

* Deeplearning4j version: beta7
* platform information (OS, etc): mac OS10.15.6
* CUDA version, if used: None
* NVIDIA driver version, if in use: None