Revert "remove the useless code optimization for matrix mulitiplication"

This reverts commit 1c39d9b2ac6a467482b0cb514c766d3c6c885001.
Revert "chang the order of matrix multiplication to gain improvement"

This reverts commit 7b8cf6d68433710e7aa10139e04b79c2b70d2c9e.
Revert "enable unit test"

This reverts commit 9babe6542d10c65feb00bff820f00b6d14a40ab0.
add corresponding Matlab code for the LaplacianInferenceMethod_unittest