force delete packages before unit test

fix gpu_img_conv2 float precision issue

using one thread to dump sequential output

'numpy.ndarray' object has no attribute 'tobytes'

run python tests in virtualenv

keep debugging

debug

add verbose output for unit test

When using system python, "pip install" needs root previlege. Using virtualenv to avoid this.

accelerate test and add debug info

Avoid relink executables when cmake files are changed

add missing api doc of network and evaluator

Fix dynamic loading of Lapack caused by #1958

This only fixes the issue for ATLAS
MKL is still another fix.

In the original util.cmake. enable_virtualenv.c is always regenerated when cmake files are changed, which leads to the relinking of all the targets depends on paddle_utils.

modify function build_dict of dataset imikolov

remove gfortran and dlopen lapack libs

merge commit on Release/0.10.0 branch to develop branch