This reverts commit d4965495.

This reverts commit ea3e6137.

Gradient implementation for Solve op

Fix gh-4585. Cast the constant to the right dtype.

keep stack trace: fix optimizations or tests (tensor/tests/test_opt.py)

test_local_adv_sub1_adv_inc_sub1.test_stacktrace: refactored and fixed unit test and removed code that was never executed, added missing copy_stack_trace call in the opt.

Pre-instantiating GPUOps

[nit] Fix typo in tensor/basic.txt: lacks a space

Updates and cosmetic changes for config doc

Symbolic Cholesky gradient implementation

Opt related changes.

Better error message

Fix crash during profile optimizer

In get_scalar_constant_value, do not return internal memory of constant

Fix a dependency version to fix travis error

Update doc with instructions for using new gpu backend

Make recent scan opt change deterministic.