Fixed by checking if tile needs to be re-created

[jubueche]

Related issues

Issue #609

Description

Tile is re-created and reference between optimizer and tile is cut.

Details

For the torch tile, we don't re-create the tile unless we need to.

[jubueche]

@maljoras @kkvtran there seem to be some rounding issues in the tests.

[jubueche]

@kkvtran there is an issue in the tests with python 3.8 in a part of the code that I didn't touch.

[kkvtran]

I restarted the travis builds and everything built successfully now.