[Matrix]: avoid partitioning local matrices in materialize_*
[Matrix]: avoid partitioning local matrices in materialize_*

This is experimental. I need to measure the performance more carefully.

icoming/FlashX,icoming/FlashX,icoming/FlashGraph,flashxio/FlashX,icoming/FlashX,flashxio/FlashX,flashxio/FlashX,flashxio/FlashX,icoming/FlashX,icoming/FlashGraph,icoming/FlashGraph,icoming/FlashGraph,icoming/FlashX,icoming/FlashGraph,flashxio/FlashX,flashxio/FlashX