Revert "Spars Matrix"

This reverts commit e98ca83642afdcd1b08ad1b736ec68615d6f842c.
Revert "Revert "Spars Matrix""

This reverts commit 6ff45aea63b510c8780e5833d5382553eba91d86.
Revert "Revert "Revert "Spars Matrix"""

This reverts commit ec6bf9ce4936b51e60f01330e7478ad19683c1c2.