[STF] Use a reduce access mode to compute residuals

[caugonnet]

Compute residuals using a reduce access mode rather than a sequential code on the host

Which kernels are implemented?

• [ ] synch_p2p (p2p)
• [ ] stencil
• [ ] transpose
• [ ] nstream
• [x] dgemm
• [ ] reduce
• [ ] sparse
• [ ] branch
• [ ] random
• [ ] refcount
• [ ] synch_global
• [ ] PIC
• [ ] AMR

Do you certify that your contribution is made in good faith and does not attempt to introduce any negative behavior into this project?

• [x] Yes
• [ ] No

[jeffhammond]

You tested this locally already, right?

[caugonnet]

Yes but it is not ready for merge (i thought it was a draft PR actually !), i need to adapt more kernels