USE_HOST_POINTER at same time as VRAM-only in QPager?

unitaryfund / qrack

Comprehensive, GPU accelerated framework for developing universal virtual quantum processors

https://qrack.readthedocs.io/en/latest/

GNU Lesser General Public License v3.0

176 stars 38 forks source link

USE_HOST_POINTER at same time as VRAM-only in QPager? #937

Closed WrathfulSpatula closed 2 years ago

WrathfulSpatula commented 2 years ago

I'm not sure whether QPager is capable of effectively doubling capacity (for 1 extra total qubit) by using as many USE_HOST_POINTER pages as VRAM-only pages.

Hypothetically, it might turn out it definitely can't, depending on the direct memory access controller ("DMAC"). However, this might depend on whether the GPU/accelerator involved has sufficiently modern DMA technology.

It's worth looking into.

WrathfulSpatula commented 2 years ago

In effect, this has been achieved by the environment variable QRACK_QPAGER_DEVICES_HOST_POINTER, as its purpose and usage is explained in the README.