Max mem alloc size

[olihar]

Why is there max mem alloc 1536 MB for a card with 6144 MB global memory?

Using device: GeForce GTX TITAN Black, 15 compute units, 6144 MB global memory
  max work group size 1024
  max work item sizes [1024, 1024, 64]
  max mem alloc size 1536 MB

1536 / 8 = 192
6144 / 8 = 768

Or does Photoscan reconstruction chunks work with 1536 MB max?

[tmr]

I'd like to second this question, although it is from last year - there was no answer from Agisoft and it still seems to be a potential issue.

I came here because I was looking for an answer why PS seems to be using only a third of my GPU memory:

Using device: Tahiti, 28 compute units, 2848 MB global memory
  max work group size 256
  max work item sizes [256, 256, 256]
  max mem alloc size 1024 MB
Initializing...

Any ideas? Thanks!

[Dmitry Semyonov]

Hello olihar,

CL_DEVICE_MAX_MEM_ALLOC_SIZE represents a maximum size of a buffer that can be allocated at once. It might be still possible to allocate more memory with multiple buffer allocations.

OpenCL requires CL_DEVICE_MAX_MEM_ALLOC_SIZE to be at least 1/4 of CL_DEVICE_GLOBAL_MEM_SIZE:
https://www.khronos.org/registry/cl/sdk/1.0/docs/man/xhtml/clGetDeviceInfo.html