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Author Topic: Max mem alloc size  (Read 5166 times)

olihar

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Max mem alloc size
« on: November 12, 2014, 12:51:37 PM »
Why is there max mem alloc 1536 MB for a card with 6144 MB global memory?

Quote
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

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Re: Max mem alloc size
« Reply #1 on: August 19, 2015, 10:22:17 AM »
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

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Re: Max mem alloc size
« Reply #2 on: August 19, 2015, 10:58:34 AM »
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
With best regards,
Dmitry Semyonov
Agisoft