How do I get Cycles to use GPU on a linux server?

Question

Inspired by this question: Enabling GPU rendering for Cycles?

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I have access to a Linux server that is equipped with GeForce GTX TITAN X. Now Cycles still renders everything with CPU. How can I get it to exploit the GPU?

Since I am talking about a Linux server, I guess there are two steps towards this goal:

1. How to get the GPU ID or identifier with Unix commands so that I can refer to it in Blender?
2. How to use Python to enable GPU computations?

Answer 1

For enabling the device for use, see bpy.context.user_preferences.system.compute_device_type and
bpy.context.user_preferences.system.compute_device.

To check these from a shell, put the python you wish to execute in a file and run

blender --background --python <file.py>

Or, more concisely for quick tests,

blender -b --python-expr 'import bpy; <python code here>'

For convenience, here's a script which will print the possible and current values of compute_device_type and compute_device:

import bpy

sysp = bpy.context.user_preferences.system

devt = sysp.compute_device_type
dev = sysp.compute_device

# get list of possible values of enum, see http://blender.stackexchange.com/a/2268/599
devt_list = sysp.bl_rna.properties['compute_device_type'].enum_items.keys()
dev_list = sysp.bl_rna.properties['compute_device'].enum_items.keys()

# pretty print
lines=[
("Property", "Value", "Possible Values"),
("Device Type:", devt, str(devt_list)),
("Device:", dev, str(dev_list)),
]
print("\nGPU compute configuration:")
for l in lines:
    print("{0:<20} {1:<20} {2:<50}".format(*l))

If CUDA shows up in the possible values for device type, then enabling the device should be as simple as doing something like this in python:

devt = sysp.compute_device_type = 'CUDA'
dev = sysp.compute_device = 'CUDA_0'

To find the identifier for the device, you can use the script above with a line to set compute_device_type to CUDA before getting the list of possible devices.

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Once that's all enabled we must still tell cycles to actually use it; to do this set bpy.context.scene.cycles.device to GPU.