This variable selects the OpenCL platform that Octopus will
use. You can give an explicit platform number or use one of
the options that select a particular vendor
implementation. Platform 0 is used by default.
In order to prevent waste of resources, the code will normally stop when the GPU is disabled due to
incomplete implementations or incompatibilities. AllowCPUonly = yes overrides this and allows the
code execution also in these cases.
If Octopus was compiled with CUDA support and MPI support and if the MPI
implementation is CUDA-aware (i.e., it supports communication using device pointers),
this switch can be set to true to use the CUDA-aware MPI features. The advantage
of this approach is that it can do, e.g., peer-to-peer copies between devices without
going through the host memory.
The default is false, except when the configure switch –enable-cudampi is set, in which
case this variable is set to true.
If Octopus was compiled with OpenCL or CUDA support, it will
try to initialize and use an accelerator device. By setting this
variable to yes you force Octopus not to use an accelerator even it is available.