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66 lines
2.5 KiB
TeX
66 lines
2.5 KiB
TeX
\pagebreak
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\section{Traits for Specifying Devices}
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\label{sec:device_env_traits}
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\index{environment variables!OMP_AVAILABLE_DEVICES@\kcode{OMP_AVAILABLE_DEVICES}}
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\index{OMP_AVAILABLE_DEVICES@\kcode{OMP_AVAILABLE_DEVICES}}
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\index{environment variables!OMP_DEFAULT_DEVICE@\kcode{OMP_DEFAULT_DEVICE}}
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\index{OMP_DEFAULT_DEVICE@\kcode{OMP_DEFAULT_DEVICE}}
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Environment variables \kcode{OMP_AVAILABLE_DEVICES} and
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\kcode{OMP_DEFAULT_DEVICE} can take traits to specify the available
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devices and the default device, respectively.
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In addition, \kcode{OMP_DEFAULT_DEVICE} can also take an integer
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as a device number to specify the default device.
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The following examples show how traits are used to specify devices
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for these environment variables.
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Only GPU non-host devices are available to program:
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\begin{boxedcode}
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export OMP_AVAILABLE_DEVICES=\ucode{"kind(gpu)"}
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\end{boxedcode}
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Order of available devices would be all vendor \ucode{A} GPUs, then
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the rest of the non-host devices as specified by "\ucode{*}":
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\begin{boxedcode}
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export OMP_AVAILABLE_DEVICES=\ucode{"kind(gpu)&&vendor(A),*"}
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\end{boxedcode}
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Available devices would be all non-gpu devices from vendor \ucode{A}:
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\begin{boxedcode}
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export OMP_AVAILABLE_DEVICES=\ucode{"!kind(gpu)&&vendor(A)"}
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\end{boxedcode}
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Available devices start with 1 vendor \ucode{A} GPU device, then
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2 vendor \ucode{B} GPU devices, and then the rest of the non-host devices:
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\begin{boxedcode}
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export OMP_AVAILABLE_DEVICES=\ucode{"(kind(gpu)&&vendor(A))[0],}
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\ucode{(kind(gpu)&&vendor(B))[0:2],*"}
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\end{boxedcode}
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The device number range is specified by the C/C++ array section syntax
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\ucode{[0:2]} where "\ucode{0}" is the first index and "\ucode{2}"
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is the length.
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Three available devices are re-ordered with "\ucode{uid-gpu3}" corresponding
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to device 0, "\ucode{uid-gpu2}" to device 1 and "\ucode{uid-gpu1}"
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to device 2:
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\begin{boxedcode}
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export OMP_AVAILABLE_DEVICES=\ucode{"uid(uid-gpu3),uid(uid-gpu2),}
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\ucode{uid(uid-gpu1)"}
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\end{boxedcode}
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The default device will be some visible vendor \ucode{A} GPU device.
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If not available, then set to initial device:
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\begin{boxedcode}
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export OMP_DEFAULT_DEVICE=\ucode{"kind(gpu)&&vendor(A),initial"}
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\end{boxedcode}
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The default device will be some visible vendor \ucode{A} GPU device.
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If not available, then set to invalid device so that upon first use of default
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device the program will error out:
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\begin{boxedcode}
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export OMP_DEFAULT_DEVICE=\ucode{"kind(gpu)&&vendor(A),invalid"}
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\end{boxedcode}
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