Istvan Kiss
b271963c51
Change-Id: I179814351b77935aff55e8ae47dd322a3e15a868
[ROCm/hip commit: f39c7a3150]
108 строки
3.8 KiB
ReStructuredText
108 строки
3.8 KiB
ReStructuredText
.. meta::
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:description: Initialization.
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:keywords: AMD, ROCm, HIP, initialization
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.. _initialization:
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********************************************************************************
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Initialization
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********************************************************************************
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The initialization involves setting up the environment and resources needed for
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using GPUs. The following steps are covered with the initialization:
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- Setting up the HIP runtime
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This includes reading the environment variables set during init, setting up
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the active or visible devices, loading necessary libraries, setting up
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internal buffers for memory copies or cooperative launches, initialize the
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compiler as well as HSA runtime and checks any errors due to lack of resources
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or no active devices.
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- Querying and setting GPUs
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Identifying and querying the available GPU devices on the system.
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- Setting up contexts
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Creating contexts for each GPU device, which are essential for managing
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resources and executing kernels. For further details, check the :ref:`context
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section <context_driver_api>`.
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Initialize the HIP runtime
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================================================================================
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The HIP runtime is initialized automatically when the first HIP API call is
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made. However, you can explicitly initialize it using :cpp:func:`hipInit`,
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to be able to control the timing of the initialization. The manual
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initialization can be useful to ensure that the GPU is initialized and
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ready, or to isolate GPU initialization time from other parts of
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your program.
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.. note::
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You can use :cpp:func:`hipDeviceReset` to delete all streams created, memory
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allocated, kernels running and events created by the current process. Any new
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HIP API call initializes the HIP runtime again.
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Querying and setting GPUs
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================================================================================
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If multiple GPUs are available in the system, you can query and select the
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desired GPU(s) to use based on device properties, such as size of global memory,
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size shared memory per block, support of cooperative launch and support of
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managed memory.
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Querying GPUs
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--------------------------------------------------------------------------------
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The properties of a GPU can be queried using :cpp:func:`hipGetDeviceProperties`,
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which returns a struct of :cpp:struct:`hipDeviceProp_t`. The properties in the
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struct can be used to identify a device or give an overview of hardware
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characteristics, that might make one GPU better suited for the task than others.
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The :cpp:func:`hipGetDeviceCount` function returns the number of available GPUs,
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which can be used to loop over the available GPUs.
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Example code of querying GPUs:
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.. code-block:: cpp
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#include <hip/hip_runtime.h>
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#include <iostream>
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int main() {
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int deviceCount;
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if (hipGetDeviceCount(&deviceCount) == hipSuccess){
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for (int i = 0; i < deviceCount; ++i){
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hipDeviceProp_t prop;
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if ( hipGetDeviceProperties(&prop, i) == hipSuccess)
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std::cout << "Device" << i << prop.name << std::endl;
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}
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}
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return 0;
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}
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Setting the GPU
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--------------------------------------------------------------------------------
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:cpp:func:`hipSetDevice` function select the GPU to be used for subsequent HIP
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operations. This function performs several key tasks:
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- Context Binding
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Binds the current thread to the context of the specified GPU device. This
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ensures that all subsequent operations are executed on the selected device.
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- Resource Allocation
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Prepares the device for resource allocation, such as memory allocation and
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stream creation.
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- Check device availability
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Checks for errors in device selection and returns error if the specified
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device is not available or not capable of executing HIP operations.
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