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Return a list of physical devices visible to the host runtime.

Used in the notebooks

Used in the guide Used in the tutorials

Physical devices are hardware devices present on the host machine. By default all discovered CPU and GPU devices are considered visible.

This API allows querying the physical hardware resources prior to runtime initialization. Thus, giving an opportunity to call any additional configuration APIs. This is in contrast to tf.config.list_logical_devices, which triggers runtime initialization in order to list the configured devices.

The following example lists the number of visible GPUs on the host.

physical_devices = tf.config.list_physical_devices('GPU')
print("Num GPUs:", len(physical_devices))
Num GPUs: ...

However, the number of GPUs available to the runtime may change during runtime initialization due to marking certain devices as not visible or configuring multiple logical devices.

device_type (optional string) Only include devices matching this device type. For example "CPU" or "GPU".

List of discovered tf.config.PhysicalDevice objects