aclrtCreateContext

Description

Creates a context explicitly in the current process or thread.

For the Atlas 200/300/500 Inference Product, the context contains two streams: one default stream and one stream for internal synchronization.

For the Atlas Training Series Product, the context contains one default stream.

If aclrtSetDevice is not called in the application, when aclrtCreateContext is called for the first time, the system binds a default stream to the device based on the device ID passed by the API (one device is bound to only one default stream). Therefore, when aclrtCreateContext is called for the first time, the number of occupied streams is calculated as follows: Number of occupied streams = Number of default streams bound to the device + Number of streams contained in the context.

Restrictions

The following use cases are supported:

• If aclrtCreateContext is not called to explicitly create a context, the system uses the default context, which is created implicitly with the aclrtSetDevice call.
  • Implicit context creation: applies to simple apps with low complicity of interaction logic. However, in multithreaded programming, the execution result depends on the thread scheduling sequence.
  • Explicit context creation: applies to large apps with complex interaction logic, offering better app readability and maintainability.
• If a device is specified in a process, multiple threads in the process can share the context explicitly created on the device by calling aclrtCreateContext.
• If multiple contexts are created in a process, the current thread can use only one context at a time. It is recommended that aclrtSetCurrentContext be used to specify the context of the current thread to improve program maintainability. (The number of contexts depends on the number of streams. For details, see aclrtCreateStream.)

Prototype

aclError aclrtCreateContext(aclrtContext *context, int32_t deviceId)

Parameters

Returns

The value 0 indicates success, and other values indicate failure. For details, see aclError.