| OpenCV 3.4.8 Open Source Computer Vision

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cv::cuda::Stream Class Reference
CUDA-accelerated Computer Vision » Core part » Data Structures

This class encapsulates a queue of asynchronous calls. More...

`#include <opencv2/core/cuda.hpp>`

## Public Types
typedef void(* | StreamCallback) (int status, void *userData)

## Public Member Functions
| Stream ()
| creates a new asynchronous stream More...
| Stream (const Ptr< GpuMat::Allocator > &allocator)
| creates a new asynchronous stream with custom allocator More...
void | enqueueHostCallback (StreamCallback callback, void *userData)
| Adds a callback to be called on the host after all currently enqueued items in the stream have completed. More...
| operator bool_type () const
| returns true if stream object is not default (!= 0) More...
bool | queryIfComplete () const
| Returns true if the current stream queue is finished. Otherwise, it returns false. More...
void | waitEvent (const Event &event)
| Makes a compute stream wait on an event. More...
void | waitForCompletion ()
| Blocks the current CPU thread until all operations in the stream are complete. More...

## Static Public Member Functions
static Stream & | Null ()
| return Stream object for default CUDA stream More...

## Friends
class | BufferPool
class | DefaultDeviceInitializer
struct | StreamAccessor

## Detailed Description

This class encapsulates a queue of asynchronous calls.

Note
  Currently, you may face problems if an operation is enqueued twice with different data. Some functions use the constant GPU memory, and next call may update the memory before the previous one has been finished. But calling different operations asynchronously is safe because each operation has its own constant buffer. Memory copy/upload/download/set operations to the buffers you hold are also safe.
  The Stream class is not thread-safe. Please use different Stream objects for different CPU threads.

void thread1()
{
cv::cuda::Stream stream1;
cv::cuda::func1(..., stream1);
}
void thread2()
{
cv::cuda::Stream stream2;
cv::cuda::func2(..., stream2);
}

Note
  By default all CUDA routines are launched in Stream::Null() object, if the stream is not specified by user. In multi-threading environment the stream objects must be passed explicitly (see previous note).

## Member Typedef Documentation

## § StreamCallback

typedef void(* cv::cuda::Stream::StreamCallback) (int status, void *userData)

## Constructor & Destructor Documentation

## § Stream() [1/2]

cv::cuda::Stream::Stream | ( |  | ) |

creates a new asynchronous stream

## § Stream() [2/2]

cv::cuda::Stream::Stream | ( | const Ptr< GpuMat::Allocator > & | allocator | ) |

creates a new asynchronous stream with custom allocator

## Member Function Documentation

## § enqueueHostCallback()

void cv::cuda::Stream::enqueueHostCallback | ( | StreamCallback | callback,
|  | void * | userData
| ) |  |

Adds a callback to be called on the host after all currently enqueued items in the stream have completed.

Note
  Callbacks must not make any CUDA API calls. Callbacks must not perform any synchronization that may depend on outstanding device work or other callbacks that are not mandated to run earlier. Callbacks without a mandated order (in independent streams) execute in undefined order and may be serialized.

## § Null()

static Stream& cv::cuda::Stream::Null | ( |  | ) |
| static

return Stream object for default CUDA stream

## § operator bool_type()

cv::cuda::Stream::operator bool_type | ( |  | ) | const

returns true if stream object is not default (!= 0)

## § queryIfComplete()

bool cv::cuda::Stream::queryIfComplete | ( |  | ) | const

Returns true if the current stream queue is finished. Otherwise, it returns false.

## § waitEvent()

void cv::cuda::Stream::waitEvent | ( | const Event & | event | ) |

Makes a compute stream wait on an event.

## § waitForCompletion()

void cv::cuda::Stream::waitForCompletion | ( |  | ) |

Blocks the current CPU thread until all operations in the stream are complete.

## Friends And Related Function Documentation

## § BufferPool

friend class BufferPool
| friend

## § DefaultDeviceInitializer

friend class DefaultDeviceInitializer
| friend

## § StreamAccessor

friend struct StreamAccessor
| friend

The documentation for this class was generated from the following file:

- opencv2/core/cuda.hpp