---
name: "clFlush"
section: "3clc"
platform: "linux"
package: "opencl-1.2-man-doc"
version: "1.0~svn33624-5.1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/clFlush"
---

# clFlush(3clc)

Issues all previously queued OpenCL commands in a command-queue to the device associated with the command-queue.

## NAME

clFlush - Issues all previously queued OpenCL commands in a command-queue to the device associated with the command-queue.

##

**cl\_int clFlush(cl\_command\_queue** *command\_queue***);**

## NOTES

Issues all previously queued OpenCL commands in *command\_queue* to the device associated with *command\_queue*.

**clFlush** only guarantees that all queued commands to *command\_queue* will eventually be submitted to the appropriate device There is no guarantee that they will be complete after **clFlush** returns.

Any blocking commands queued in a command-queue and [**clReleaseCommandQueue**(3clc)](/clReleaseCommandQueue/3clc.md) perform an implicit flush of the command-queue. These blocking commands are [**clEnqueueReadBuffer**(3clc)](/clEnqueueReadBuffer/3clc.md), [**clEnqueueReadBufferRect**(3clc)](/clEnqueueReadBufferRect/3clc.md), or [**clEnqueueReadImage**(3clc)](/clEnqueueReadImage/3clc.md) with *blocking\_read* set to **CL\_TRUE**; [**clEnqueueWriteBuffer**(3clc)](/clEnqueueWriteBuffer/3clc.md), [**clEnqueueWriteBufferRect**(3clc)](/clEnqueueWriteBufferRect/3clc.md), or [**clEnqueueWriteImage**(3clc)](/clEnqueueWriteImage/3clc.md) with *blocking\_write* set to **CL\_TRUE**; [**clEnqueueMapBuffer**(3clc)](/clEnqueueMapBuffer/3clc.md) or [**clEnqueueMapImage**(3clc)](/clEnqueueMapImage/3clc.md) with *blocking\_map* set to **CL\_TRUE**; or [**clWaitForEvents**(3clc)](/clWaitForEvents/3clc.md).

To use event objects that refer to commands enqueued in a command-queue as event objects to wait on by commands enqueued in a different command-queue, the application must call a **clFlush** or any blocking commands that perform an implicit flush of the command-queue where the commands that refer to these event objects are enqueued.

## ERRORS

Returns CL\_SUCCESS if the function call was executed successfully. Otherwise, it returns one of the following:

• CL\_INVALID\_COMMAND\_QUEUE if *command\_queue* is not a valid command-queue.

• CL\_OUT\_OF\_HOST\_MEMORY if there is a failure to allocate resources required by the OpenCL implementation on the host.

• CL\_OUT\_OF\_RESOURCES if there is a failure to allocate resources required by the OpenCL implementation on the device.

## SPECIFICATION

**OpenCL Specification**\[1\]

## SEE ALSO

[**clFinish**(3clc)](/clFinish/3clc.md)

## AUTHORS

**The Khronos Group**

## COPYRIGHT

Copyright © 2007-2011 The Khronos Group Inc.\
 Permission is hereby granted, free of charge, to any person obtaining a copy of this software and/or associated documentation files (the "Materials"), to deal in the Materials without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Materials, and to permit persons to whom the Materials are furnished to do so, subject to the condition that this copyright notice and permission notice shall be included in all copies or substantial portions of the Materials.

## NOTES

- 1\.

  OpenCL Specification

  page 193, section 5.13 - Flush and Finish