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<div class="section-link"><a href="api-sync-behavior.html#api-sync-behavior">1. API synchronization behavior </a></div>
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<div class="section-link"><a href="stream-sync-behavior.html#stream-sync-behavior">2. Stream synchronization behavior</a></div>
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<div class="section-link"><a href="modules.html#modules">3. Modules</a></div>
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<div class="section-link"><a href="group__CUDART__DEVICE.html#group__CUDART__DEVICE">3.1. Device Management</a></div>
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<div class="section-link"><a href="group__CUDART__THREAD__DEPRECATED.html#group__CUDART__THREAD__DEPRECATED">3.2. Thread Management [DEPRECATED]</a></div>
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<div class="section-link"><a href="group__CUDART__ERROR.html#group__CUDART__ERROR">3.3. Error Handling</a></div>
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<div class="section-link"><a href="group__CUDART__STREAM.html#group__CUDART__STREAM">3.4. Stream Management</a></div>
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<div class="section-link"><a href="group__CUDART__EVENT.html#group__CUDART__EVENT">3.5. Event Management</a></div>
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<div class="section-link"><a href="group__CUDART__EXECUTION.html#group__CUDART__EXECUTION">3.6. Execution Control</a></div>
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<div class="section-link"><a href="group__CUDART__OCCUPANCY.html#group__CUDART__OCCUPANCY">3.7. Occupancy</a></div>
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<div class="section-link"><a href="group__CUDART__MEMORY.html#group__CUDART__MEMORY">3.8. Memory Management</a></div>
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<div class="section-link"><a href="group__CUDART__UNIFIED.html#group__CUDART__UNIFIED">3.9. Unified Addressing</a></div>
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<div class="section-link"><a href="group__CUDART__PEER.html#group__CUDART__PEER">3.10. Peer Device Memory Access</a></div>
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<div class="section-link"><a href="group__CUDART__OPENGL.html#group__CUDART__OPENGL">3.11. OpenGL Interoperability</a></div>
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<div class="section-link"><a href="group__CUDART__OPENGL__DEPRECATED.html#group__CUDART__OPENGL__DEPRECATED">3.12. OpenGL Interoperability [DEPRECATED]</a></div>
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<div class="section-link"><a href="group__CUDART__D3D9.html#group__CUDART__D3D9">3.13. Direct3D 9 Interoperability</a></div>
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<div class="section-link"><a href="group__CUDART__D3D9__DEPRECATED.html#group__CUDART__D3D9__DEPRECATED">3.14. Direct3D 9 Interoperability [DEPRECATED]</a></div>
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<div class="section-link"><a href="group__CUDART__D3D10.html#group__CUDART__D3D10">3.15. Direct3D 10 Interoperability</a></div>
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<div class="section-link"><a href="group__CUDART__D3D10__DEPRECATED.html#group__CUDART__D3D10__DEPRECATED">3.16. Direct3D 10 Interoperability [DEPRECATED]</a></div>
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<div class="section-link"><a href="group__CUDART__D3D11.html#group__CUDART__D3D11">3.17. Direct3D 11 Interoperability</a></div>
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<div class="section-link"><a href="group__CUDART__D3D11__DEPRECATED.html#group__CUDART__D3D11__DEPRECATED">3.18. Direct3D 11 Interoperability [DEPRECATED]</a></div>
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<div class="section-link"><a href="group__CUDART__TEXTURE.html#group__CUDART__TEXTURE">3.21. Texture Reference Management</a></div>
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<div class="section-link"><a href="group__CUDART__HIGHLEVEL.html#group__CUDART__HIGHLEVEL">3.26. C++ API Routines</a></div>
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<div class="section-link"><a href="annotated.html#annotated">4. Data Structures</a></div>
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<div class="section-link"><a href="class____cudaOccupancyB2DHelper.html#class____cudaOccupancyB2DHelper">4.1. __cudaOccupancyB2DHelper</a></div>
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<div class="section-link"><a href="structcudaChannelFormatDesc.html#structcudaChannelFormatDesc">4.2. cudaChannelFormatDesc</a></div>
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<div class="section-link"><a href="structcudaDeviceProp.html#structcudaDeviceProp">4.3. cudaDeviceProp</a></div>
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<div class="section-link"><a href="structcudaFuncAttributes.html#structcudaFuncAttributes">4.5. cudaFuncAttributes</a></div>
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<div class="section-link"><a href="structcudaIpcEventHandle__t.html#structcudaIpcEventHandle__t">4.6. cudaIpcEventHandle_t</a></div>
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<div class="section-link"><a href="structcudaIpcMemHandle__t.html#structcudaIpcMemHandle__t">4.7. cudaIpcMemHandle_t</a></div>
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<div class="section-link"><a href="structcudaMemcpy3DParms.html#structcudaMemcpy3DParms">4.8. cudaMemcpy3DParms</a></div>
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<div class="section-link"><a href="structcudaMemcpy3DPeerParms.html#structcudaMemcpy3DPeerParms">4.9. cudaMemcpy3DPeerParms</a></div>
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<div class="section-link"><a href="structcudaPitchedPtr.html#structcudaPitchedPtr">4.10. cudaPitchedPtr</a></div>
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<div class="section-link"><a href="structcudaPointerAttributes.html#structcudaPointerAttributes">4.11. cudaPointerAttributes</a></div>
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<div class="section-link"><a href="structcudaPos.html#structcudaPos">4.12. cudaPos</a></div>
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<div class="section-link"><a href="structcudaResourceDesc.html#structcudaResourceDesc">4.13. cudaResourceDesc</a></div>
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<div class="section-link"><a href="structcudaResourceViewDesc.html#structcudaResourceViewDesc">4.14. cudaResourceViewDesc</a></div>
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<div class="section-link"><a href="structcudaTextureDesc.html#structcudaTextureDesc">4.15. cudaTextureDesc</a></div>
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<div class="section-link"><a href="structsurfaceReference.html#structsurfaceReference">4.16. surfaceReference</a></div>
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<div class="section-link"><a href="structtextureReference.html#structtextureReference">4.17. textureReference</a></div>
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<div class="section-link"><a href="functions.html#functions">5. Data Fields</a></div>
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<article id="contents">
<div class="topic nested1" id="stream-sync-behavior"><a name="stream-sync-behavior" shape="rect">
<!-- --></a><h2 class="topictitle2">2. Stream synchronization behavior</h2>
<div class="body refbody">
<div class="section" id="stream-sync-behavior__null-stream"><a name="stream-sync-behavior__null-stream" shape="rect">
<!-- --></a><h2 class="title sectiontitle">NULL stream</h2>
<p class="p">
The NULL stream or stream 0 is an implicit stream which synchronizes with all other streams in the same <samp class="ph codeph">CUcontext</samp> except for non-blocking streams, described below.
(For applications using the runtime APIs only, there will be one context per device.)
When an action is taken in the NULL stream such as a kernel launch or <samp class="ph codeph">cudaStreamWaitEvent()</samp>, the NULL stream first waits on all blocking streams, the action is queued in the NULL stream, and then all blocking streams
wait on the NULL stream.
</p>
<p class="p">
For example, the following code launches a kernel <samp class="ph codeph">k_1</samp> in stream <samp class="ph codeph">s</samp>, then <samp class="ph codeph">k_2</samp> in the NULL stream, then <samp class="ph codeph">k_3</samp> in stream <samp class="ph codeph">s</samp>:
</p><pre xml:space="preserve">
k_1<<<1, 1, 0, s>>>();
k_2<<<1, 1>>>();
k_3<<<1, 1, 0, s>>>();</pre><p class="p">
The resulting behavior is that <samp class="ph codeph">k_2</samp> will block on <samp class="ph codeph">k_1</samp> and <samp class="ph codeph">k_3</samp> will block on <samp class="ph codeph">k_2</samp>.
</p>
<p class="p">
Actions are added in the NULL stream by passing <samp class="ph codeph">0</samp> as the <samp class="ph codeph">cudaStream_t</samp> parameter of applicable APIs, or by calling the corresponding synchronous APIs which do not take the <samp class="ph codeph">cudaStream_t</samp> parameter.
The NULL stream is also the default for kernel launches if a stream is not specified.
</p>
<p class="p">
Non-blocking streams which do not synchronize with the NULL stream can be created using the <samp class="ph codeph">cudaStreamNonBlocking</samp> flag with the stream creation APIs.
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