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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__CUDA__TYPES.html#group__CUDA__TYPES">3.1. Data types used by CUDA driver</a></div>
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<div class="section-link"><a href="group__CUDA__ERROR.html#group__CUDA__ERROR">3.2. Error Handling</a></div>
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<div class="section-link"><a href="group__CUDA__INITIALIZE.html#group__CUDA__INITIALIZE">3.3. Initialization</a></div>
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<div class="section-link"><a href="group__CUDA__DEVICE.html#group__CUDA__DEVICE">3.5. Device Management</a></div>
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<div class="section-link"><a href="group__CUDA__DEVICE__DEPRECATED.html#group__CUDA__DEVICE__DEPRECATED">3.6. Device Management [DEPRECATED]</a></div>
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<div class="section-link"><a href="group__CUDA__CTX.html#group__CUDA__CTX">3.7. Context Management</a></div>
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<div class="section-link"><a href="group__CUDA__CTX__DEPRECATED.html#group__CUDA__CTX__DEPRECATED">3.8. Context Management [DEPRECATED]</a></div>
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<div class="section-link"><a href="group__CUDA__MEM.html#group__CUDA__MEM">3.10. Memory Management</a></div>
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<div class="section-link"><a href="group__CUDA__UNIFIED.html#group__CUDA__UNIFIED">3.11. Unified Addressing</a></div>
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<div class="section-link"><a href="group__CUDA__STREAM.html#group__CUDA__STREAM">3.12. Stream Management</a></div>
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<div class="section-link"><a href="group__CUDA__EXEC.html#group__CUDA__EXEC">3.14. Execution Control</a></div>
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<div class="section-link"><a href="group__CUDA__EXEC__DEPRECATED.html#group__CUDA__EXEC__DEPRECATED">3.15. Execution Control [DEPRECATED]</a></div>
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<div class="section-link"><a href="group__CUDA__OCCUPANCY.html#group__CUDA__OCCUPANCY">3.16. Occupancy</a></div>
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<div class="section-link"><a href="group__CUDA__TEXREF.html#group__CUDA__TEXREF">3.17. Texture Reference Management</a></div>
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<div class="section-link"><a href="group__CUDA__TEXREF__DEPRECATED.html#group__CUDA__TEXREF__DEPRECATED">3.18. Texture Reference Management [DEPRECATED]</a></div>
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<div class="section-link"><a href="group__CUDA__GRAPHICS.html#group__CUDA__GRAPHICS">3.23. Graphics Interoperability</a></div>
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<div class="section-link"><a href="group__CUDA__D3D9__DEPRECATED.html#group__CUDA__D3D9__DEPRECATED">3.26.1. Direct3D 9 Interoperability [DEPRECATED]</a></div>
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<div class="section-link"><a href="group__CUDA__D3D11__DEPRECATED.html#group__CUDA__D3D11__DEPRECATED">3.28.1. Direct3D 11 Interoperability [DEPRECATED]</a></div>
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<div class="section-link"><a href="group__CUDA__VDPAU.html#group__CUDA__VDPAU">3.29. VDPAU Interoperability</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="structCUDA__ARRAY3D__DESCRIPTOR.html#structCUDA__ARRAY3D__DESCRIPTOR">4.1. CUDA_ARRAY3D_DESCRIPTOR</a></div>
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<div class="section-link"><a href="structCUDA__ARRAY__DESCRIPTOR.html#structCUDA__ARRAY__DESCRIPTOR">4.2. CUDA_ARRAY_DESCRIPTOR</a></div>
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<div class="section-link"><a href="structCUDA__MEMCPY2D.html#structCUDA__MEMCPY2D">4.3. CUDA_MEMCPY2D</a></div>
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<div class="section-link"><a href="structCUDA__MEMCPY3D.html#structCUDA__MEMCPY3D">4.4. CUDA_MEMCPY3D</a></div>
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<div class="section-link"><a href="structCUDA__MEMCPY3D__PEER.html#structCUDA__MEMCPY3D__PEER">4.5. CUDA_MEMCPY3D_PEER</a></div>
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<div class="section-link"><a href="structCUDA__POINTER__ATTRIBUTE__P2P__TOKENS.html#structCUDA__POINTER__ATTRIBUTE__P2P__TOKENS">4.6. CUDA_POINTER_ATTRIBUTE_P2P_TOKENS</a></div>
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<div class="section-link"><a href="structCUDA__RESOURCE__DESC.html#structCUDA__RESOURCE__DESC">4.7. CUDA_RESOURCE_DESC</a></div>
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<div class="section-link"><a href="structCUDA__RESOURCE__VIEW__DESC.html#structCUDA__RESOURCE__VIEW__DESC">4.8. CUDA_RESOURCE_VIEW_DESC</a></div>
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<div class="section-link"><a href="structCUDA__TEXTURE__DESC.html#structCUDA__TEXTURE__DESC">4.9. CUDA_TEXTURE_DESC</a></div>
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<div class="section-link"><a href="structCUdevprop.html#structCUdevprop">4.10. CUdevprop</a></div>
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<div class="section-link"><a href="structCUipcEventHandle.html#structCUipcEventHandle">4.11. CUipcEventHandle</a></div>
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<div class="section-link"><a href="structCUipcMemHandle.html#structCUipcMemHandle">4.12. CUipcMemHandle</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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