Difference between revisions of "Streams and Multi-GPU using CUVI"
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gout->height = gout->height / streamCount; | gout->height = gout->height / streamCount; | ||
//Creating streams | |||
CuviStream **streams = new CuviStream*[streamCount]; | CuviStream **streams = new CuviStream*[streamCount]; | ||
for(int i=0; i<streamCount; i++) | for(int i=0; i<streamCount; i++) | ||
cuviCreateStream(&streams[i]); | cuviCreateStream(&streams[i]); | ||
//Chunks sizes for streams | |||
//gpuChunk and hostChunk are mostly different because their pitch is different | |||
size_t gpuChunk = gimg->height * gimg->pitch, | size_t gpuChunk = gimg->height * gimg->pitch, | ||
gpuOutChunk = gimg->height * gout->pitch, | gpuOutChunk = gimg->height * gout->pitch, | ||
Line 64: | Line 61: | ||
hostOutChunk = gimg->height * host_out->widthStep; | hostOutChunk = gimg->height * host_out->widthStep; | ||
//Uploading image data to GPU in streams | |||
for(int i=0; i<streamCount; i++) | for(int i=0; i<streamCount; i++) | ||
inputImage->upload(gimg->data + i*gpuChunk, cpu_ptr + i*hostChunk, host_img->widthStep,streams[i]); | inputImage->upload(gimg->data + i*gpuChunk, cpu_ptr + i*hostChunk, host_img->widthStep,streams[i]); | ||
//Function call on each stream | |||
for(int i=0; i<streamCount; i++) | for(int i=0; i<streamCount; i++) | ||
cuvi::colorOperations::RGB2Gray(gimg + i*gpuChunk, gout + i*gpuOutChunk, streams[i]); | cuvi::colorOperations::RGB2Gray(gimg + i*gpuChunk, gout + i*gpuOutChunk, streams[i]); | ||
//Downloading resultant data back to host in streams | |||
for(int i=0; i<streamCount; i++) | for(int i=0; i<streamCount; i++) | ||
gout->download(cpu_out_ptr + i*hostOutChunk , gout + i*gpuOutChunk, host_out->widthStep, streams[i]); | gout->download(cpu_out_ptr + i*hostOutChunk , gout + i*gpuOutChunk, host_out->widthStep, streams[i]); | ||
//Destroying streams | |||
for(int i=0; i<streamCount; i++) | for(int i=0; i<streamCount; i++) | ||
cuviDestroyStream(&(streams[i])); | cuviDestroyStream(&(streams[i])); | ||
//Freeing GPU memory | |||
delete gimg; | delete gimg; | ||
delete gout; | delete gout; |
Revision as of 15:31, 4 May 2012
Using Streams with CUVI
CUVI framework provides a way to use streams with minimal coding effort. Each function call in CUVI takes an optional parameter to specify the stream on which it should run. The code below shows how a simple function call of CUVI can be divided into streaming calls on GPU. For most of the cases this will result in better performance as copying image data to GPU and processing that data on GPU happens simultaneously.
CUVI example
In this example we use CUVI's RGB2Gray function from Color Operations module on a full HD input image
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Same example with Streams
Streams greatly improve performance of your application by hiding data processing time in data copying time. Instead of waiting for the complete image to be copied on GPU before processing, streaming enables processing the data as it arrives on GPU. Here's how you can use streaming in your application using CUVI:
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