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OpenCV GPU without compiling ?

asked 2020-09-14 10:14:12 -0600

Kreace gravatar image

Hello, i'm pretty new to OpenCV. I would like to use my GPU (Nvidia Geforce GTX 970) to run a Yolov3 (and 4) Neural Net. It works without any problems with my CPU but as you may already understand it's slow.

So I changed theses two lines in my code : (python3 script)

1- I understood that "setPreferableTarget" set the hardware on which the neural network will be compute but what does "setPreferableBackend" do ? What is a Backend?

I tried to run my script and I get this warning :

[ WARN:0] global ../modules/dnn/src/dnn.cpp (1363) setUpNet DNN module was not built with CUDA backend; switching to CPU

2- I understood that means that OpenCV wasn't install with CUDA support, am I right here?

3- Isn't there any other way to install OpenCV with CUDA other than compile it from source? I installed OpenCV with sudo apt-get install libopencv-dev so i thought that maybe there is a way to do it like that, i don't know.

Thank you for taking the time to read me and thank you in advance for answering me, tell me if you need some additional information.

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answered 2020-09-15 18:57:23 -0600

heavyswat gravatar image

I just compiled OpenCV 4.5.0-pre with CUDA 11.0 on Ubuntu 20.04.

I have followed the official NVIDIA CUDA 11.0 with deb(local). It's so much easier than the run file. And please use GitHub openCV 4.5.0-pre so it is compatible with CUDA 11.0

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I'm trying to get a clean new installation with Ubuntu 20.04 I have install CUDA 11.0 like you but I don't know how to download opencv 4.5.0-pre, I used :

git clone

but the latest version i can find is 4.4.0

Kreace gravatar imageKreace ( 2020-09-17 07:48:54 -0600 )edit

It worked fine with opencv 4.4.0!

Kreace gravatar imageKreace ( 2020-09-18 03:03:46 -0600 )edit

answered 2020-09-15 03:16:48 -0600

Naser gravatar image

updated 2020-09-15 03:26:07 -0600

You need to build opencv with cuda support from source. You can find a nice solution in this link : build opencv with cuda support. I did it on my own PC without any problem.

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Yes i found it too but it's for Ubuntu 18.04, I'm using Ubuntu 20.04 so i don't know if it's up to date

Kreace gravatar imageKreace ( 2020-09-15 03:43:57 -0600 )edit

I tested it on ubuntu 20.04 but there is some issues in cuda toolkit installing in ubuntu 20.04. So i couldn't configure it. But works fine in ubuntu 18.04. Why not use ubutnu 18.04 ?

Naser gravatar imageNaser ( 2020-09-15 06:30:30 -0600 )edit

I wanted to use ROS2 in my program so I decided to take the latest version (ROS2 Foxy Fitzroy) and they provide binary packages for Ubuntu 20.04 so i took it accordingly

Kreace gravatar imageKreace ( 2020-09-15 09:54:49 -0600 )edit

answered 2020-09-15 01:35:15 -0600

berak gravatar image

you won'r get any gpu support using prebuilt binaries from any package manager.

you'll have to install the CUDA sdk, get the opencv (github) and opencv_contrib src code, and build from that, using cmake

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Asked: 2020-09-14 10:13:35 -0600

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Last updated: Sep 15 '20