随着网络越来约复杂，训练难度越来越大，有条件的可以采用GPU进行学习。本文介绍如何在GPU环境下使用TensorFlow.NET。
TensorFlow.NET使用GPU非常的简单，代码不用做任何修改，更换一个依赖库即可，程序是否能运行成功主要看环境是否安装正确，这篇文章重点介绍的也就是环境的安装了。
CUDA和cuDNN的安装都比较容易，重点是要装对版本。
1、确认安装版本
首先电脑得有一块NVIDIA的显卡！
在桌面右键选择NVIDIA控制面板，在程序左下角点击 ：系统信息。
首先要确认显卡CUDA的版本，我的是10.1，实际安装时要根据自己的环境来。
根据显卡CUDA版本，需要安装对应的CUDA Toolkit和cuDNN的包，同时也要引用对应版本的TensorFlow_gpu运行库。
这是TensorFlow官方网站提供的一个对应关系。
2、安装CUDA Toolkit
安装包下载地址：CUDA Toolkit 11.5 Update 1 Downloads | NVIDIA Developer
由于不可描述的原因，网站打开很慢，需要有一定的耐心。
我下载的程序为：cuda_10.1.243_win10_network.exe，要保证前两个版本号和本机显卡的CUDA版本一致，最后一位影响不大。
只要选对版本，安装就没有问题了，基本一路下一步就可以了。
3、安装cuDNN
在NVIDIA网站搜索cuDNN即可找到下载地址，同样要注意版本。
我下载的文件为：cudnn-10.1-windows10-x64-v8.0.5.39.zip
从文件名可以看出，该软件版本为8.0，对应的CUDA版本为10.1，这点和TensonFlow网站上说的不完全一致，但实测可以使用。
注意cuDNN软件不需要安装，只要解压到指定目录即可。
假设CUDA安装目录为：C:\Program Files\NVIDIA GPU Computing Toolkit\CUDA\V10.1
解压后的文件包括：bin、inclue、lib三个文件夹，和CUDA安装目录下的三个同名文件夹合并即可。
【我怀疑随便解压到什么位置，只要把路径加入到path里即可，但我没有测试过。】
4、更换依赖库
本系列第一篇就介绍过一个TensorFlow,NET项目的依赖库如下：
如果需要采用GPU学习，更改其中的一个库如下即可。
需要注意运行库的版本。我的GPU最高支持2.3
如果此时你的运行环境没有具备，程序运行时会弹出警告，并自动切换到CPU进行计算。
5、调试
如果环境没有安装成功，程序运行会打印下列信息：
2021-08-29 09:46:26.631756: W tensorflow/stream_executor/platform/default/dso_loader.cc:64] Could not load dynamic library 'cudart64_110.dll'; dlerror: cudart64_110.dll not found 2021-08-29 09:46:26.633225: I tensorflow/stream_executor/cuda/cudart_stub.cc:29] Ignore above cudart dlerror if you do not have a GPU set up on your machine. 2021-08-29 09:46:27.323608: I tensorflow/core/platform/cpu_feature_guard.cc:142] This TensorFlow binary is optimized with oneAPI Deep Neural Network Library (oneDNN) to use the following CPU instructions in performance-critical operations: AVX2 To enable them in other operations, rebuild TensorFlow with the appropriate compiler flags. 2021-08-29 09:46:27.993386: W tensorflow/stream_executor/platform/default/dso_loader.cc:64] Could not load dynamic library 'cudart64_110.dll'; dlerror: cudart64_110.dll not found 2021-08-29 09:46:27.994493: W tensorflow/stream_executor/platform/default/dso_loader.cc:64] Could not load dynamic library 'cublas64_11.dll'; dlerror: cublas64_11.dll not found 2021-08-29 09:46:27.997410: W tensorflow/stream_executor/platform/default/dso_loader.cc:64] Could not load dynamic library 'cufft64_10.dll'; dlerror: cufft64_10.dll not found 2021-08-29 09:46:27.998498: W tensorflow/stream_executor/platform/default/dso_loader.cc:64] Could not load dynamic library 'curand64_10.dll'; dlerror: curand64_10.dll not found 2021-08-29 09:46:27.999403: W tensorflow/stream_executor/platform/default/dso_loader.cc:64] Could not load dynamic library 'cusolver64_11.dll'; dlerror: cusolver64_11.dll not found 2021-08-29 09:46:28.000402: W tensorflow/stream_executor/platform/default/dso_loader.cc:64] Could not load dynamic library 'cusparse64_11.dll'; dlerror: cusparse64_11.dll not found 2021-08-29 09:46:28.001807: W tensorflow/stream_executor/platform/default/dso_loader.cc:64] Could not load dynamic library 'cudnn64_8.dll'; dlerror: cudnn64_8.dll not found 2021-08-29 09:46:28.001917: W tensorflow/core/common_runtime/gpu/gpu_device.cc:1835] Cannot dlopen some GPU libraries. Please make sure the missing libraries mentioned above are installed properly if you would like to use GPU. Follow the guide at https://www.tensorflow.org/install/gpu for how to download and setup the required libraries for your platform. Skipping registering GPU devices...
关键字：Could not load dynamic library
如果环境安装成功，则显示如下：
2021-08-29 09:46:26.631756: W tensorflow/stream_executor/platform/default/dso_loader.cc:64] Could not load dynamic library 'cudart64_110.dll'; dlerror: cudart64_110.dll not found 2021-08-29 09:46:26.633225: I tensorflow/stream_executor/cuda/cudart_stub.cc:29] Ignore above cudart dlerror if you do not have a GPU set up on your machine. 2021-08-29 09:46:27.323608: I tensorflow/core/platform/cpu_feature_guard.cc:142] This TensorFlow binary is optimized with oneAPI Deep Neural Network Library (oneDNN) to use the following CPU instructions in performance-critical operations: AVX2 To enable them in other operations, rebuild TensorFlow with the appropriate compiler flags. 2021-08-29 09:46:27.993386: W tensorflow/stream_executor/platform/default/dso_loader.cc:64] Could not load dynamic library 'cudart64_110.dll'; dlerror: cudart64_110.dll not found 2021-08-29 09:46:27.994493: W tensorflow/stream_executor/platform/default/dso_loader.cc:64] Could not load dynamic library 'cublas64_11.dll'; dlerror: cublas64_11.dll not found 2021-08-29 09:46:27.997410: W tensorflow/stream_executor/platform/default/dso_loader.cc:64] Could not load dynamic library 'cufft64_10.dll'; dlerror: cufft64_10.dll not found 2021-08-29 09:46:27.998498: W tensorflow/stream_executor/platform/default/dso_loader.cc:64] Could not load dynamic library 'curand64_10.dll'; dlerror: curand64_10.dll not found 2021-08-29 09:46:27.999403: W tensorflow/stream_executor/platform/default/dso_loader.cc:64] Could not load dynamic library 'cusolver64_11.dll'; dlerror: cusolver64_11.dll not found 2021-08-29 09:46:28.000402: W tensorflow/stream_executor/platform/default/dso_loader.cc:64] Could not load dynamic library 'cusparse64_11.dll'; dlerror: cusparse64_11.dll not found 2021-08-29 09:46:28.001807: W tensorflow/stream_executor/platform/default/dso_loader.cc:64] Could not load dynamic library 'cudnn64_8.dll'; dlerror: cudnn64_8.dll not found 2021-08-29 09:46:28.001917: W tensorflow/core/common_runtime/gpu/gpu_device.cc:1835] Cannot dlopen some GPU libraries. Please make sure the missing libraries mentioned above are installed properly if you would like to use GPU. Follow the guide at https://www.tensorflow.org/install/gpu for how to download and setup the required libraries for your platform. Skipping registering GPU devices...
关键字：Successfully opened dynamic library
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