开发环境
UE4.25
lipengzha
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Setup 多线程数加速下载

在下载 UE4 的源码之后，需要先执行 Setup.bat 下载依赖才可以开始生成 VS 项目文件以及编译。
但是国内的网络环境又极差，默认的 Setup.bat 是没有指定线程数量的（Setup.bat只给 GitDenpencies 传递了 --prompt 参数）。

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@echo off
setlocal
pushd %~dp0

rem Figure out if we should append the -prompt argument
set PROMPT_ARGUMENT=
for %%P in (%*) do if /I "%%P" == "--prompt" goto no_prompt_argument
for %%P in (%*) do if /I "%%P" == "--force" goto no_prompt_argument
set PROMPT_ARGUMENT=--prompt
:no_prompt_argument

rem Sync the dependencies...
.\Engine\Binaries\DotNET\GitDependencies.exe %PROMPT_ARGUMENT% %*
if ERRORLEVEL 1 goto error

rem Setup the git hooks...
if not exist .git\hooks goto no_git_hooks_directory
echo Registering git hooks...
echo #!/bin/sh >.git\hooks\post-checkout
echo Engine/Binaries/DotNET/GitDependencies.exe %* >>.git\hooks\post-checkout
echo #!/bin/sh >.git\hooks\post-merge
echo Engine/Binaries/DotNET/GitDependencies.exe %* >>.git\hooks\post-merge
:no_git_hooks_directory

rem Install prerequisites...
echo Installing prerequisites...
start /wait Engine\Extras\Redist\en-us\UE4PrereqSetup_x64.exe /quiet

rem Register the engine installation...
if not exist .\Engine\Binaries\Win64\UnrealVersionSelector-Win64-Shipping.exe goto :no_unreal_version_selector
.\Engine\Binaries\Win64\UnrealVersionSelector-Win64-Shipping.exe /register
:no_unreal_version_selector

rem Done!
goto :EOF

rem Error happened. Wait for a keypress before quitting.
:error
pause

GitDependencies.exe支持的参数为：

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Usage:
   GitDependencies [options]

Options:
   --all                         Sync all folders
   --include=<X>                 Include binaries in folders called <X>
   --exclude=<X>                 Exclude binaries in folders called <X>
   --prompt                      Prompt before overwriting modified files
   --force                       Always overwrite modified files
   --root=<PATH>                 Set the repository directory to be sync
   --threads=<N>                 Use N threads when downloading new files
   --dry-run                     Print a list of outdated files and exit
   --max-retries                 Override maximum number of retries per file
   --proxy=<user:password@url>   Sets the HTTP proxy address and credentials
   --cache=<PATH>                Specifies a custom path for the download cache
   --cache-size-multiplier=<N>   Cache size as multiplier of current download
   --cache-days=<N>              Number of days to keep entries in the cache
   --no-cache                    Disable caching of downloaded files

Detected settings:
   Excluded folders: Mac, Android, Linux
   Proxy server: none
   Download cache: E:\UnrealEngine\EngineSource\UE_4.21_Source\.git\ue4-gitdeps

Default arguments can be set through the UE4_GITDEPS_ARGS environment variable.

所以我们可以将 Setup.bat 中的变量 PROMPT_ARGUMENT 增加上指定的线程数即可（N 替换为数字）：

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set PROMPT_ARGUMENT=--prompt --threads=N

我一般开 8 个线程，基本可以跑 2-3M/s…