配置YOLOv5-1.0版本，自己调试cpu版本环境时出现的问题

一：下载安装包先是安装了cpu版本pytorch1.4.0，链接地址如下：

https://download.pytorch.org/whl/torch_stable.html 

下载相应版本的即可，如我的电脑anaconda下的yolov5的虚拟环境python=3.6，电脑时64位的，故下载时选了

torch-1.4.0+cpu-cp36-cp36m-win_amd64.whl

然后在激活环境后，切换到这个安装包所在的文件下，然后执行pip安装即可

pip install  torch-1.4.0+cpu-cp36-cp36m-win_amd64.whl

 二：当我以同样的方式安装torchvision时出现了问题，

pip install torchvision-0.5.0+cpu-cp36-cp36m-win_amd64.whl

报错

 ERROR: Exception:
Traceback (most recent call last):
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_internal\cli\base_command.py", line 173, in _main
    status = self.run(options, args)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_internal\cli\req_command.py", line 203, in wrapper
    return func(self, options, args)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_internal\commands\install.py", line 316, in run
    reqs, check_supported_wheels=not options.target_dir
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_internal\resolution\resolvelib\resolver.py", line 95, in resolve
    collected.requirements, max_rounds=try_to_avoid_resolution_too_deep
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_vendor\resolvelib\resolvers.py", line 472, in resolve
    state = resolution.resolve(requirements, max_rounds=max_rounds)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_vendor\resolvelib\resolvers.py", line 341, in resolve
    self._add_to_criteria(self.state.criteria, r, parent=None)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_vendor\resolvelib\resolvers.py", line 172, in _add_to_criteria
    if not criterion.candidates:
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_vendor\resolvelib\structs.py", line 151, in __bool__
    return bool(self._sequence)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_internal\resolution\resolvelib\found_candidates.py", line 140, in __bool__
    return any(self)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_internal\resolution\resolvelib\found_candidates.py", line 128, in <genexpr>
    return (c for c in iterator if id(c) not in self._incompatible_ids)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_internal\resolution\resolvelib\found_candidates.py", line 29, in _iter_built
    for version, func in infos:
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_internal\resolution\resolvelib\factory.py", line 275, in iter_index_candidate_infos
    hashes=hashes,
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_internal\index\package_finder.py", line 851, in find_best_candidate
    candidates = self.find_all_candidates(project_name)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_internal\index\package_finder.py", line 798, in find_all_candidates
    page_candidates = list(page_candidates_it)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_internal\index\sources.py", line 134, in page_candidates
    yield from self._candidates_from_page(self._link)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_internal\index\package_finder.py", line 758, in process_project_url
    html_page = self._link_collector.fetch_page(project_url)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_internal\index\collector.py", line 490, in fetch_page
    return _get_html_page(location, session=self.session)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_internal\index\collector.py", line 400, in _get_html_page
    resp = _get_html_response(url, session=session)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_internal\index\collector.py", line 132, in _get_html_response
    "Cache-Control": "max-age=0",
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_vendor\requests\sessions.py", line 555, in get
    return self.request('GET', url, **kwargs)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_internal\network\session.py", line 454, in request
    return super().request(method, url, *args, **kwargs)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_vendor\requests\sessions.py", line 542, in request
    resp = self.send(prep, **send_kwargs)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_vendor\requests\sessions.py", line 655, in send
    r = adapter.send(request, **kwargs)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_vendor\cachecontrol\adapter.py", line 53, in send
    resp = super(CacheControlAdapter, self).send(request, **kw)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_vendor\requests\adapters.py", line 449, in send
    timeout=timeout
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_vendor\urllib3\connectionpool.py", line 696, in urlopen
    self._prepare_proxy(conn)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_vendor\urllib3\connectionpool.py", line 964, in _prepare_proxy
    conn.connect()
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_vendor\urllib3\connection.py", line 359, in connect
    conn = self._connect_tls_proxy(hostname, conn)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_vendor\urllib3\connection.py", line 506, in _connect_tls_proxy
    ssl_context=ssl_context,
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_vendor\urllib3\util\ssl_.py", line 453, in ssl_wrap_socket
    ssl_sock = _ssl_wrap_socket_impl(sock, context, tls_in_tls)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\site-packages\pip\_vendor\urllib3\util\ssl_.py", line 495, in _ssl_wrap_socket_impl
    return ssl_context.wrap_socket(sock)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\ssl.py", line 407, in wrap_socket
    _context=self, _session=session)
  File "C:\ProgramData\Anaconda3\envs\yolov5\lib\ssl.py", line 773, in __init__
    raise ValueError("check_hostname requires server_hostname")
ValueError: check_hostname requires server_hostname

看了网上说是网络问题， 但是我按着别人的方法没有解决，于是我就换了一个版本

安装0.6版本的torchvision，

结果出现一个新的警告，我看好像需要添加豆瓣源把相应的依赖库装上吧。 

WARNING: The repository located at pypi.douban.com is not a trusted or secure host and is being ignored. If this repository is available via HTTPS we recommend you use HTTPS instead, otherwise you may silence this warning and allow it anyway with '--trusted-host pypi.douban.com'.
ERROR: Could not find a version that satisfies the requirement numpy (from torchvision) (from versions: none)
ERROR: No matching distribution found for numpy
WARNING: The repository located at pypi.douban.com is not a trusted or secure host and is being ignored. If this repository is available via HTTPS we recommend you use HTTPS instead, otherwise you may silence this warning and allow it anyway with '--trusted-host pypi.douban.com'.

 于是我把命令改为

pip install torchvision-0.6.0+cpu-cp36-cp36m-win_amd64.whl --trusted-host pypi.douban.com

 解决。