[Docs] Update install tutorials. (#854)

* [Docs] Update install tutorials.

* [Docs] Improve dataset docs

* Add option to show the results in demo.

* fix typo

demo/image_demo.py

@@ -1,6 +1,8 @@
 # Copyright (c) OpenMMLab. All rights reserved.
 from argparse import ArgumentParser
 
+import mmcv
+
 from mmcls.apis import inference_model, init_model, show_result_pyplot
 
 
@@ -9,6 +11,10 @@ def main():
     parser.add_argument('img', help='Image file')
     parser.add_argument('config', help='Config file')
     parser.add_argument('checkpoint', help='Checkpoint file')
+    parser.add_argument(
+        '--show',
+        action='store_true',
+        help='Whether to show the predict results by matplotlib.')
     parser.add_argument(
         '--device', default='cuda:0', help='Device used for inference')
     args = parser.parse_args()
@@ -18,7 +24,9 @@ def main():
     # test a single image
     result = inference_model(model, args.img)
     # show the results
-    show_result_pyplot(model, args.img, result)
+    print(mmcv.dump(result, file_format='json', indent=4))
+    if args.show:
+        show_result_pyplot(model, args.img, result)
 
 
 if __name__ == '__main__':

docs/en/faq.md

@@ -0,0 +1,82 @@
+# Frequently Asked Questions
+
+We list some common troubles faced by many users and their corresponding
+solutions here. Feel free to enrich the list if you find any frequent issues
+and have ways to help others to solve them. If the contents here do not cover
+your issue, please create an issue using the
+[provided templates](https://github.com/open-mmlab/mmclassification/issues/new/choose)
+and make sure you fill in all required information in the template.
+
+## Installation
+
+- Compatibility issue between MMCV and MMClassification; "AssertionError:
+  MMCV==xxx is used but incompatible. Please install mmcv>=xxx, <=xxx."
+
+  Compatible MMClassification and MMCV versions are shown as below. Please
+  choose the correct version of MMCV to avoid installation issues.
+
+  | MMClassification version |     MMCV version      |
+  |:------------------------:|:---------------------:|
+  | dev                      | mmcv>=1.5.0, <1.6.0   |
+  | 0.23.0 (master)          | mmcv>=1.4.2, <1.6.0   |
+  | 0.22.1                   | mmcv>=1.4.2, <1.6.0   |
+  | 0.21.0                   | mmcv>=1.4.2, <=1.5.0  |
+  | 0.20.1                   | mmcv>=1.4.2, <=1.5.0  |
+  | 0.19.0                   | mmcv>=1.3.16, <=1.5.0 |
+  | 0.18.0                   | mmcv>=1.3.16, <=1.5.0 |
+  | 0.17.0                   | mmcv>=1.3.8, <=1.5.0  |
+  | 0.16.0                   | mmcv>=1.3.8, <=1.5.0  |
+  | 0.15.0                   | mmcv>=1.3.8, <=1.5.0  |
+  | 0.15.0                   | mmcv>=1.3.8, <=1.5.0  |
+  | 0.14.0                   | mmcv>=1.3.8, <=1.5.0  |
+  | 0.13.0                   | mmcv>=1.3.8, <=1.5.0  |
+  | 0.12.0                   | mmcv>=1.3.1, <=1.5.0  |
+  | 0.11.1                   | mmcv>=1.3.1, <=1.5.0  |
+  | 0.11.0                   | mmcv>=1.3.0           |
+  | 0.10.0                   | mmcv>=1.3.0           |
+  | 0.9.0                    | mmcv>=1.1.4           |
+  | 0.8.0                    | mmcv>=1.1.4           |
+  | 0.7.0                    | mmcv>=1.1.4           |
+  | 0.6.0                    | mmcv>=1.1.4           |
+
+  ```{note}
+  Since the `dev` branch is under frequent development, the MMCV
+  version dependency may be inaccurate. If you encounter problems when using
+  the `dev` branch, please try to update MMCV to the latest version.
+  ```
+
+- Using Albumentations
+
+  If you would like to use `albumentations`, we suggest using `pip install -r requirements/albu.txt` or
+  `pip install -U albumentations --no-binary qudida,albumentations`.
+
+  If you simply use `pip install albumentations>=0.3.2`, it will install `opencv-python-headless` simultaneously
+  (even though you have already installed `opencv-python`). Please refer to the
+  [official documentation](https://albumentations.ai/docs/getting_started/installation/#note-on-opencv-dependencies)
+  for details.
+
+## Coding
+
+- Do I need to reinstall mmcls after some code modifications?
+
+  If you follow [the best practice](install.md) and install mmcls from source,
+  any local modifications made to the code will take effect without
+  reinstallation.
+
+- How to develop with multiple MMClassification versions?
+
+  Generally speaking, we recommend to use different virtual environments to
+  manage MMClassification in different working directories. However, you
+  can also use the same environment to develop MMClassification in different
+  folders, like mmcls-0.21, mmcls-0.23. When you run the train or test shell script,
+  it will adopt the mmcls package in the current folder. And when you run other Python
+  script, you can also add ``PYTHONPATH=`pwd` `` at the beginning of your command
+  to use the package in the current folder.
+
+  Conversely, to use the default MMClassification installed in the environment
+  rather than the one you are working with, you can remove the following line
+  in those shell scripts:
+
+  ```shell
+  PYTHONPATH="$(dirname $0)/..":$PYTHONPATH
+  ```

docs/en/index.rst

@@ -72,9 +72,11 @@ You can switch between Chinese and English documentation in the lower-left corne
 
 .. toctree::
    :maxdepth: 1
-   :caption: Changelog
+   :caption: Notes
 
    changelog.md
+   compatibility.md
+   faq.md
 
 .. toctree::
    :caption: Language Switch