Trying to install pytorch 1.2 with cudatoolkit 9.2, with conda install pytorch==1.2.0 torchvision==0.4.0 cudatoolkit=9.2 -c pytorch. Output below. It seems that cudatoolkit 9.2 is not available in any conda channel…
Collecting package metadata (current_repodata.json): done
Solving environment: failed with initial frozen solve. Retrying with flexible solve.
Collecting package metadata (repodata.json): done
Solving environment: failed with initial frozen solve. Retrying with flexible solve.

PackagesNotFoundError: The following packages are not available from current channels:

  - cudatoolkit=9.2

Current channels:

  - https://conda.anaconda.org/pytorch/win-64
  - https://conda.anaconda.org/pytorch/noarch
  - https://conda.anaconda.org/conda-forge/win-64
  - https://conda.anaconda.org/conda-forge/noarch
  - https://conda.anaconda.org/ostrokach-forge/win-64
  - https://conda.anaconda.org/ostrokach-forge/noarch
  - https://conda.anaconda.org/anaconda-fusion/win-64
  - https://conda.anaconda.org/anaconda-fusion/noarch
  - https://repo.anaconda.com/pkgs/main/win-64
  - https://repo.anaconda.com/pkgs/main/noarch
  - https://repo.anaconda.com/pkgs/r/win-64
  - https://repo.anaconda.com/pkgs/r/noarch
  - https://repo.anaconda.com/pkgs/msys2/win-64
  - https://repo.anaconda.com/pkgs/msys2/noarch

To search for alternate channels that may provide the conda package you're
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    https://anaconda.org

and use the search bar at the top of the page.