R** move cmake installation into env_create.sh

[guru-desh]

I had a previous PR for this, however, I had made some edits to my fork that closed the pull request and added commits from another feature I was working on. I guess that's a reminder to me to make new branches in git 😄 . Apologies for a duplicate PR. Here's the original description:

This PR simplifies the build setup process by installing cmake via conda.

Current Behavior:

In the build.sh script, this if statement exists:

if [ -z "`which cmake`" ] || [ "`which cmake`" = "cmake not found" ]; then
  conda install cmake -y
fi

If cmake does not exist on the machine used to build coremltools, then cmake will be installed via conda. BUILDING.md states that the user needs to install cmake. However, if the build.sh script already installs cmake then the following refactor can be done:

1. Install cmake by default into the conda environment
2. Remove the requirement for the user to install cmake outside of the coremltools build

New Behavior:

1. This env_create.sh script installs cmake via the anaconda channel.
2. The CMake requirement is removed from the requirements section (the user who builds the project no longer needs to install cmake themselves)

This refactor makes it so that the user no longer needs to install cmake before building coremltools (as the build itself will install cmake via conda)

Checks

Running ./scripts/build.sh --python=3.8 created a working build for me locally, but I'm not sure how to run the GitLab CI job. Could I get some help on that? Thanks in advance 😄

[TobyRoseman]

The change looks good. I've kicked off a CI run: https://gitlab.com/coremltools1/coremltools/-/pipelines/1544298967

[guru-desh]

Thanks for the CI run! Here's a link to the previous PR that I forgot to link: #2379

In that previous PR, there were some questions that had come up. I will link my response below:

could you please elaborate on the motivation for "move conda install to env_create.sh" change?

This was a pure refactoring change. In build.sh, I saw that the majority of the steps build.sh are build-specific steps like setting up the cmake commands and running make, and the conda install -y cmake command doesn't seem like a build-related step but more of an environment config step. This is why I moved it to env_create.sh.

In addition, if conda install -y cmake was in build.sh, then dependency management becomes harder as the dependency of cmake is specified not in env_create.sh but in build.sh, which should not add environment dependencies.

Imho I would prefer to keep it in build.sh, because "install after env got created" will work for env-tweaking cases, e.g. Rosetta

Could you explain what "env-tweaking cases" are? Why can't the env-tweaking cases be done in the env_create.sh script?

[TobyRoseman]

@YifanShenSZ - can respond to the above questions? I think since this change only installs cmake if it isn't already installed, it shouldn't matter which script installs it.

[guru-desh]

I think since this change only installs cmake if it isn't already installed, it shouldn't matter which script installs it.

I would like to clarify this. The change installs cmake into the conda environment regardless of whether cmake already exists on the host machine or not. This means that when the environment is activated and a build is run, then the cmake inside the conda environment will be used.

[guru-desh]

@TobyRoseman any update on this?