[reland] Remove balance and devices parameter from Pipe.

[pritamdamania87]

Stack from ghstack:

• Improve documentation for pipeline parallelism. #48638 Improve documentation for pipeline parallelism.
• Cleanup APIs for pipeline parallelism. #48630 Cleanup APIs for pipeline parallelism.
• Test pipeline parallelism works with DDP. #48470 Test pipeline parallelism works with DDP.
• Update pipeline API to accept arbitrary sequence of Tensors and not just Tuple #48467 Update pipeline API to accept arbitrary sequence of Tensors and not just Tuple
• Modify Pipe to return an RRef. #47829 Modify Pipe to return an RRef.
• [reland] Remove balance and devices parameter from Pipe. #48432 [reland] Remove balance and devices parameter from Pipe.

As per our design in #44827,
changign the API such that the user places modules on appropriate devices
instead of having a balance and devices parameter that decides this.

This design allows us to use RemoteModule in the future.

Differential Revision: D25172970

[dr-ci]

💊 CI failures summary and remediations

As of commit 4b41445 (more details on the Dr. CI page):

---

• 3/4 failures introduced in this PR
• 1/4 broken upstream at merge base 5bb2a87 on Nov 30 from 7:48am to 3:47pm PDT (15 commits; 5bb2a87 - d74f2d2)

---

3 failures not recognized by patterns:

Job	Step	Action
pytorch_linux_xenial_py3_clang5_asan_build	Build	🔁 rerun
pytorch_libtorch_linux_xenial_cuda11_1_cudnn8_py3_gcc7_build	Set Up CI Environment After attach_workspace	🔁 rerun
pytorch-linux-xenial-py3-clang5-android-ndk-r19c-gradle-custom-build-single	Set Up CI Environment After attach_workspace	🔁 rerun

---

🚧 1 fixed upstream failure:

These were probably caused by upstream breakages that were already fixed.

Please rebase on the viable/strict branch (expand for instructions)

If your commit is newer than viable/strict, you can try basing on an older, stable commit:

git fetch https://github.com/pytorch/pytorch viable/strict
git rebase --onto FETCH_HEAD $(git merge-base origin/master HEAD)

If your commit is older than viable/strict:

git fetch https://github.com/pytorch/pytorch viable/strict
git rebase FETCH_HEAD

Check out the recency history of this "viable master" tracking branch.

• pytorch_bazel_build on Nov 30 from 7:48am to 3:47pm PDT (15 commits; 5bb2a87 - d74f2d2)
  • 🔁 rerun

---

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This comment has been revised 13 times.

[codecov]

Codecov Report

Merging #48432 (c28a7dd) into gh/pritamdamania87/182/base (5bb2a87) will decrease coverage by 0.14%.
The diff coverage is 61.76%.

@@                       Coverage Diff                       @@
##           gh/pritamdamania87/182/base   #48432      +/-   ##
===============================================================
- Coverage                        80.91%   80.76%   -0.15%     
===============================================================
  Files                             1855     1856       +1     
  Lines                           200241   200130     -111     
===============================================================
- Hits                            162023   161639     -384     
- Misses                           38218    38491     +273     

[pritamdamania87]

This message matching has changed and was failing lint earlier to the escape sequence \(

[facebook-github-bot]

This pull request has been merged in 7c73fda.

[facebook-github-bot]

This pull request has been merged in 7c73fda.