Load correct libtpu for pytorch & jax.

It turns out jax & pytorch are incompatible (require different libtpu
versions). In order to support importing EITHER of them (but not both)
we will swap in the correct libtpu during import (by monkey-patching the
import code for both).

http:https://b/213335159

tpu/Dockerfile

@@ -1,8 +1,6 @@
 ARG BASE_IMAGE_TAG
-ARG LIBTPU_IMAGE_TAG
 ARG TENSORFLOW_VERSION
 
-FROM gcr.io/cloud-tpu-v2-images/libtpu:${LIBTPU_IMAGE_TAG} as libtpu
 FROM gcr.io/kaggle-images/python-tpu-tensorflow-whl:python-${BASE_IMAGE_TAG}-${TENSORFLOW_VERSION} AS tensorflow_whl
 FROM gcr.io/kaggle-images/python:${BASE_IMAGE_TAG}
 
@@ -12,20 +10,29 @@ ARG TORCH_VERSION
 
 ENV ISTPUVM=1
 
-COPY --from=libtpu /libtpu.so /lib
-
 COPY --from=tensorflow_whl /tmp/tensorflow_pkg/tensorflow*.whl /tmp/tensorflow_pkg/
 RUN pip install /tmp/tensorflow_pkg/tensorflow*.whl && \
  rm -rf /tmp/tensorflow_pkg && \
  /tmp/clean-layer.sh
 
+# LIBTPU installed here:
+ENV DEFAULT_LIBTPU=/opt/conda/lib/python3.7/site-packages/libtpu/libtpu.so
+ENV PYTORCH_LIBTPU=/opt/conda/lib/python3.7/site-packages/libtpu/torch-libtpu.so
+ENV JAX_LIBTPU=/opt/conda/lib/python3.7/site-packages/libtpu/jax-libtpu.so
+
 # https://cloud.google.com/tpu/docs/pytorch-xla-ug-tpu-vm#changing_pytorch_version
 RUN pip uninstall -y torch && \
  pip install torch==${TORCH_VERSION} && \
  # The URL doesn't include patch version. i.e. must use 1.11 instead of 1.11.0
  pip install torch_xla[tpuvm] -f https://storage.googleapis.com/tpu-pytorch/wheels/tpuvm/torch_xla-${TORCH_VERSION%.*}-cp37-cp37m-linux_x86_64.whl && \
+ cp $DEFAULT_LIBTPU $PYTORCH_LIBTPU && \
  /tmp/clean-layer.sh
 
 # https://cloud.google.com/tpu/docs/jax-quickstart-tpu-vm#install_jax_on_your_cloud_tpu_vm
 RUN pip install "jax[tpu]>=0.2.16" -f https://storage.googleapis.com/jax-releases/libtpu_releases.html && \
+ cp $DEFAULT_LIBTPU $JAX_LIBTPU && \
  /tmp/clean-layer.sh
+
+# Monkey-patch JAX & PYTORCH to load the correct libtpu.so when they are imported:
+RUN sed -i "s|^\(\(.*\)libtpu.configure_library_path.*\)|\1\n\2os.environ['TPU_LIBRARY_PATH'] = '${PYTORCH_LIBTPU}'|" /opt/conda/lib/python3.7/site-packages/torch_xla/__init__.py && \
+ sed -i "s|^\(\(.*\)libtpu.configure_library_path.*\)|\1\n\2os.environ['TPU_LIBRARY_PATH'] = '${JAX_LIBTPU}'|" /opt/conda/lib/python3.7/site-packages/jax/_src/cloud_tpu_init.py

tpu/config.txt

@@ -1,5 +1,4 @@
 # TODO(b/213335159): Use ci-pretest for BASE_IMAGE_TAG once stable.
-BASE_IMAGE_TAG=v108
-LIBTPU_IMAGE_TAG=libtpu_1.1.0_RC00
+BASE_IMAGE_TAG=v115
 TENSORFLOW_VERSION=2.8.0
 TORCH_VERSION=1.11.0