ENH: update docker README.md

tools/docker/README.md

@@ -74,7 +74,8 @@ docker build --network='host' -t otbtf:oldstable-gpu --build-arg BASE_IMG=nvidia
 
 ### Build for another machine and save TF compiled files 
 ```bash
-# Use same ubuntu and CUDA version than your target machine, beware of CC optimization and CPU compatibilty (avoid "-march=native")
+# Use same ubuntu and CUDA version than your target machine, beware of CC optimization and CPU compatibilty
+# (set env variable CC_OPT_FLAGS and avoid "-march=native" if your Docker's CPU is optimized with AVX2/AVX512 but your target CPU isn't)
 docker build --network='host' -t otbtf:custom --build-arg BASE_IMG=nvidia/cuda:11.2.2-cudnn8-devel-ubuntu20.04 \
     --build-arg TF=v2.5.0 --build-arg ZIP_TF_BIN=true .
 # Retrieve zip file
@@ -86,14 +87,14 @@ unzip tf-v2.5.0.zip
 sudo mkdir -p /opt/tensorflow/lib
 sudo mv tf-v2.5.0/libtensorflow_cc* /opt/tensorflow/lib
 # You may need to create a virtualenv, here TF and dependencies are installed next to user's pip packages
-pip3 install --no-cache-dir -U pip wheel mock six future deprecated "numpy==1.19.*"
-pip3 install --no-cache-dir --no-deps keras_applications keras_preprocessing
+pip3 install -U pip wheel mock six future deprecated "numpy==1.19.*"
+pip3 install --no-deps keras_applications keras_preprocessing
 pip3 install tf-v2.5.0/tensorflow-2.5.0-cp38-cp38-linux_x86_64.whl
 
 TF_WHEEL_DIR="$HOME/.local/lib/python3.8/site-packages/tensorflow"
 # If you installed the wheel as regular user, with root pip it should be in /usr/local/lib/python3.*, or in your virtualenv lib/ directory
 mv tf-v2.5.0/tag_constants.h $TF_WHEEL_DIR/include/tensorflow/cc/saved_model/
-# Then recompile OTB with OTBTF using libraries in /opt/tensorflow/lib and instructions in [HOWTOBUILD.md](../../doc/HOWTOBUILD.md).
+# Then recompile OTB with OTBTF using libraries in /opt/tensorflow/lib and instructions in HOWTOBUILD.md.
 cmake $OTB_GIT \
     -DOTB_USE_TENSORFLOW=ON -DModule_OTBTensorflow=ON \
     -DTENSORFLOW_CC_LIB=/opt/tensorflow/lib/libtensorflow_cc.so.2 \