Use mxnet==1.5.0 for CPU Dockerfile until issues with 1.6.0 and 1.7.0…

… are resolved (#2426)

Signed-off-by: Travis Addair <tgaddair@gmail.com>

Dockerfile.cpu

@@ -3,7 +3,7 @@ FROM ubuntu:18.04
 ENV TENSORFLOW_VERSION=2.3.0
 ENV PYTORCH_VERSION=1.6.0
 ENV TORCHVISION_VERSION=0.7.0
-ENV MXNET_VERSION=1.6.0
+ENV MXNET_VERSION=1.5.0
 
 # Python 3.7 is supported by Ubuntu Bionic out of the box
 ARG python=3.7
@@ -57,7 +57,7 @@ RUN mkdir /tmp/openmpi && \
     rm -rf /tmp/openmpi
 
 # Install Horovod
-RUN HOROVOD_WITH_TENSORFLOW=1 HOROVOD_WITH_PYTORCH=1 HOROVOD_WITH_MXNET=1 \
+RUN MAKEFLAGS="-j1" HOROVOD_WITH_TENSORFLOW=1 HOROVOD_WITH_PYTORCH=1 HOROVOD_WITH_MXNET=1 \
     pip install --no-cache-dir horovod
 
 # Install OpenSSH for MPI to communicate between containers

build-docker-images.sh

@@ -19,7 +19,7 @@ function build_one()
     fi
 
     tag=horovod-build-py${py}-${device}:$(date +%Y%m%d-%H%M%S)
-    docker build -f Dockerfile.${device} -t ${tag} --build-arg python=${py} --no-cache .
+    docker build -f Dockerfile.${device} -t ${tag} --build-arg python=${py} .
     horovod_version=$(docker run --rm ${tag} pip show horovod | grep Version | awk '{print $2}')
     tensorflow_version=$(docker run --rm ${tag} pip show ${tensorflow_pkg} | grep Version | awk '{print $2}')
     pytorch_version=$(docker run --rm ${tag} pip show torch | grep Version | sed 's/+/ /g' | awk '{print $2}')
@@ -30,12 +30,12 @@ function build_one()
 }
 
 # clear upstream images, ok to fail if images do not exist
-docker rmi $(cat Dockerfile.cpu | grep FROM | awk '{print $2}') || true
-docker rmi $(cat Dockerfile.gpu | grep FROM | awk '{print $2}') || true
+# docker rmi $(cat Dockerfile.cpu | grep FROM | awk '{print $2}') || true
+# docker rmi $(cat Dockerfile.gpu | grep FROM | awk '{print $2}') || true
 
 # build for cpu and gpu
 build_one 3.7 cpu
-build_one 3.7 gpu
+# build_one 3.7 gpu
 
 # print recent images
 docker images horovod/horovod