MPI Training

This guide walks you through using MPI for training.

The MPI Operator makes it easy to run allreduce-style distributed training on Kubernetes. Please check out this blog post for an introduction to MPI Operator and its industry adoption.

Installation

You can deploy the operator with default settings by running the following commands:

git clone https://github.com/kubeflow/mpi-operator
cd mpi-operator
kubectl create -f deploy/v1alpha2/mpi-operator.yaml

Alternatively, follow the getting started guide to deploy Kubeflow.

An alpha version of MPI support was introduced with Kubeflow 0.2.0. You must be using a version of Kubeflow newer than 0.2.0.

You can check whether the MPI Job custom resource is installed via:

kubectl get crd

The output should include mpijobs.kubeflow.org like the following:

NAME                                       AGE
...
mpijobs.kubeflow.org                       4d
...

If it is not included you can add it as follows using kustomize:

git clone https://github.com/kubeflow/mpi-operator
cd mpi-operator/manifests
kustomize build overlays/kubeflow | kubectl apply -f -

Note that since Kubernetes v1.14, kustomize became a subcommand in kubectl so you can also run the following command instead:

kubectl kustomize base | kubectl apply -f -

Creating an MPI Job

You can create an MPI job by defining an MPIJob config file. See TensorFlow benchmark example config file for launching a multi-node TensorFlow benchmark training job. You may change the config file based on your requirements.

cat examples/v1alpha2/tensorflow-benchmarks.yaml

Deploy the MPIJob resource to start training:

kubectl create -f examples/v1alpha2/tensorflow-benchmarks.yaml

Monitoring an MPI Job

Once the MPIJob resource is created, you should now be able to see the created pods matching the specified number of GPUs. You can also monitor the job status from the status section. Here is sample output when the job is successfully completed.

kubectl get -o yaml mpijobs tensorflow-benchmarks

apiVersion: kubeflow.org/v1alpha2
kind: MPIJob
metadata:
  creationTimestamp: "2019-07-09T22:15:51Z"
  generation: 1
  name: tensorflow-benchmarks
  namespace: default
  resourceVersion: "5645868"
  selfLink: /apis/kubeflow.org/v1alpha2/namespaces/default/mpijobs/tensorflow-benchmarks
  uid: 1c5b470f-a297-11e9-964d-88d7f67c6e6d
spec:
  cleanPodPolicy: Running
  mpiReplicaSpecs:
    Launcher:
      replicas: 1
      template:
        spec:
          containers:
          - command:
            - mpirun
            - --allow-run-as-root
            - -np
            - "2"
            - -bind-to
            - none
            - -map-by
            - slot
            - -x
            - NCCL_DEBUG=INFO
            - -x
            - LD_LIBRARY_PATH
            - -x
            - PATH
            - -mca
            - pml
            - ob1
            - -mca
            - btl
            - ^openib
            - python
            - scripts/tf_cnn_benchmarks/tf_cnn_benchmarks.py
            - --model=resnet101
            - --batch_size=64
            - --variable_update=horovod
            image: mpioperator/tensorflow-benchmarks:latest
            name: tensorflow-benchmarks
    Worker:
      replicas: 1
      template:
        spec:
          containers:
          - image: mpioperator/tensorflow-benchmarks:latest
            name: tensorflow-benchmarks
            resources:
              limits:
                nvidia.com/gpu: 2
  slotsPerWorker: 2
status:
  completionTime: "2019-07-09T22:17:06Z"
  conditions:
  - lastTransitionTime: "2019-07-09T22:15:51Z"
    lastUpdateTime: "2019-07-09T22:15:51Z"
    message: MPIJob default/tensorflow-benchmarks is created.
    reason: MPIJobCreated
    status: "True"
    type: Created
  - lastTransitionTime: "2019-07-09T22:15:54Z"
    lastUpdateTime: "2019-07-09T22:15:54Z"
    message: MPIJob default/tensorflow-benchmarks is running.
    reason: MPIJobRunning
    status: "False"
    type: Running
  - lastTransitionTime: "2019-07-09T22:17:06Z"
    lastUpdateTime: "2019-07-09T22:17:06Z"
    message: MPIJob default/tensorflow-benchmarks successfully completed.
    reason: MPIJobSucceeded
    status: "True"
    type: Succeeded
  replicaStatuses:
    Launcher:
      succeeded: 1
    Worker: {}
  startTime: "2019-07-09T22:15:51Z"

Training should run for 100 steps and takes a few minutes on a GPU cluster. You can inspect the logs to see the training progress. When the job starts, access the logs from the launcher pod:

PODNAME=$(kubectl get pods -l mpi_job_name=tensorflow-benchmarks,mpi_role_type=launcher -o name)
kubectl logs -f ${PODNAME}

TensorFlow:  1.14
Model:       resnet101
Dataset:     imagenet (synthetic)
Mode:        training
SingleSess:  False
Batch size:  128 global
             64 per device
Num batches: 100
Num epochs:  0.01
Devices:     ['horovod/gpu:0', 'horovod/gpu:1']
NUMA bind:   False
Data format: NCHW
Optimizer:   sgd
Variables:   horovod

...

40  images/sec: 154.4 +/- 0.7 (jitter = 4.0)  8.280
40  images/sec: 154.4 +/- 0.7 (jitter = 4.1)  8.482
50  images/sec: 154.8 +/- 0.6 (jitter = 4.0)  8.397
50  images/sec: 154.8 +/- 0.6 (jitter = 4.2)  8.450
60  images/sec: 154.5 +/- 0.5 (jitter = 4.1)  8.321
60  images/sec: 154.5 +/- 0.5 (jitter = 4.4)  8.349
70  images/sec: 154.5 +/- 0.5 (jitter = 4.0)  8.433
70  images/sec: 154.5 +/- 0.5 (jitter = 4.4)  8.430
80  images/sec: 154.8 +/- 0.4 (jitter = 3.6)  8.199
80  images/sec: 154.8 +/- 0.4 (jitter = 3.8)  8.404
90  images/sec: 154.6 +/- 0.4 (jitter = 3.7)  8.418
90  images/sec: 154.6 +/- 0.4 (jitter = 3.6)  8.459
100 images/sec: 154.2 +/- 0.4 (jitter = 4.0)  8.372
100 images/sec: 154.2 +/- 0.4 (jitter = 4.0)  8.542
----------------------------------------------------------------
total images/sec: 308.27

Docker Images

Docker images are built and pushed automatically to mpioperator on Dockerhub. You can use the following Dockerfiles to build the images yourself:

• mpi-operator
• kubectl-delivery

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