singularity-it4i.md

# Singularity on IT4Innovations

On clusters, we have different versions of singularity images of operating systems. Below you can see the available operating systems singularity images.

Our bootstrap for create image, wrappers, features are [here](https://code.it4i.cz/sccs/it4i-singularity).

```console
   Salomon                      Anselm
      ├── CentOS                  ├── CentOS
      │   ├── 6.9                 │   ├── 6.9
      │   ├── 6.9-MIC             │   ├── 6.9-GPU
      │   └── 7.3                 │   └── 7.3
      ├── Debian                  ├── Debian
      │   └── 8.0                 │   └── 8.0
      └── Ubuntu                  └── Ubuntu
          └── 16.04                   └── 16.04
```

For current information on available singularity images, refer to the `ml av` and see statement the `OS`

## Available Operating Systems Images

* CentOS
* Debian
* Ubuntu

!!! note
    We support graphics cards for Anselm singularity image and support Intel Xeon Phi cards on Salomon singularity image. (OS/Version[none|-GPU|-MIC])

## IT4Innovations Wrappers

To use our singularity images we prepared special wrappers:

* image-exec
* image-mpi
* image-run
* image-shell
* image-update

The latest version of the scripts is [here](https://code.it4i.cz/sccs/it4i-singularity/tree/master/bin)

**image-exec**

Open the image and run the command inside the image.

```console
$ ml CentOS/7.3
Your image of CentOS/7.3 is at location: /home/login/.singularity/images/CentOS-7.3_20180220104046.img
$ image-exec cat /etc/centos-release
CentOS Linux release 7.3.1708 (Core)
```

**image-mpi**

MPI wrapper. More in the chapter [Examples MPI](#mpi).

**image-run**

Run the subscript inside image.

**image-shell**

Start the shell inside image.

```console
$ ml CentOS/7.3
$ image-shell
Singularity: Invoking an interactive shell within container...

Singularity CentOS-7.3_20180220104046.img:~>
```

**image-update**

If a new image (version) exists, informs the user and offers an update image.

```console
$ ml CentOS/6.9
New version of CentOS image was found. (New: CentOS-6.9_20180220092823.img Old: CentOS-6.9_20170220092823.img)
For updating image use: image-update
Your image of CentOS/6.9 is at location: /home/login/.singularity/images/CentOS-6.9_20170220092823.img
$ image-update
New version of CentOS image was found. (New: CentOS-6.9_20180220092823.img Old: CentOS-6.9_20170220092823.img)
Do you want to update local copy? (WARNING all user modification will be deleted) [y/N]: y
Updating image  CentOS-6.9_20180220092823.img
       2.71G 100%  199.49MB/s    0:00:12 (xfer#1, to-check=0/1)

sent 2.71G bytes  received 31 bytes  163.98M bytes/sec
total size is 2.71G  speedup is 1.00
New version is ready. (/home/login/.singularity/images/CentOS-6.9_20180220092823.img)
```

## Examples

In next examples, we will be use Singularity images on IT4Innovations clusters.

### Load Image

```console
$ ml CentOS/6.9
Your image of CentOS/6.9 is at location: /home/login/.singularity/images/CentOS-6.9_20180220133305.img
```

!!! tip
    First usage module with singularity image, copy singularity image from /apps/all/OS/... to your /home (.singularity/images)

### Intel Xeon Phi Cards - MIC

For example submit job `qsub -A PROJECT -q qprod -l select=1:mpiprocs=24:accelerator=true -I`

!!! info
    MIC image was prepared for only Salomon cluster

**Code for testing offload**

```c
#include <stdio.h>
#include <thread>
#include <stdlib.h>
#include <unistd.h>

int main() {

  char hostname[1024];
  gethostname(hostname, 1024);

  unsigned int nthreads = std::thread::hardware_concurrency();
  printf("Hello world, #of cores: %d\n",nthreads);
  #pragma offload target(mic)
  {
    nthreads = std::thread::hardware_concurrency();
    printf("Hello world from MIC, #of cores: %d\n",nthreads);
  }
}
```

**Compile and run**

```console
[login@r38u03n975 ~]$ ml CentOS/6.9-MIC
Your image of CentOS/6.9-MIC is at location: /home/login/.singularity/images/CentOS-6.9-MIC_20180220112004.img
[login@r38u03n975 ~]$ image-shell
Singularity: Invoking an interactive shell within container...

Singularity CentOS-6.9-MIC_20180220112004.img:~> ml intel/2017b
Singularity CentOS-6.9-MIC_20180220112004.img:~> ml

Currently Loaded Modules:
  1) GCCcore/6.3.0                 3) icc/2017.1.132-GCC-6.3.0-2.27     5) iccifort/2017.1.132-GCC-6.3.0-2.27                   7) iimpi/2017a                   9) intel/2017a
  2) binutils/2.27-GCCcore-6.3.0   4) ifort/2017.1.132-GCC-6.3.0-2.27   6) impi/2017.1.132-iccifort-2017.1.132-GCC-6.3.0-2.27   8) imkl/2017.1.132-iimpi-2017a
Singularity CentOS-6.9-MIC_20180220112004.img:~> icpc -std=gnu++11 -qoffload=optional  hello.c -o hello-host
Singularity CentOS-6.9-MIC_20180220112004.img:~> ./hello-host
Hello world, #of cores: 24
Hello world from MIC, #of cores: 244
```

### GPU Image

For example submit job `qsub -A PROJECT -q qnvidia -l select=1:ncpus=16:mpiprocs=16 -l walltime=01:00:00 -I`

!!! note
    GPU image was prepared for only Anselm cluster

**Checking nvidia driver inside image**

```console
[login@cn187.anselm ~]$ ml CentOS/6.9-GPU
Your image of CentOS/6.9-GPU is at location: /home/login/.singularity/images/CentOS-6.9-GPU_20171024164243.img
[login@cn187.anselm ~]$ image-shell
Singularity: Invoking an interactive shell within container...

Singularity CentOS-6.9-GPU_20171024164243.img:~> nvidia-smi
Fri Mar  9 13:01:06 2018       
+-----------------------------------------------------------------------------+
| NVIDIA-SMI 390.30                 Driver Version: 390.30                    |
|-------------------------------+----------------------+----------------------+
| GPU  Name        Persistence-M| Bus-Id        Disp.A | Volatile Uncorr. ECC |
| Fan  Temp  Perf  Pwr:Usage/Cap|         Memory-Usage | GPU-Util  Compute M. |
|===============================+======================+======================|
|   0  Tesla K20m          Off  | 00000000:02:00.0 Off |                    0 |
| N/A   29C    P0    51W / 225W |      0MiB /  4743MiB |     94%      Default |
+-------------------------------+----------------------+----------------------+
                                                                               
+-----------------------------------------------------------------------------+
| Processes:                                                       GPU Memory |
|  GPU       PID   Type   Process name                             Usage      |
|=============================================================================|
|  No running processes found                                                 |
+-----------------------------------------------------------------------------+
```

### MPI

For example submit job `qsub -A PROJECT -q qprod -l select=2:mpiprocs=24 -l walltime=00:30:00 -I`

!!! note
    We have seen no major performance impact from running a job in a Singularity container.

With Singularity, the MPI usage model is to call ‘mpirun’ from outside the container, and reference the container from your ‘mpirun’ command. Usage would look like this:

```console
$ mpirun -np 20 singularity exec container.img /path/to/contained_mpi_prog
```

By calling `mpirun` outside the container, we solve several very complicated work-flow aspects. For example, if `mpirun` is called from within the container it must have a method for spawning processes on remote nodes. Historically ssh is used for this which means that there must be an sshd running within the container on the remote nodes, and this sshd process must not conflict with the sshd running on that host! It is also possible for the resource manager to launch the job and (in Open MPI’s case) the Orted processes on the remote system, but that then requires resource manager modification and container awareness.

In the end, we do not gain anything by calling `mpirun` from within the container except for increasing the complexity levels and possibly losing out on some added performance benefits (e.g. if a container wasn’t built with the proper OFED as the host).

#### MPI Inside Image

```console
$ ml CentOS/6.9
$ image-shell
Singularity: Invoking an interactive shell within container...

Singularity CentOS-6.9_20180220092823.img:~> mpirun hostname | wc -l
24
```

!!! warning
    You allocate two nodes, but MPI inside image use only one node.

#### MPI Outside Image

```console
$ ml CentOS/6.9
Your image of CentOS/6.9 is at location: /home/login/.singularity/images/CentOS-6.9_20180220092823.img
$ image-mpi hostname | wc -l
48
```

## How to Use Own Image on Cluster?

1. Prepare the image on your  computer
1. Transfer the images to your `/home` directory on the cluster (for example `.singularity/image`)
1. Load module Singularity (`ml Singularity`)
1. Use your image

## How to Edit IT4Innovations Image?

1. Transfer the image to your computer
1. Modify the image
1. Transfer the image from your computer to your `/home` directory on the cluster
1. Load module Singularity (`ml Singularity`)
1. Use your image