# Launchers

## Types

### direct (default)

By default, jobs are launched directly by the scheduler using python scripts.

### Slurm (since 0.8.7)

The [Slurm](https://slurm.schedmd.com/documentation.html) workload manager launcher is supported.
It is possible to use different settings for different jobs by using the `config`
method of the launcher

```py3

from experimaestro.launchers.slurm import SlurmLauncher

launcher = SlurmLauncher(nodes=1)
gpulauncher = launcher.config(gpu_per_node=1)

with experiment(launcher=launcher):
    # Default
    mytask().submit()

    # If needed, options can be used
    mytask().submit(launcher=gpulauncher)
```

The Slurm launcher constructor and the `config` method can take the following parameters:

- `nodes`: Number of requested nodes
- `time`: Maximum job time (in seconds)
- `gpus`: Total number of GPUs
- `gpus_per_node`: Number of GPUs per node
- `account`: The slurm account for launching the job
- `qos`: The requested Quality of Service

To use launcher configuration files, one can use an automatic convertion tool

```sh
scontrol show nodes | experimaestro launchers slurm convert
```

## Launcher configuration file (since 0.11, alpha)

In order to automate the process of choosing the right launcher, a `launchers.yaml`
configuration file can be written.

```py
# Finds a launcher so that we get 2 CUDA GPUs with 14G of memory (at least) on each
from experimaestro.launcherfinder import cuda_gpu, find_launcher
gpulauncher = find_launcher(cuda_gpu(mem="14G") * 2)
```

Example of a configuration

```yaml
# Local launchers
local:
  - # Standard launcher for small tasks
    connector: local

    # Describes the available CPUs
    cpu: { cores: 40, memory: 1G }

  - # Intensive launcher with more memory and GPU
    connector: local

    # Use a token to avoid running too many tasks
    tokens:
      localtoken: 1

    cpu: { cores: 40, memory: 8G }

    gpus:
      - model: GTX1080
        count: 1
        memory: 8116MiB

# Slurm launchers
slurm:
  - # The way to connect to the SLURM host
    connector: slurm.gateway.com

    # Describes the GPU features and link them to the two
    # possible properties (memory and number of GPUs)
    features_regex:
      - GPU(?P<cuda_count>\d+)
      - GPUM(?P<cuda_memory>\d+G)

    partitions:
      # Partition "big GPUs"
      biggpus:
        # has two types of nodes
        nodes:
          - # Nodes yep/yop
            hosts: [yop, yep]
            # Associated features
            features: [GPU3, GPUM48G]
          - hosts: [yip, yup, yap]
            features: [GPU2, GPUM24G]

      # Partition "Small GPUs"
      smallgpus:
        nodes:
          - hosts: [alpha, beta, gamma, delta]
            features: [GPU2, GPUM24G]
```
