# High Performance Computing — HPC
```{objectives}
- Let's recap and go a little further into the UPPMAX hardware!
```
## HPC, HTC and MTC
- The Buzz word is **HPC or High Performance Computing**, but this is rather narrow focusing on fast calculation, i.e. processors and parallelism
- Many of your projects are more focusing on high throughput, large memory demands and many tasks.
- Here is a list of the three most common **Computing paradigms**:
- **HPC**: High Performance Computing — Focus on floating point operations per second (**FLOPS**, flops or flop/s)
- characterized as needing large amounts of computing power for short periods of time
- **HTC**: High-Throughput Computing —
- operations or **jobs per month or per year**.
- more interested in how many jobs can be completed over a long period of time instead of how fast.
- independent, sequential jobs that can be individually scheduled o
- **MTC**: Many-task Computing — emphasis of using many computing resources over short periods of time to accomplish many computational tasks
- bridge the gap between HTC and HPC.
- reminiscent of HTC, but including both dependent and independent tasks), where the primary metrics are measured in seconds (e.g. **FLOPS**, tasks/s, **MB/s** **I/O rates**), as opposed to operations (e.g. jobs) per month.
- high-performance computations comprising multiple distinct activities, coupled via file system operations.
## What is a cluster?
- A network of computers, each computer working as a node.
- From small scale RaspberryPi cluster...
- To supercomputers like Rackham.
- Each node contains several processor cores and RAM and a local disk called scratch.
- The user logs in to login nodes via Internet through ssh or Thinlinc.
- Here the file management and lighter data analysis can be performed.
- The calculation nodes has to be used for intense computing.
- "Normal" softwares use one core.
- Parallelized software can utilize several cores or even several nodes. Keywords signalizing this are e.g.:
- "multi-threaded", "MPI", "distributed memory", "openMP", "shared memory".
- To let your software run on the calculation nodes
- start an "interactive session" or
- "submit a batch job".
- More about this in today's introduction to jobs.
## Storage basics
- All nodes can access:
- Your home directory on Domus or Castor
- Your project directories on Crex or Castor
- Its own local scratch disk (2-3 TB)
- If you’re reading/writing a file once, use a directory on Crex or Castor
- If you’re reading/writing a file many times...
- Copy the file to ”scratch”, the node local disk:
```
cp myFile $SNIC_TMP
```
## The UPPMAX hardware
### Clusters
- We have a number of compute clusters:
- [Rackham](https://www.uppmax.uu.se/resources/systems/the-rackham-cluster/)
, reserved for SNIC projects
- [Snowy](https://www.uppmax.uu.se/resources/systems/the-snowy-cluster/), GPU, long jobs reserved for UPPMAX projects and Education
- [Bianca](https://www.uppmax.uu.se/resources/systems/the-bianca-cluster/)
, a part of SNIC-SENS
- [Miarka](https://www.uppmax.uu.se/resources/systems/miarka-cluster/), reserved for Scilifelab production
- [UPPMAX cloud](https://www.uppmax.uu.se/resources/systems/the-uppmax-cloud/), a part of SNIC Science Cloud
- [User guides](https://www.uppmax.uu.se/support/user-guides/)
- The storage systems we have provide a total volume of about 25 PB, the equivalent of 50,000 years of 128-bit encoded music. Read more on the [storage systems page](https://www.uppmax.uu.se/resources/systems/storage-systems/).
### UPPMAX storage system names (projects & home directories)
- Rackham storage: Crex & Domus
- Bianca storage: Castor & Cygnus
- NGI production system (Miarka): Vulpes
- NGI delivery server: Grus
- Off-load storage: Lutra
### System usage
[System usage](https://www.uppmax.uu.se/resources/system-usage/)
- More about the systems can be found at the [System resources page](https://www.uppmax.uu.se/resources/systems/)
### A little bit more about Snowy
- [User guide](https://www.uppmax.uu.se/support/user-guides/snowy-user-guide/).
- There is a [local compute round](https://supr.snic.se/round/uppmaxcompute2021/) for UU users applying for Snowy in SUPR.
- GU (courses) applications (including GU GPU usage) are not done in SUPR, but are supposed to be routed through the service desk.
- The details can be found at the [Getting started page](https://www.uppmax.uu.se/support/getting-started/course-projects/).
### About Bianca?
- Wait for it!
## Summary about the three "common" UPPMAX clusters
| |Rackham|Snowy|Bianca|
|-------|-----|------|---|
|**Purpose**|General-purpose|General-purpose|Sensitive|
|**# Nodes (Intel)**|486+144|228+
50 Nvidia T4 GPUs|288 +
10 nodes á 2
NVIDIA A100 GPUs|
|**Cores per node**|20/16|16|16/64|
|**Memory per node**|128 GB|128 GB|128 GB
|**Fat nodes**|256 GB & 1 TB| 256, 512 GB & 4 TB| 256 & 512 GB|
|**Local disk (scratch)**|2/3 TB| 4 TB| 4 TB |
|**Login nodes**|Yes| No (reached from Rackham)|Yes (2 cores and 15 GB)|
|**"Home" storage**|Domus|Domus|Castor|
|**"Project" Storage**|Crex, Lutra|Crex, Lutra|Castor|
## Overview of the UPPMAX systems
```{mermaid}
graph TB
Node1 -- interactive --> SubGraph2Flow
Node1 -- sbatch --> SubGraph2Flow
subgraph "Snowy"
SubGraph2Flow(calculation nodes)
end
thinlinc -- usr-sensXXX + 2FA----> SubGraph1Flow
Node1 -- usr-sensXXX + 2FA----> SubGraph1Flow
subgraph "Bianca"
SubGraph1Flow(Bianca login) -- usr+passwd --> private(private cluster)
private -- interactive --> calcB(calculation nodes)
private -- sbatch --> calcB
end
subgraph "Rackham"
Node1[Login] -- interactive --> Node2[calculation nodes]
Node1 -- sbatch --> Node2
end
```
```{keypoints}
- UPPMAX has several clusters
- each having its focus and limitation or possibilites
- access is determined by type of project
```