# RCCL Topology Explorer (topo_expl)

The RCCL Topology Explorer is a tool for analyzing and exploring network topologies for RCCL (ROCm Communication Collectives Library) collective operations. It simulates various hardware configurations and displays the actual algo/proto combo selections that RCCL would make.

## Building

### Prerequisites
- ROCm/HIP development environment
- RCCL source code
- hipify-perl (for source transformation)

### Build Instructions

```bash
cd tools/topo_expl
make
```

## Usage

```bash
./topo_expl -m model_id [-n numNodes=1]
```

### Parameters

- `-m model_id`: Specifies the topology model to use (required)
- `-n numNodes`: Number of nodes to simulate (default: 1)

### Available Models

Run `./topo_expl` without arguments to see the list of available models. Each model represents a different hardware configuration. [Each model file](./models) pertains to a particular GPU model and node configuration. It can be output by RCCL through setting the environment variable `NCCL_TOPO_DUMP_FILE`. Model XMLs have been generated for simplicity.

## Example Usage: Print RCCL's algorithm/protocol selections

The tool is typically run with the `NCCL_DEBUG=INFO` environment variable, but for the convenience of just printing the algo/proto table, we use version `NCCL_DEBUG=version` in this example to avoid printing topo details.

```bash
# List available models
./topo_expl

# Test MI300 configuration (model 55)
NCCL_DEBUG=version ./topo_expl -m 55

# Test a multi-node MI300 configuration with 8 nodes
NCCL_DEBUG=version ./topo_expl -m 55 -n 8

# Test MI250 configuration (model 42)
NCCL_DEBUG=version ./topo_expl -m 42

# Test a multi-node MI250 configuration with 4 nodes
NCCL_DEBUG=version ./topo_expl -m 42 -n 4
```


## Sample output

```bash
# cmd used
NCCL_DEBUG=version ./topo_expl -m 55 -n 8
```

```bash

Running fp32 production choices for algorithm/protocol/maxChannels
| Max Size(B)     | Count           | Collective      | Algorithm  | Protocol   | Max Channels |
|-----------------|-----------------|-----------------|------------|------------|--------------|
| 32              | 8               | AllReduce       | Tree       | LL         | 1            |
| 64              | 16              | AllReduce       | Tree       | LL         | 1            |
| 128             | 32              | AllReduce       | Tree       | LL         | 1            |
| 256             | 64              | AllReduce       | Tree       | LL         | 1            |
| 512             | 128             | AllReduce       | Tree       | LL         | 1            |
| 1024            | 256             | AllReduce       | Tree       | LL         | 1            |
| 2048            | 512             | AllReduce       | Tree       | LL         | 1            |
| 4096            | 1024            | AllReduce       | Tree       | LL         | 2            |
| 8192            | 2048            | AllReduce       | Tree       | LL         | 4            |
| 16384           | 4096            | AllReduce       | Tree       | LL         | 8            |
| 32768           | 8192            | AllReduce       | Tree       | LL         | 16           |
| 65536           | 16384           | AllReduce       | Tree       | LL         | 32           |
| 131072          | 32768           | AllReduce       | Tree       | LL         | 64           |
| 262144          | 65536           | AllReduce       | Tree       | LL         | 64           |
| 524288          | 131072          | AllReduce       | Tree       | LL         | 64           |
| 1048576         | 262144          | AllReduce       | Tree       | LL         | 64           |
| 2097152         | 524288          | AllReduce       | Tree       | LL128      | 64           |
| 4194304         | 1048576         | AllReduce       | Tree       | LL128      | 64           |
| 8388608         | 2097152         | AllReduce       | Tree       | LL128      | 64           |
| 16777216        | 4194304         | AllReduce       | Tree       | LL128      | 64           |
| 33554432        | 8388608         | AllReduce       | Tree       | LL128      | 64           |
| 67108864        | 16777216        | AllReduce       | Tree       | Simple     | 64           |
| 134217728       | 33554432        | AllReduce       | Tree       | Simple     | 64           |
| 268435456       | 67108864        | AllReduce       | Tree       | Simple     | 64           |
| 536870912       | 134217728       | AllReduce       | Ring       | Simple     | 64           |
| 1073741824      | 268435456       | AllReduce       | Ring       | Simple     | 64           |
| 2147483648      | 536870912       | AllReduce       | Ring       | Simple     | 64           |
| 4294967296      | 1073741824      | AllReduce       | Ring       | Simple     | 64           |
...
```

