Marzieh BerenjkoubRCCL 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
cd tools/topo_expl
make
Usage
./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 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 to show the topology information and print out the constructed rings/trees. However, for the convenience of just printing the algo/proto table, we use version NCCL_DEBUG=version in this example to avoid printing topo details.
# 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 a multi-node MI350 configuration with 2 nodes
NCCL_DEBUG=version ./topo_expl -m 59 -n 2
# 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
# cmd used
NCCL_DEBUG=version ./topo_expl -m 55 -n 8
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 |
...