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Tensor Parallelism vs Pipeline Parallelism

🌐 Extreme Concurrency & Distributed Serving25 min225 BASE XP⌨ HANDS-ON LAB

Distributing 400B+ Parameter Models Across Multiple GPUs

When a model's weights exceed the memory of a single GPU (e.g. Llama 3.1 405B requires 810 GB in FP16), the harness must partition the model across multiple accelerators.

Parallelism Strategies

StrategyPartition AxisInterconnect RequirementPrimary Bottleneck
Tensor Parallelism (TP)Splits individual weight matrices within each layerUltra-high bandwidth (NVLink / NVSwitch @ 900 GB/s)All-Reduce communication latency between tokens
Pipeline Parallelism (PP)Splits sequential layers across different nodes/GPUsStandard PCIe / InfiniBand networkPipeline bubble idle time while waiting for downstream layers
Expert Parallelism (EP)Distributes different MoE experts across different GPUsInfiniBand / RoCE cluster networkAll-to-All communication routing tokens to experts
⌨ HANDS-ON LABConfigure 8-Way Tensor Parallel NVLink Topology
⭐ +250 XP

Shard a 405B parameter model across 8 GPUs using Tensor Parallelism with NVLink All-Reduce.

1Map model layers across 8 GPUs using Tensor Parallelism.
lab-sandbox — simulated environment
INFINITY LAB SANDBOX v2.6 — simulated shell
Type the command for the current objective. Helpers: "hint", "solution", "clear".
$
OBJECTIVE 1 / 1 — type "hint" if stuck
SYNAPSE VERIFICATION
QUERY 1 // 1
Why is Tensor Parallelism strictly limited to GPUs connected via NVLink within the same node?
Because PCIe cards cannot run CUDA
Because software licenses forbid multi-node TP
Because Ethernet cables do not support floating point numbers
Because TP requires All-Reduce communication on every single attention layer, demanding multi-hundred GB/s interconnect bandwidth to avoid stalling