ai.01 · Scenario S1

Large-Scale Distributed Training

Synchronization-induced performance collapse in hyperscale distributed training fabrics operating in post-linear scaling regimes.

Scenario Definition

System Class

Hyperscale distributed training fabric with synchronous collective operations

Scale

Post-linear scaling regime with thousands of accelerators

Operational Mode

Synchronous data-parallel training with model sharding

Runtime Profile

Long-running jobs with periodic checkpointing

Recognition Pattern

Scaling works, but not like it used to. Re-runs increase, runtime variance grows, energy consumption outpaces output growth.

Structural Observations

Performance collapse emerges from correct components operating in structural coupling, not from component failure.

  • Synchronization barriers transform local jitter into global stalls that compound across training iterations
  • Thermal drift and load variations create time-varying coupling patterns invisible to static topology analysis
  • Checkpoint-restart cycles amplify rather than reset instability accumulation
  • Critical paths shift dynamically based on coupling state, not static topology

Stability Projection

Baseline

Marginal
Reserve: Depleted

With Structural Control

Stable
Reserve: Adequate

Transition type: Regime shift via projection-informed synchronization policy

Aggregated Metrics

Normalized ratios without absolute units. Baseline values crossed out, comparison values highlighted.

Effective Throughput Ratio
0.67 0.89
Energy per Useful Step
1.48 1.08
Runtime Variance Index
0.34 0.11
Sync Delay Amplification
2.8 1.2
Replay Probability
0.18 0.04
Straggler Cascade Rate
0.23 0.06

Decision Implication

Primary insight: If distributed training shows increasing re-runs and declining cost-per-performance despite healthy hardware metrics, this indicates a structural coupling problem, not an infrastructure problem.

Monitoring limitation: Standard network metrics show nominal behavior while economic instability accumulates. The problem exists between correctly functioning components.

Scaling consideration: Adding capacity increases coupling surface area and may accelerate instability rather than resolve it.

Evidence & Artefacts

Pre-computed analysis outputs for this scenario.

Such structural findings are typically contextualized through a scoped architecture risk assessment.