Optuna NAS: 40 Trials to Match Hand-Tuned Architecture

The Manual Tuning Trap

Spent three weeks manually tweaking layer counts and dropout rates on a ResNet variant. 47 experiments. Meticulous spreadsheet tracking. Final accuracy: 91.2% on CIFAR-10.

Then I ran Optuna for 40 trials overnight. 91.4%.

That stung. But it also freed me from architecture obsession. Here's what I learned about making Optuna's architecture search actually work — because the default settings will waste your GPU hours.

Photo by Markus Winkler on Pexels

Why Most NAS Tutorials Mislead You

Most Optuna tutorials show you the happy path: define an objective, call study.optimize(), get magic results. What they skip is the part where your first 10 runs OOM, your trials take 3 hours each because you forgot pruning, and your final "optimal" architecture is actually just the first thing that didn't crash.

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