Timeline

Overview

The Timeline chart draws one horizontal bar per trial spanning its start and completion time, similar to a Gantt chart. It reveals how trials were scheduled over wall-clock time — how many ran in parallel, whether workers were idle, and where slow trials created bottlenecks.

Controls

This chart has no additional controls; the X-axis unit (seconds, minutes, or hours) is chosen automatically based on the total time span of the study.

Operations

Pan, zoom, and reset follow the standard 2D chart controls.

• Hover: Hover over a bar to highlight it and see a tooltip with the trial number, state, start, end, and duration. Other bars are dimmed while one is highlighted.

How to Read

• X axis: elapsed time since the study's earliest recorded trial start (re-based to zero). The unit switches automatically — seconds for short studies, minutes beyond 10 minutes, hours beyond 2 hours.
• Y axis: trial number.
• Bar length: the trial's execution duration. Running trials (no recorded completion time yet) are drawn up to the latest known timestamp in the study.
• Color by trial state: complete, pruned, running, and failed trials are colored differently (see the legend).
• Many overlapping bars at the same time: trials ran in parallel — the number of overlapping bars at any vertical slice approximates the number of concurrent workers.
• Gaps between bars on the time axis: workers were idle, e.g. waiting for a new trial to be scheduled or for a shared resource.
• A few very long bars: some trials took much longer than others — worth checking whether those hyperparameters are inherently expensive (e.g. large models) or the trial got stuck.
• Overlapping bars: when optimization is run in parallel, multiple trials may be executing during the same time window. This view is useful for confirming that parallelization is behaving as expected.