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# `hprof`, a real-time hierarchical profiler
[](https://travis-ci.org/cmr/hprof)
[](https://crates.io/crates/hprof)
[Documentation](https://cmr.github.io/hprof)
`hprof` is suitable only for getting rough measurements of "systems", rather
than fine-tuned profiling data. Consider using `perf`, `SystemTap`, `DTrace`,
`VTune`, etc for more detailed profiling.
# What is hierarchical profiling?
Hierarchical profiling is based on the observation that games are typically
organized into a "tree" of behavior. You have an AI system that does path
planning, making tactical decisions, etc. You have a physics system that does
collision detection, rigid body dynamics, etc. A tree might look like:
- Physics
- Collision detection
- Broad phase
- Narrow phase
- Fluid simulation
- Rigid body simulation
- Collision resolution
- Update positions
- AI
- Path planning
- Combat tactics
- Build queue maintenance
- Render
- Frustum culling
- Draw call sorting
- Draw call submission
- GPU wait
A hierarchical profiler will annotate this tree with how much time each step
took. This is an extension of timer-based profiling, where a timer is used to
measure how long a block of code takes to execute. Rather than coding up a
one-time timer, you merely call `Profiler::enter("description of thing")` and
a new entry will be made in the profile tree.
The idea came from a 2002 article in Game Programming Gems 3, "Real-Time
Hierarchical Profiling" by Greg Hjelstrom and Byon Garrabrant from Westwood
Studios. They report having thousands of profile nodes active at a time.
# License
This software is licensed under the [Boost Software
License](http://www.boost.org/users/license.html). In short, you are free to
use, modify, and redistribute in any form without attribution.
# Example Output
```
Timing information for main loop:
setup - 1133523ns (6.725068%)
physics - 2258292ns (13.3982%)
collision - 1140731ns (50.512998%)
update positions - 1108782ns (49.098257%)
render - 13446767ns (79.778204%)
cull - 1134725ns (8.438646%)
gpu submit - 2197346ns (16.341073%)
gpu wait - 10088879ns (75.028287%)
```
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