= Surface Distance Cache Tests =

== Overview and Benchmark Procedure ==

I have externalized the caching functionality in our various fault surface classes. There are a couple different implementation of the new SurfaceDistanceCache interface:

* Traditional, single location cache: org.opensha.sha.faultSurface.cache.SingleLocDistanceCache
* Google guava loading cache with variable size: org.opensha.sha.faultSurface.cache.MultiDistanceCache
* Hybrid of both caches: org.opensha.sha.faultSurface.cache.HybridDistanceCache

Caching style/parameters are configurable via the org.opensha.sha.faultSurface.cache.SurfaceCachingPolicy class, which can be configured via java properties. It defaults to using some form of multiple/hybrid cache for all surfaces except for Compound Surfaces, which default to the single cache.

I then ran lots of tests at HPCC with many variations on these caching schemes. All tests were run on nodes with the exact same configuration:

2 quad core 2.5 GHz processors, 12 GB RAM.

I ran the following benchmarks for a UCERF3 ERF with the branch average solution:

Distance test: how long does it take to calculate each distance metric from 80 sites to every rupture in the ERF?
Hazard test: how long does it take to calculate a hazard curve at 80 sites?

Sites are randomly distributed (tightly) around 35, -118. Tests were run with 1, 2, 4, and 8 threads (multiple runs of each configuration and times averaged).

=== Plot Legend ===

Each plot has a number of lines. Solid lines (force=false) mean that the surfaces used the given cache for all rupture surfaces except for CompoundSurfaces, which used the single location cache. Dashed lines (force=true) use the given cache for compound surfaces as well. If size == 1 and force=false, the single location cache is used for all surfaces (this is the previous surface caching behavior).

The color is related to the cache size:
* black = 1 (the solid black line represents the previous caching behavior, and is the line to beat)
* blue = 2
* green = 4
* orange = 8
* magenta = 12

== First Results and Sensitivity to Java Version ==

These are the initial results comparing the multi cache with the given size and a 1 hour access expiration with the single cache.

||= '''Distance Test''' =||= '''Hazard Test''' =||
||[[Image(direct_1_results.png)]]||[[Image(hazard_1_results.png)]]||
||distance test, Java 6, multi cache with expiration||hazard test, Java 6, multi cache with expiration||