As long as I can remember, I have been interested in rocks, I have hundreds of them in storage. Rocks are interesting because they hold little clues about processes nobody has ever seen happen. For instance, one of the first rocks I ever took an interest in was a smooth granite pebble, which I collected […]
Category archives: Benchmarking
Floating Point: Manual Unrolling or Autovectorisation?
Java is very strict about floating point arithmetic. There’s even a keyword, strictfp, which allows you to make it stricter, ensuring you’ll get a potentially less precise but identical result wherever you run your program. There’s actually a JEP to make this the only behaviour. JLS 15.18.2 states clearly that floating point addition is not […]
Iterating Over a Bitset in Java
How fast can you iterate over a bitset? Daniel Lemire published a benchmark recently in support of a strategy using the number of trailing zeroes to skip over empty bits. I have used the same technique in Java several times in my hobby project SplitMap and this is something I am keen to optimise. I […]
Faster Floating Point Reductions
At the moment, I am working on a hobby project called SplitMap, which aims to evaluate aggregations over complex boolean expressions as fast as possible using the same high level constructs of the streams API. It’s already capable of performing logic that takes vanilla parallel streams 20ms in under 300μs, but I think sub 100μs […]
Matrix Multiplication Revisited
In a recent post, I took a look at matrix multiplication in pure Java, to see if it can go faster than reported in SIMD Intrinsics on Managed Language Runtimes. I found faster implementations than the paper’s benchmarks implied was possible. Nevertheless, I found that there were some limitations in Hotspot’s autovectoriser that I didn’t […]