The JVM may be able to do popcount optimization but it's categorically bad at other vectorization instructions. On Wed, Feb 24, 2016 at 18:30 Taro L. Saito <l...@xerial.org> wrote:
> Thanks for letting me know. > > If we need to embed C++ binaries (.so files) inside java, > snappy-java's approach https://github.com/xerial/snappy-java would be > useful, > which bundles .so files built for several OS/CPU architectures, and loads > one of them at run-time. > > Btw, JVM is smart enough to replace Long.bitCount(long) (popcount) into a > corresponding CPU operation. > No JNI is necessary for this. > > > On Wed, Feb 24, 2016 at 1:11 PM, Wes McKinney <w...@cloudera.com> wrote: > > > I will soon need some SIMD-enabled algorithms for hashing and > > bitmap-related stuff like popcount in the C++ implementation; we might > > prioritize a batchy JNI interface to Arrow C++ to use for cases where > > the JNI overhead is worth paying from the Java side. > > > > On Wed, Feb 24, 2016 at 11:30 AM, Jacques Nadeau <jacq...@apache.org> > > wrote: > > > The short answer is the JVM is horrible at SIMD. It does a few > > > optimizations when working with primitive arrays but beyond that, > you're > > > basically stuck working outside the JVM. The key for Arrow is that the > > > overhead of stepping out of the JVM can be amortized across all records > > in > > > a batch. I hope to contribute some examples of this cross use with > > > benchmarks shortly but would love it if others also did some work here. > > > > > > On Wed, Feb 24, 2016 at 2:22 AM, Taro L. Saito <l...@xerial.org> wrote: > > > > > >> Hi, > > >> > > >> I have just started looking at the java code of Arrow. So far what I > can > > >> found is: > > >> - Code template is used to generate efficient codes for > reading/writing > > >> fixed bit-length value vectors > > >> - Unsafe class will be used to accelerate raw memory access within > > >> ByteBuffer > > >> - ValueHolder class is used to avoid object construction costs > > >> > > >> msgpack-java (https://github.com/msgpack/msgpack-java) is also using > > >> similar techniques, so these optimizations are totally make sense. > > >> > > >> But I still cannot find where SIMD operations will work effectively. > > >> Using JNI to invoke SIMD ops will have non-negligible overhead. So my > > guess > > >> is Arrow will rely on some JVM optimization. > > >> > > >> Could you tell me how SIMD operations will be used in Arrow java? > > >> Thanks in advance, > > >> -- > > >> Taro L. Saito > > >> http://xerial.org/leo > > >> > > > > > > -- > Taro L. Saito > http://xerial.org/leo > -- -- Cheers, Leif
