Chroma Server

• https://github.com/mastbaum/chroma-server

This package lets you run a chroma server, which performs GPU-accelerated photon propagation for clients. Clients send chroma-server a list of initial photon vertices, and it replies with the final vertices of detected photons.

The chroma-server:

• https://github.com/mastbaum/chroma-server/blob/master/chroma_server/server.py

appears to now be integrated with chroma:

• https://bitbucket.org/chroma/chroma/src/b565b38ae23a5b7522b54af51091e2f7c4267c9c/bin/chroma-server

The original not using python objects for communication however, so it might be more directly relevant for usage from inside Geant4 C++.

Transport Mechanism : Feeding the server from Geant4 C++

1. Geant4 process collects G4Track into a ChromaPhotonList TObject containing contains std::vector<float> and std::vector<int>
2. My simple class ZMQRoot, serializes the ChromaPhotonList:TObject into bytes (using ROOT TMessage) and thence into a ZMQ message thats sent over the wire to server
3. Sever deserializes back into ChromaPhotonList:TObject that then gets converted to numpy arrays which can be communicated to GPU using PyCUDA/Chroma capabilities

Alternatives to ROOT TObject Serialization ?

boost serialization

• http://www.boost.org/doc/libs/1_43_0/libs/serialization/doc/index.html

numpy from C ?

pyzmq is able to send/receive numpy arrays (using multipart ZMQ message) with the dtype riding along as a json dict.

• http://zeromq.github.io/pyzmq/serialization.html
• https://github.com/lebedov/msgpack-numpy

Create numpy arrays in C directly from std::vector<float> ? My mysql numpy did something similar from mysql query results.

• http://stackoverflow.com/questions/214549/how-to-create-a-numpy-record-array-from-c
• http://stackoverflow.com/questions/18780570/passing-a-c-stdvector-to-numpy-array-in-python
• http://blog.enthought.com/python/numpy-arrays-with-pre-allocated-memory/
• http://realgonegeek.blogspot.tw/2013/08/how-to-pass-c-array-to-python-solution.html

To do this conveniently would need to use cython

• https://gist.github.com/GaelVaroquaux/1249305