ADIOS2 query API

The query API in ADIOS2 allows a client to pass a query in XML or json format, and get back a list of blocks or sub-blocks that contains hits. Both BP4 and BP5 engines are supported.

The interface

User is expected to pass a query file (configFile), and init a read engine (engine) to construct a query and evaluate using the engine. (note that the engine and query should be using the same ADIOS IO)

class QueryWorker
{
public:
    // configFile has query, can be either xml or json
    QueryWorker(const std::string &configFile, adios2::Engine &engine);

         // touched_blocks is a list of regions specified by (start, count),
         // that contains data that satisfies the query file
    void GetResultCoverage(std::vector<adios2::Box<adios2::Dims>> &touched_blocks);
...
}

A Sample Compound Query

This query targets a 1D variable “doubleV”, data of interest is (x > 6.6) or (x < -0.17) or (2.8 < x < 2.9) In addition, this query also specied an output region [start=5,count=80].

<adios-query>
  <io name="query">
  <var name="doubleV">
    <boundingbox  start="5" count="80"/>
    <op value="OR">
      <range  compare="GT" value="6.6"/>
      <range  compare="LT" value="-0.17"/>
      <op value="AND">
         <range  compare="LT" value="2.9"/>
         <range  compare="GT" value="2.8"/>
      </op>
    </op>
  </var>
  </io>
</adios-query>

Code EXAMPLES:

C++:

while (reader.BeginStep() == adios2::StepStatus::OK)
{
    adios2::QueryWorker w = adios2::QueryWorker(queryFile, reader);
    w.GetResultCoverage(touched_blocks);

    std::cout << " ... now can read out touched blocks ... size=" << touched_blocks.size()
              << std::endl;
}

The Full C++ example is here:

https://github.com/ornladios/ADIOS2/blob/master/examples/query/test.cpp

Python:

while (reader.BeginStep() == adios2.StepStatus.OK):
# say only rank 0 wants to process result
var = [queryIO.InquireVariable("T")]

if (rank == 0):
    touched_blocks = w.GetResult()
    doAnalysis(reader, touched_blocks, var)

Full python example is here:

https://github.com/ornladios/ADIOS2/blob/master/testing/adios2/bindings/python/TestQuery.py

This example generates data, the query file (in xml) and runs the query, all in python.