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******************
C++ High-Level API
******************
C++11 High-Level APIs are based on a single object `adios2::fstream`
.. caution::
DO NOT place ``use namespace adios2`` in your C++ code.
Use ``adios2::fstream`` directly to prevent conflicts with ``std::fstream``.
C++11 Write example
-------------------
.. code-block:: c++
#include <adios2.h>
...
int rank, size;
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
MPI_Comm_size(MPI_COMM_WORLD, &size);
// Nx, Ny from application, std::size_t
const adios2::Dims shape{Nx, Ny * static_cast<std::size_t>(size)};
const adios2::Dims start{0, Ny * static_cast<std::size_t>(rank)};
const adios2::Dims count{Nx, Ny};
adios2::fstream oStream("cfd.bp", adios2::fstream::out, MPI_COMM_WORLD);
// NSteps from application
for (std::size_t step = 0; step < NSteps; ++step)
{
if(rank == 0 && step == 0) // global variable
{
oStream.write<int32_t>("size", size);
}
// physicalTime double, <double> is optional
oStream.write<double>( "physicalTime", physicalTime );
// T and P are std::vector<float>
oStream.write( "temperature", T.data(), shape, start, count );
// adios2::endl will advance the step after writing pressure
oStream.write( "pressure", P.data(), shape, start, count, adios2::end_step );
}
// Calling close is mandatory!
oStream.close();
C++11 Read "step-by-step" example
---------------------------------
.. code-block:: c++
#include <adios2.h>
...
int rank, size;
MPI_Comm_rank(MPI_COMM_WORLD, &rank);
MPI_Comm_size(MPI_COMM_WORLD, &size);
// Selection Window from application, std::size_t
const adios2::Dims start{0, 0};
const adios2::Dims count{SelX, SelY};
if( rank == 0)
{
// if only one rank is active use MPI_COMM_SELF
adios2::fstream iStream("cfd.bp", adios2::fstream::in, MPI_COMM_SELF);
adios2::fstep iStep;
while (adios2::getstep(iStream, iStep))
{
if( iStep.currentstep() == 0 )
{
const std::size_t sizeOriginal = iStep.read<std::size_t>("size");
}
const double physicalTime = iStream.read<double>( "physicalTime");
const std::vector<float> temperature = iStream.read<float>( "temperature", start, count );
const std::vector<float> pressure = iStream.read<float>( "pressure", start, count );
}
// Don't forget to call close!
iStream.close();
}
``adios2::fstream`` API documentation
-------------------------------------
.. doxygenclass:: adios2::fstream
:project: CXX11
:path: ../../bindings/CXX11/cxx11/fstream
:members:
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