How to roughly control ADIOS2 block number and WarpX particle number

[Change72]

1. ADIOS2 block number:

I want to increase the ADIOS2 block number. I notice the field number is matched with grids number. For example, key = /data/600/fields/E/x. However, for particle blockNum, it seems a magic number: key = /data/600/particles/electrons/momentum/x. I didn't find any parameter to control it, and I guess there should be one in the openPMD layer.

| n_cell | max_grid_size | blocking_factor | grids | field blockNum | particle blockNum | smallest grid | biggest grid | |---|---|---|---|---|---|---|---| | 32x32x256 | 64 | 32 | 4 | 4 | 128| 32x32x64 | 32x32x64 | | 256x256x512 | 64 | 32 | 128 | 128 | 128 | 64x64x64 | 64x64x64 | | 64x64x256 | 64 | 32 | 4 | 4 | 4 | 64x64x64 | 64x64x64 | | 256x256x256 | 8 | 8 | 32768 | 32768 | 738| 8x8x8 | 8x8x8 |

    bpIO = adios.DeclareIO("ReadBP");
    bpIO.SetParameter("Threads", std::to_string(nThreads));
    bpReader = bpIO.Open(bpFileName, adios2::Mode::Read);

    adios2::Variable<double> x_meta_info = bpIO.InquireVariable<double>(key + "x");
    auto xBlocksInfo = bpReader.AllStepsBlocksInfo(x_meta_info);
    auto x_it = xBlocksInfo.begin();

    for (; x_it != xBlocksInfo.end(); ++x_it) {
        const auto &var_vec1 = x_it->second;
        std:cout << var_vec1.size() << std::endl;  // as ADIOS2 block number
    }

2. for the particle number in bpls, the injection style I used is electrons.injection_style = "NRandomPerCell". The first two lines satisfy the exception, but the third and fourth lines are quite weird.

| n_cell | iteration | num_particles_per_cell | num_particles_in_last_iteration | |---|---|---|---| | 32x32x256 | 500 | 1 | 116072 | | 32x32x256 | 500 | 100 | 11607258 | | 256x256x512 | 600 | 100 | 14069550 | | 64x64x256 | 600 | 10000 | 45020389 | | 256x256x256 | 600 | 1 | 64950 |

[ax3l]

@guj do you want to comment first? :)

[guj]

Sorry I missed this one.

For 1, yes, the number of ADIOS blocks for field related variables equals the number of sub grids. Looks like you know how to adjust number of sub grids via blocking factor/max_grid_size. I am aware of any way to predict number of blocks for particles. @ax3l can comment.

The keys you mentioned are names of ADIOS variables. Looks like you are using openPMD's group based outputs, so the time steps are embedded in the names. It has no relation with number of blocks.

For 2, Sorry I am not sure I understand the question. Maybe @ax3l can help.

[Change72]

@ax3l any idea? :)