Supported Operators

The Operator abstraction allows ADIOS2 to act upon the user application data, either from a adios2::Variable or a set of Variables in an adios2::IO object. Current supported operations are:

Data compression/decompression, lossy and lossless.

This section provides a description of the supported operators in ADIOS2 and their specific parameters to allow extra-control from the user. Parameters are passed in key-value pairs for:

Operator general supported parameters.
Operator specific supported parameters.

Parameters are passed at:

Compile time: using the second parameter of the method ADIOS2::DefineOperator
Runtime Configuration Files in the ADIOS component.

CompressorZFP

The CompressorZFP Operator is compressor that uses a lossy but optionally error-bounded compression to achieve high compression ratios.

ZFP provides compressed-array classes that support high throughput read and write random access to individual array elements. ZFP also supports serial and parallel (OpenMP and CUDA) compression of whole arrays, e.g., for applications that read and write large data sets to and from disk.

ADIOS2 provides a CompressorZFP operator that lets you compress an decompress variables. Below there is an example of how to invoke CompressorZFP operator:

adios2::IO io = adios.DeclareIO("Output");
auto ZFPOp    = adios.DefineOperator("CompressorZFP", adios2::ops::LossyZFP);

auto var_r32 = io.DefineVariable<float>("r32", shape, start, count);
var_r32.AddOperation(ZFPOp, {{adios2::ops::zfp::key::rate, rate}});

CompressorZFP Specific parameters

The CompressorZFP operator accepts the following operator specific parameters:

`CompressorZFP` available parameters
`accuracy`	Fixed absolute error tolerance
`rate`	Fixed number of bits in a compression unit
`precision`	Fixed number of uncompressed bits per value
`backend`	Backend device: `cuda` `omp` `serial`

CompressorZFP Execution Policy

CompressorZFP can run in multiple backend devices: GPUs (CUDA), OpenMP, and in the host CPU. By default CompressorZFP will choose its backend following the above order upon the availability of the device adapter.

Exceptionally, if its corresponding ADIOS2 variable contains a CUDA memory address, this is a CUDA buffer, the CUDA backend will be called if available.

In any case, the user can manually set the backend using the ZFPOperator specific parameter backend.

Plugin Operator

For details on using the Plugin Operator, see the Plugins documentation.

Encryption

The Encryption Operator uses the Plugins interface. This operator uses libsodium for encrypting and decrypting data. If ADIOS can find libsodium at configure time, this plugin will be built.

This operator will generate a secret key and encrypts the data with the key and a nonce as described in the libsodium secret key cryptography docs. The key is saved to the specified SecretKeyFile and will be used for decryption. The key should be kept confidential since it is used to both encrypt and decrypt the data.

Parameters to use with the Encryption operator:

Key	Value Format	Explanation
PluginName	string	Required. Name to refer to plugin, e.g., `MyOperator`
PluginLibrary	string	Required. Name of shared library, `EncryptionOperator`
SecretKeyFile	string	Required. Path to secret key file