Currently all packages of preCICE reference Data::values() to read or write data. Mapping, acceleration, communication and actions operate on the data in Data::values(). For time interpolation we recently introduced a write data buffer and a storage (#1612) in Data. In #1612 data has to be moved from the storage to Data::values() and vice-versa when mapping, acceleration, communication or actions are executed to not interfere with the currently existing implementation. In the future, we should, however avoid using Data::values() and instead use the data from the storage (see example below).

The following packages need a review:

• mapping (see Samplize mapping #1660, Refactor mapping to work on Storages, not on Data::values #1651)
• communication (see Directly perform extrapolation in time::Storage, only allow CouplingScheme to moveToNextWindow #1639)
• acceleration
• actions
• exporter / io

Note that this issue is mainly meant as an overview.

Example for mapping

Current state (#1612)

map accesses Data::values() using fromDataID and toDataID.

Proposed implementation:

 for (auto &stample : context.fromData->getStamples()) { 
   const Eigen::VectorXd fromData = stample.sample.values;
   const Eigen::VectorXd toData = context.mapping->map(fromData); 
   // Store data from mapping buffer in storage 
   context.toData->setSampleAtTime(stample.timestamp, toData);
 } 

map does not need to access Data::values(), because it would just operate on Eigen::VectorXd.

Benefits:

• No need for moving data back and forth
• Better encapsulation of packages