Troubleshooting

Task::init() reports mismatching interfaces

Before planning, the planning pipeline is checked for consistency. Each stage type has a specific flow interface, e.g. generator-type stages write into both, their begin and end interface, propagator-type stages read from one and write to the opposite, and connector-type stages read from both sides. Obviously these interfaces need to match. If they don’t, an InitStageException is thrown. Per default, this is not very verbose, but you can use the following code snippet to get some more info:

try {
        task.plan();
} catch (const InitStageException& e) {
        std::cerr << e << std::endl;
        throw;
}

For example, the following pipeline:

• ↕ current

• ⛓ connect

• ↑ moveTo

throws the error: task pipeline: end interface (←) of 'moveto' does not match mine (→).

The validation process runs sequentially through a SerialContainer. Here, current, as a generator stage is compatible to connect, writing to the interface read by connect. moveTo as a propagator can operate, in principle, forwards and backwards. By default, the operation direction is inferred automatically. Here, as connect requires a reading end-interface, moveTo should seemingly operate backwards. However, now the whole pipeline is incompatible to the enclosing container’s interface: a task requires a generator-type interface as it generates solutions - there is no input interface to read from. Hence, the reading end interface (←) of moveto conflicts with a writing end interface of the task.

Obviously, in a ParallelContainer all (direct) children need to share a common interface.