Chapter 7  Engines and Threads

Starting with release 7.0, ECLⁱPS^e supports multiple engines and multi-threaded execution.

An engine is an entity with its own data areas and potentially independent control flow. This implies:

• engines can execute queries independently of each other
• each engine has its own search tree, backtracking in one engine does not affect others
• engines can operate in a concurrent or interleaved fashion
• communication between engines is explicit
• data transferred between engines is copied, variables cannot be shared

On the other hand, engines share or can share the following:

• loaded modules and predicates
• non-logical storage such as global variables, records, stores, shelves
• global settings (set_flag/2,3)
• streams

An engine can optionally be associated with a thread, allowing it to execute concurrently with other engines.

For more details, see the Reference Manual Section on Engines.