coThreads is a concurrent programming library for OCaml. It enhances the Threads library of the standard OCaml distribution in two dimensions:

• coThreads implements the same API of the standard Threads library on different execution engines (process, netwoker(todo)), so that a single copy of source code can be compiled and deployed to different environments without modification
• coThreads is also a super set of the standard Threads library, with extra components (STM etc.), functions (spawn etc.) and features (object-level compatibility etc.)

The design of coThreads brings several advantages:

• The process engine can give you real speedup on multi-core and multi-processor machines, the networker engine (todo) will give you both speedup and scalability.
• Combining the original components from the Threads library and the newly added ones, coThreads is a full-fledged toolbox covering two main concurrent programming paradigms, namely shared-memory and message passing, with both high-level and low-level constructors.
• All constructors (e.g. thread, mutex, condition, event, channel, tvar, stm etc.) are first class values that can be communicated and shared between independent threads.

• Full compatibility with the original Threads library (systhreads and vmthreads), so that you can now deploy your legacy code to new environment for free — without modifying source code, without learning something new.
• Both source-level and object-level compatibility among different execution engines, so that you can keep a single copy of source code as well as a single copy of objects files.

• The full library is implemented in user-space, no modification to the OCaml compiler and runtime, so that you can use it as a set of plain modules.
• Switching engines is as easy as changing the include paths of compilation, and it's quite easy to automate the building process over a set of engines (e.g. with lines of pattern rules in your Makefile)