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Effects based parallel IO for OCaml.
Eio provides support for concurrency (juggling many tasks) and parallelism (using multiple CPU cores for performance).
It provides facilities for creating and coordinating fibers (light-weight threads) and domains (for parallel processing), as well as interfaces for interacting with resources provided by the operating system.
These features must be used within an event loop, provided by an Eio backend. Applications can use Eio_main.run to run a suitable loop.
val traceln :
?__POS__:(string * int * int * int)->('a, Stdlib.Format.formatter, unit, unit)Stdlib.format4->'a
traceln fmt outputs a debug message (typically to stderr).
Trace messages are printed by default and do not require logging to be configured first. The message is printed with a newline, and is flushed automatically. traceln is intended for quick debugging rather than for production code.
Unlike most Eio operations, traceln will never switch to another fiber; if the OS is not ready to accept the message then the whole domain waits.
It is safe to call traceln from multiple domains at the same time. Each line will be written atomically.
Examples:
traceln "x = %d" x;
traceln "x = %d" x ~__POS__; (* With location information *)
parameter__POS__
Display __POS__ as the location of the traceln call.
The general pattern here is that each type of resource has a set of functions for using it, plus a provider (Pi) module to allow defining your own implementations.
The system resources are available from the environment argument provided by your event loop (e.g. Eio_main.run).