ANN: stm-chans 1.2.0

wren ng thornton wren at
Sat May 7 07:58:59 CEST 2011

-- stm-chans 1.2.0

The stm-chans package offers a collection of channel types, similar to 
Control.Concurrent.STM.TChan but with additional features.

-- Changes (since 1.0.0)

* (Version 1.1.0) Added tryWriteTBChan.

* (Version 1.1.0) Added tryWriteTBMChan.

* Some major performance improvements in TBChan and TBMChan, thanks to 
Thomas DuBuisson. In particular, these improvements reduce contention 
between readers and writers, improving throughput by up to 2--3 times 
when producers and consumers are running in separate OS threads. The 
cost for non-parallel programs is trivial (<1% worst-case running time, 
per Criterion).

* Added estimateFreeSlotsTBChan, freeSlotsTBChan, 
estimateFreeSlotsTBMChan, and freeSlotsTBMChan. These functions return 
either the exact number or a lower-bound on the number of free slots 
available before the channels will block/retry.

* Some other minor optimizations and code improvements.

-- Long description

In particular stm-chans offers these types:

* Control.Concurrent.STM.TBChan:  Bounded FIFO channels.

     When the channel is full, writers will block/retry. This ensures 
that the writers do not get too far ahead of the readers, which helps to 
make sure that memory and cpu resources are used responsibly.

* Control.Concurrent.STM.TMChan:  Closeable FIFO channels.

     This is like TChan (Maybe a) but with a monotonicity guarantee that 
once Nothing is returned all future reads will be Nothing as well.

* Control.Concurrent.STM.TBMChan: Bounded Closeable FIFO channels.

     This combines the capabilities of TBChan and TMChan.

In addition, the stm-chans package offers a (partial) compatibility 
layer for some recent API improvements to the stm package (see ticket 
#5104 [1]). These new functions include:

* tryReadTChan :: TChan a -> STM (Maybe a)

     A version of readTChan which does not retry. Instead it returns 
Nothing if no value is available.

* peekTChan :: TChan a -> STM a

     Get the next value from the TChan without removing it, retrying if 
the channel is empty.

* tryPeekTChan :: TChan a -> STM (Maybe a)

     A version of peekTChan which does not retry. Instead it returns 
Nothing if no value is available.


-- Links




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