An extensive list of changes since the last release is available online
at http://www-unix.mcs.anl.gov/mpi/mpich/r1_2_5changes.html
(It's difficult to destill the important changes from that file, which
is why I'm not pasting the entire collection in here.)
From the packages README:
Version 1.2.5 is primarily a bug-fix release. New features include
Significantly better collective algorithms are available.
Major changes for the globus2 device and the ch_nt device.
Information on previous versions
--------------------------------
Features new or improved in Version 1.2.4 included:
SMP support has been inproved through the use of sched_yield. SMP Systems that
are not oversubscribed can consider configuring with --disable-yeild.
A number of bugs in the ch_p4, ch_p4mpd, and ch_shmem device hae been fixed.
These could cause programs to hang or generate error messages.
Features new or improved in Version 1.2.3 included:
Bug fixes and improved-portability,
particularly in the area of Linux and Mac OS X support. Other new features
include better support for Intel compilers, particularly for IA64 Linux,
better support for various Fortran compilers, and some fixes for rare race
conditions in the ch_p4 device. The documentation on the ch_p4mpd device and
the MPD system has been improved. Version 1.2.3 also includes all of the
source for both the Unix and Windows versions. Windows users should still
use the self-installing version available through the web page. The globus
device now supports version 2 of Globus.
Features new or improved in Version 1.2.2 included:
There are a number of improvements to the ch_p4 device that improve both
performance and reliability, particularly on Linux platforms.
Significant upgrades have been made to the MPD system of daemons that provide
fast startup of MPICH jobs, management of stdio, and a crude parallel debugger
based on gdb.
