Update v2.4.md

CHANGES/v2.4.md

@@ -164,9 +164,9 @@ Changes from version 2.3 which are relevant for developers:
 ## Version 2.4.1
 
 For users:
-  - Fixed an important bug affecting RMSD calculations with compilers supporting OpenMP 4 (e.g.: intel compiler). Notice that this bug affect not only
+  - Fixed an important bug affecting RMSD calculations with compilers supporting OpenMP 4 (e.g.: intel compiler). Notice that this bug might potentially affect not only
     \ref RMSD variable, but also \ref PATHMSD variables using RMSD, \ref FIT_TO_TEMPLATE, \ref PCAVARS, and possibly other variables based on RMSD calculations and optimal alignments
-    (see \issue{343}.
+    (see \issue{343}). Results might depend on the exact architecture and on how aggressive is the compiler. The bug is a consequence of some erroneous SIMD directives introduced in 2.4.0, so it does not affect PLUMED 2.3.x. 
   - Resolved a problem with \ref CS2BACKBONE and glycine atom names.
   - Module VES: Fixed a bug with basis functions that have a constant function different from 1 (e.g. scaled version of the Legendre basis functions, \ref BF_LEGENDRE) that was causing a time-dependent shift in the bias potential.
   - Module VES: In optimizers (\ref OPT_AVERAGED_SGD and \ref OPT_DUMMY) the output of quantities related to the instantaneous gradients are now off by default as these quantities are generally not useful for normal users, their output can instead by re-enabled by using the MONITOR_INSTANTANEOUS_GRADIENT keyword. Also added an keyword MONITOR_AVERAGE_GRADIENT that allows to monitor the averged gradient and output quantities related to it.