Annex Change-Log .1 summarizes changes from the previous version of the MPI standard to the version presented by this document. Only significant changes (i.e., clarifications and new features) that might either require implementation effort in the MPI libraries or change the understanding of MPI from a user's perspective are presented. Editorial modifications, formatting, typo corrections and minor clarifications are not shown. If not otherwise noted, the section and page references refer to the locations of the change or new functionality in this version of the standard. Changes in Annexes Change-Log .2--Changes from Version 2.0 to Version 2.1 were already introduced in the corresponding sections in previous versions of this standard.