英語翻譯
7.When a variable in use can be modified from all threads in a team,it is necessary to
ensure that only one thread at a time is writing/updating the memory location of the
considered variable,otherwise unpredictable results will occur.
8.This directive,whether explicit or implied,identifies a sequence point at which the implementation
is required to ensure that each thread in the team has a consistent view of
certain variables in memory:the same correct value has to be seen by all threads.This directive
must appear at the precise point in the code at which the data synchronization
is required.
At a first glance it seems that this directive is not necessary,since in general the
writing/updating of shared variables has been done in such a way,that only one thread
at a time is allowed to do that.But this is only true in theory,because what the OpenMPimplementation
does to simulate the ”one thread at a time” feature is not specified by
the OpenMP specification.This is not a fault,moreover it is a door left open to the
OpenMP-implementations so that they can try to optimize the resulting code.
9.In certain do-loops some of the statements executed at each iteration need to be evaluated
in the same order as if the do-loop would be executed sequentially.