Purpose
The omp critical directive identifies a section of code that must be executed by a single thread at a time.
Syntax
.-,------. V | >>-#--pragma--omp critical----(name)-+-------------------------><
where name can optionally be used to identify the critical region. Identifiers naming a critical region have external linkage and occupy a namespace distinct from that used by ordinary identifiers.
Usage
A thread waits at the start of a critical region identified by a given name until no other thread in the program is executing a critical region with that same name. Critical sections not specifically named by omp critical directive invocation are mapped to the same unspecified name.