Data Scope Attribute Clauses
“firstprivate” Clause
Purpose: The firstprivate clause combines the behavior of the private clause with automatic initialization of the variables in the list
Format: firstprivate (list)
- Special case of private clause
- Initializes each private copy with the corresponding value from the master thread prior to entry into the parallel or work-sharing construct
The “firstprivate” Clause
Example: “firstprivate” Clause
void useless() {
int tmp = 0;
#pragma omp parallel for firstprivate(tmp)
for (int j = 0; j ¡ 1000; ++j)
tmp += j;
printf(“%d”, tmp);
} |
- Each thread gets its own code with initial value 0.Is there something still wrong with the code ?
- What value of tmp it will be printed in second last line ?
- Tmp is unspecified for OpenMP 2.5 while 0 in OpenMP 3.0
“lastprivate” Clause
Purpose: The lastprivate clause combines the behavior of the private clause with a copy from the last loop iteration or section to the original variable object.
Format: lastprivate (list)
- The value copied back into the original variable object is obtained from the last (sequentially) iteration or section of the enclosing construct.
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