3.4.85 –reduction

Recognize reduction operations in loops.

Analyze loops for reduction operations during automatic parallelization. There is potential for roundoff error with the reduction.

A reduction operation accumulates the elements of an array into a single scalar value. For example, summing the elements of a vector is a typical reduction operation. Although these operations violate the criteria for parallelizability, the compiler can recognize them and parallelize them as special cases when -reduction is specified. See the Fortran Programming Guide chapter “Parallelization” for information on reduction operations recognized by the compilers.

This option is usable only with the automatic parallelization option —autopar. It is ignored otherwise. Explicitly parallelized loops are not analyzed for reduction operations.