The -par-report (Linux* and Mac OS* X) or /Qpar-report (Windows*) option controls the diagnostic levels 0, 1, 2, or 3 of the auto-parallelizer. Specify a value of 3 to generate the maximum diagnostic details.
Run the diagnostics report by entering commands similar to the following:
Operating System |
Commands |
|---|---|
Linux and Mac OS X |
ifort -c -parallel -par-report 3 sample.f90 |
Windows |
ifort /c /Qparallel /Qpar-report:3 sample.f90 |
where -c (Linux and Mac OS X) or /c (Windows) instructs the compiler to compile the example without generating an executable.
Note
Linux and Mac OS X: The space between the option and the phase is optional.
Windows: The colon between the option and phase is optional.
For example, assume you want a full diagnostic report on the following example code:
Example |
|---|
|
subroutine no_par(a, MAX) integer :: i, a(MAX) do i = 1, MAX a(i) = mod((i * 2), i) * 1 + sqrt(3.0) a(i) = a(i-1) + i end do end subroutine no_par |
The following example output illustrates the diagnostic report generated by the compiler for the example code shown above. In most cases, the comment listed next to the line is self-explanatory.
Example Report Output |
|---|
|
procedure: NO_PAR sample.f90(7):(4) remark #15049: loop was not parallelized: loop is not a parallelization candidate sample.f90(7):(4) remark #15050: loop was not parallelized: existence of parallel dependence sample.f90(13):(6) remark #15051: parallel dependence: proven FLOW dependence between A line 13, and A line 13 |
Responding to the results
The -par-threshold{n) (Linux* and Mac OS* X) or /Qpar-threshold[:n] (Windows*) option sets a threshold for auto-parallelization of loops based on the probability of profitable execution of the loop in parallel. The value of n can be from 0 to 100. You can use -par-threshold0 (Linux and Mac OS X) or /Qpar-threshold:0 (Windows) to auto-parallelize loops regardless of computational work.
Use -ipo[value] (Linux and Mac OS X) or /Qipo (Windows) to eliminate assumed side-effects done to function calls.
Use the !DEC$ PARALLEL directive to eliminate assumed data dependency.