New Reducer ValOp Interface

[rchen20]

Summary

• This PR is a refactoring:
• It does the following:
  • Refactors new reduction interface to have consistent min/max/loc operator semantics.
  • Introduces type safety to reduction operators.
  • Interface will be changed to require passing in ValOp objects, as opposed to the old interface which used raw data types. Changes will be highlighted with a comparison chart soon.
  • ValLoc now requires IndexType, and must be used within a ValOp, e.g. ValOp<ValLoc<T,IndexType>, Op>.
  • Satisfies this request Add Val class similar to ValLoc #1582.

Original interface:

int sum = 0;
int min = large_num;
RAJA::expt::ValLoc<T, RAJA::Index_type> minloc(large_num, -1);

RAJA::forall<seqpol>(host_res, range,

  RAJA::expt::Reduce<RAJA::operators::plus>(&sum),
  RAJA::expt::Reduce<RAJA::operators::minimum>(&min),
  RAJA::expt::Reduce<RAJA::operators::minimum>(&minloc),

  [=] (int i,
    int & _sum,
    int & _min,
    RAJA::expt::ValLoc<T,RAJA::Index_type> & _minloc) {

            _sum += a[i];
            _min = RAJA_MIN(a[i], _min);
            _minloc = RAJA_MIN(RAJA::expt::ValLoc<T,RAJA::Index_type>(a[i], i), _minloc);
});

Changes in this PR:

int sum(0);
int min(large_num);
RAJA::expt::ValLoc<T, RAJA::Index_type> minloc(large_num, -1);

RAJA::expt::ValLoc<T, RAJA::Index_type> temploc(large_num, -1);

int max = small_num;
RAJA::Index_type loc(-1);

RAJA::forall<seqpol>(host_res, range,

  RAJA::expt::Reduce<RAJA::operators::plus>(&sum),
  RAJA::expt::Reduce<RAJA::operators::minimum>(&min),
  RAJA::expt::Reduce<RAJA::operators::minimum>(&minloc),
  RAJA::expt::ReduceLoc<RAJA::operators::maximum>(&max, &loc),

  [=] (int i,
    RAJA::expt::ValOp<T, RAJA::operators::plus> & _sum,
    RAJA::expt::ValOp<T, RAJA::operators::minimum> & _min,
    RAJA::expt::ValOp<RAJA::expt::ValLoc<T, RAJA::Index_type>, RAJA::operators::minimum> & _minloc,
    RAJA::expt::ValOp<RAJA::expt::ValLoc<T, RAJA::Index_type>, RAJA::operators::maximum> & _maxloc) {

            _sum += a[i];
            _min.min(a[i]);
            _minloc.minloc(a[i], i);

            _minloc.min(temploc);

            _maxloc.maxloc(a[i], i);
});

minloc.set(large_num, -1);

Todo's:

• Clean up accessors to val
• Documentation
• Modify tests to use ValOp
• Launch
• SYCL
• OpenMP Target

Enhancements for later:

• Reset function. Like set(), but puts max/min and -1 for locs.
• Default init to min/max values and -1 for loc.
• Expand launch/reduce-param tests (BitOr, Max, locs).

[rchen20]

@rhornung67 I think the documentation issues have been addressed, please take another look when you can.
@MrBurmark The templating has been simplified according to your suggestions, please take another look.

[rchen20]

@MrBurmark Everything should be addressed now, please take another look.