Reduction.h

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#ifndef HALIDE_REDUCTION_H
#define HALIDE_REDUCTION_H
 
/** \file
 * Defines internal classes related to Reduction Domains
 */
 
#include "Expr.h"
 
namespace Halide {
namespace Internal {
 
class IRMutator;
 
/** A single named dimension of a reduction domain */
struct ReductionVariable {
    /**
     * A variable name for the reduction variable. This name must be a
     * valid Var name, i.e. it must not contain a <tt>.</tt> character.
     */
    std::string var;
 
    Expr min, extent;
 
    /** This lets you use a ReductionVariable as a key in a map of the form
     * map<ReductionVariable, Foo, ReductionVariable::Compare> */
    struct Compare {
        bool operator()(const ReductionVariable &a, const ReductionVariable &b) const {
            return a.var < b.var;
        }
    };
};
 
struct ReductionDomainContents;
 
/** A reference-counted handle on a reduction domain, which is just a
 * vector of ReductionVariable. */
class ReductionDomain {
    IntrusivePtr<ReductionDomainContents> contents;
 
public:
    /** This lets you use a ReductionDomain as a key in a map of the form
     * map<ReductionDomain, Foo, ReductionDomain::Compare> */
    struct Compare {
        bool operator()(const ReductionDomain &a, const ReductionDomain &b) const {
            internal_assert(a.contents.defined() && b.contents.defined());
            return a.contents < b.contents;
        }
    };
 
    /** Construct a new nullptr reduction domain */
    ReductionDomain()
        : contents(nullptr) {
    }
 
    /** Construct a reduction domain that spans the outer product of
     * all values of the given ReductionVariable in scanline order,
     * with the start of the vector being innermost, and the end of
     * the vector being outermost. */
    ReductionDomain(const std::vector<ReductionVariable> &domain);
 
    /** Construct a reduction domain from deserialization */
    ReductionDomain(const std::vector<ReductionVariable> &domain, const Expr &predicate, bool frozen);
 
    /** Return a deep copy of this ReductionDomain. */
    ReductionDomain deep_copy() const;
 
    /** Is this handle non-nullptr */
    bool defined() const {
        return contents.defined();
    }
 
    /** Tests for equality of reference. Only one reduction domain is
     * allowed per reduction function, and this is used to verify
     * that */
    bool same_as(const ReductionDomain &other) const {
        return contents.same_as(other.contents);
    }
 
    /** Immutable access to the reduction variables. */
    const std::vector<ReductionVariable> &domain() const;
 
    /** Add predicate to the reduction domain. See \ref RDom::where
     * for more details. */
    void where(Expr predicate);
 
    /** Return the predicate defined on this reduction domain. */
    Expr predicate() const;
 
    /** Set the predicate, replacing any previously set predicate. */
    void set_predicate(const Expr &);
 
    /** Split predicate into vector of ANDs. If there is no predicate (i.e. all
     * iteration domain in this reduction domain is valid), this returns an
     * empty vector. */
    std::vector<Expr> split_predicate() const;
 
    /** Mark RDom as frozen, which means it cannot accept new predicates. An
     * RDom is frozen once it is used in a Func's update definition. */
    void freeze();
 
    /** Check if a RDom has been frozen. If so, it is an error to add new
     * predicates. */
    bool frozen() const;
 
    /** Pass an IRVisitor through to all Exprs referenced in the
     * ReductionDomain. */
    void accept(IRVisitor *) const;
 
    /** Pass an IRMutator through to all Exprs referenced in the
     * ReductionDomain. */
    void mutate(IRMutator *);
};
 
void split_predicate_test();
 
}  // namespace Internal
}  // namespace Halide
 
#endif