| /* reducer_opmul.h -*- C++ -*- |
| * |
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| * Copyright (C) 2012-2013, Intel Corporation |
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| |
| /** @file reducer_opmul.h |
| * |
| * @brief Defines classes for doing parallel multiplication reductions. |
| * |
| * @ingroup ReducersMul |
| * |
| * @see ReducersMul |
| */ |
| |
| #ifndef REDUCER_OPMUL_H_INCLUDED |
| #define REDUCER_OPMUL_H_INCLUDED |
| |
| #include <cilk/reducer.h> |
| |
| /** @defgroup ReducersMul Multiplication Reducers |
| * |
| * Multiplication reducers allow the computation of the product of a set of |
| * values in parallel. |
| * |
| * @ingroup Reducers |
| * |
| * You should be familiar with @ref pagereducers "Cilk reducers", described in |
| * file `reducers.md`, and particularly with @ref reducers_using, before trying |
| * to use the information in this file. |
| * |
| * @section redopmul_usage Usage Example |
| * |
| * cilk::reducer< cilk::op_mul<double> > r; |
| * cilk_for (int i = 0; i != N; ++i) { |
| * *r *= a[i]; |
| * } |
| * double product; |
| * r.move_out(product); |
| * |
| * @section redopmul_monoid The Monoid |
| * |
| * @subsection redopmul_monoid_values Value Set |
| * |
| * The value set of a multiplication reducer is the set of values of `Type`, |
| * which is expected to be a builtin numeric type (or something like it, such |
| * as `std::complex`). |
| * |
| * @subsection redopmul_monoid_operator Operator |
| * |
| * The operator of a multiplication reducer is the multiplication operation, |
| * defined by the “`*`” binary operator on `Type`. |
| * |
| * @subsection redopmul_monoid_identity Identity |
| * |
| * The identity value of the reducer is the numeric value “`1`”. This is |
| * expected to be the value of the expression `Type(1)`. |
| * |
| * @section redopmul_operations Operations |
| * |
| * @subsection redopmul_constructors Constructors |
| * |
| * reducer() // identity |
| * reducer(const Type& value) |
| * reducer(move_in(Type& variable)) |
| * |
| * @subsection redopmul_get_set Set and Get |
| * |
| * r.set_value(const Type& value) |
| * const Type& = r.get_value() const |
| * r.move_in(Type& variable) |
| * r.move_out(Type& variable) |
| * |
| * @subsection redopmul_initial Initial Values |
| * |
| * If a multiplication reducer is constructed without an explicit initial |
| * value, then its initial value will be its identity value, as long as `Type` |
| * satisfies the requirements of @ref redopmul_types. |
| * |
| * @subsection redopmul_view_ops View Operations |
| * |
| * *r *= a |
| * *r = *r * a |
| * *r = *r * a1 * a2 … * an |
| * |
| * @section redopmul_floating_point Issues with Floating-Point Types |
| * |
| * Because of overflow and underflow issues, floating-point multiplication is |
| * not really associative. For example, `(1e200 * 1e-200) * 1e-200 == 1e-200`, |
| * but `1e200 * (1e-200 * 1e-200 == 0. |
| * |
| * In many cases, this won’t matter, but computations which have been |
| * carefully ordered to control overflow and underflow may not deal well with |
| * being reassociated. In general, you should be sure to understand the |
| * floating-point behavior of your program before doing any transformation |
| * that will reassociate its computations. |
| * |
| * @section redopmul_types Type and Operator Requirements |
| * |
| * `Type` must be `Copy Constructible`, `Default Constructible`, and |
| * `Assignable`. |
| * |
| * The operator “`*=`” must be defined on `Type`, with `x *= a` having the same |
| * meaning as `x = x * a`. |
| * |
| * The expression `Type(1)` must be a valid expression which yields the |
| * identity value (the value of `Type` whose numeric value is `1`). |
| * |
| * @section redopmul_in_c Multiplication Reducers in C |
| * |
| * The @ref CILK_C_REDUCER_OPMUL and @ref CILK_C_REDUCER_OPMUL_TYPE macros can |
| * be used to do multiplication reductions in C. For example: |
| * |
| * CILK_C_REDUCER_OPMUL(r, double, 1); |
| * CILK_C_REGISTER_REDUCER(r); |
| * cilk_for(int i = 0; i != n; ++i) { |
| * REDUCER_VIEW(r) *= a[i]; |
| * } |
| * CILK_C_UNREGISTER_REDUCER(r); |
| * printf("The product of the elements of a is %f\n", REDUCER_VIEW(r)); |
| * |
| * See @ref reducers_c_predefined. |
| */ |
| |
| #ifdef __cplusplus |
| |
| namespace cilk { |
| |
| /** The multiplication reducer view class. |
| * |
| * This is the view class for reducers created with |
| * `cilk::reducer< cilk::op_mul<Type> >`. It holds the accumulator variable |
| * for the reduction, and allows only multiplication operations to be |
| * performed on it. |
| * |
| * @note The reducer “dereference” operation (`reducer::operator *()`) |
| * yields a reference to the view. Thus, for example, the view class’s |
| * `*=` operation would be used in an expression like `*r *= a`, where |
| * `r` is an op_mul reducer variable. |
| * |
| * @tparam Type The type of the contained accumulator variable. This will |
| * be the value type of a monoid_with_view that is |
| * instantiated with this view. |
| * |
| * @see ReducersMul |
| * @see op_mul |
| * |
| * @ingroup ReducersMul |
| */ |
| template <typename Type> |
| class op_mul_view : public scalar_view<Type> |
| { |
| typedef scalar_view<Type> base; |
| |
| public: |
| /** Class to represent the right-hand side of `*reducer = *reducer * value`. |
| * |
| * The only assignment operator for the op_mul_view class takes an |
| * rhs_proxy as its operand. This results in the syntactic restriction |
| * that the only expressions that can be assigned to an op_mul_view are |
| * ones which generate an rhs_proxy — that is, expressions of the form |
| * `op_mul_view * value ... * value`. |
| * |
| * @warning |
| * The lhs and rhs views in such an assignment must be the same; |
| * otherwise, the behavior will be undefined. (I.e., `v1 = v1 * x` is |
| * legal; `v1 = v2 * x` is illegal.) This condition will be checked with a |
| * runtime assertion when compiled in debug mode. |
| * |
| * @see op_mul_view |
| */ |
| class rhs_proxy { |
| friend class op_mul_view; |
| |
| const op_mul_view* m_view; |
| Type m_value; |
| |
| // Constructor is invoked only from op_mul_view::operator*(). |
| // |
| rhs_proxy(const op_mul_view* view, const Type& value) : m_view(view), m_value(value) {} |
| |
| rhs_proxy& operator=(const rhs_proxy&); // Disable assignment operator |
| rhs_proxy(); // Disable default constructor |
| |
| public: |
| /** Multiply by an additional rhs value. If `v` is an op_mul_view and |
| * `a1` is a value, then the expression `v * a1` invokes the view’s |
| * `operator*()` to create an rhs_proxy for `(v, a1)`; then |
| * `v * a1 * a2` invokes the rhs_proxy’s `operator*()` to create a |
| * new rhs_proxy for `(v, a1*a2)`. This allows the right-hand side of |
| * an assignment to be not just `view * value`, but |
| * `view * value * value ... * value`. The effect is that |
| * |
| * v = v * a1 * a2 ... * an; |
| * |
| * is evaluated as |
| * |
| * v = v * (a1 * a2 ... * an); |
| */ |
| rhs_proxy& operator*(const Type& x) { m_value *= x; return *this; } |
| }; |
| |
| |
| /** Default/identity constructor. This constructor initializes the |
| * contained value to `Type(1)`, which is expected to be the identity |
| * value for multiplication on `Type`. |
| */ |
| op_mul_view() : base(Type(1)) {} |
| |
| /** Construct with a specified initial value. |
| */ |
| explicit op_mul_view(const Type& v) : base(v) {} |
| |
| /** Reduction operation. |
| * |
| * This function is invoked by the @ref op_mul monoid to combine the views |
| * of two strands when the right strand merges with the left one. It |
| * multiplies the value contained in the left-strand view by the value |
| * contained in the right-strand view, and leaves the value in the |
| * right-strand view undefined. |
| * |
| * @param right A pointer to the right-strand view. (`this` points to |
| * the left-strand view.) |
| * |
| * @note Used only by the @ref op_mul monoid to implement the monoid |
| * reduce operation. |
| */ |
| void reduce(op_mul_view* right) { this->m_value *= right->m_value; } |
| |
| /** @name Accumulator variable updates. |
| * |
| * These functions support the various syntaxes for multiplying the |
| * accumulator variable contained in the view by some value. |
| */ |
| //@{ |
| |
| /** Multiply the accumulator variable by @a x. |
| */ |
| op_mul_view& operator*=(const Type& x) { this->m_value *= x; return *this; } |
| |
| /** Create an object representing `*this * x`. |
| * |
| * @see rhs_proxy |
| */ |
| rhs_proxy operator*(const Type& x) const { return rhs_proxy(this, x); } |
| |
| /** Assign the result of a `view * value` expression to the view. Note that |
| * this is the only assignment operator for this class. |
| * |
| * @see rhs_proxy |
| */ |
| op_mul_view& operator=(const rhs_proxy& rhs) { |
| __CILKRTS_ASSERT(this == rhs.m_view); |
| this->m_value *= rhs.m_value; |
| return *this; |
| } |
| |
| //@} |
| }; |
| |
| /** Monoid class for multiplication reductions. Instantiate the cilk::reducer |
| * template class with an op_mul monoid to create a multiplication reducer |
| * class. For example, to compute the product of a set of `double` values: |
| * |
| * cilk::reducer< cilk::op_mul<double> > r; |
| * |
| * @see ReducersMul |
| * @see op_mul_view |
| * |
| * @ingroup ReducersMul |
| */ |
| template <typename Type> |
| struct op_mul : public monoid_with_view< op_mul_view<Type> > {}; |
| |
| } // namespace cilk |
| |
| #endif // __cplusplus |
| |
| |
| /** @ingroup ReducersAdd |
| */ |
| //@{ |
| |
| /** @name C language reducer macros |
| * |
| * These macros are used to declare and work with numeric op_mul reducers in |
| * C code. |
| * |
| * @see @ref page_reducers_in_c |
| */ |
| //@{ |
| |
| __CILKRTS_BEGIN_EXTERN_C |
| |
| /** Opmul reducer type name. |
| * |
| * This macro expands into the identifier which is the name of the op_mul |
| * reducer type for a specified numeric type. |
| * |
| * @param tn The @ref reducers_c_type_names "numeric type name" specifying |
| * the type of the reducer. |
| * |
| * @see @ref reducers_c_predefined |
| * @see ReducersMul |
| */ |
| #define CILK_C_REDUCER_OPMUL_TYPE(tn) \ |
| __CILKRTS_MKIDENT(cilk_c_reducer_opmul_,tn) |
| |
| /** Declare an op_mul reducer object. |
| * |
| * This macro expands into a declaration of an op_mul reducer object for a |
| * specified numeric type. For example: |
| * |
| * CILK_C_REDUCER_OPMUL(my_reducer, double, 1.0); |
| * |
| * @param obj The variable name to be used for the declared reducer object. |
| * @param tn The @ref reducers_c_type_names "numeric type name" specifying |
| * the type of the reducer. |
| * @param v The initial value for the reducer. (A value which can be |
| * assigned to the numeric type represented by @a tn.) |
| * |
| * @see @ref reducers_c_predefined |
| * @see ReducersMul |
| */ |
| #define CILK_C_REDUCER_OPMUL(obj,tn,v) \ |
| CILK_C_REDUCER_OPMUL_TYPE(tn) obj = \ |
| CILK_C_INIT_REDUCER(_Typeof(obj.value), \ |
| __CILKRTS_MKIDENT(cilk_c_reducer_opmul_reduce_,tn), \ |
| __CILKRTS_MKIDENT(cilk_c_reducer_opmul_identity_,tn), \ |
| __cilkrts_hyperobject_noop_destroy, v) |
| |
| /// @cond internal |
| |
| /** Declare the op_mul reducer functions for a numeric type. |
| * |
| * This macro expands into external function declarations for functions which |
| * implement the reducer functionality for the op_mul reducer type for a |
| * specified numeric type. |
| * |
| * @param t The value type of the reducer. |
| * @param tn The value “type name” identifier, used to construct the reducer |
| * type name, function names, etc. |
| */ |
| #define CILK_C_REDUCER_OPMUL_DECLARATION(t,tn) \ |
| typedef CILK_C_DECLARE_REDUCER(t) CILK_C_REDUCER_OPMUL_TYPE(tn); \ |
| __CILKRTS_DECLARE_REDUCER_REDUCE(cilk_c_reducer_opmul,tn,l,r); \ |
| __CILKRTS_DECLARE_REDUCER_IDENTITY(cilk_c_reducer_opmul,tn); |
| |
| /** Define the op_mul reducer functions for a numeric type. |
| * |
| * This macro expands into function definitions for functions which implement |
| * the reducer functionality for the op_mul reducer type for a specified |
| * numeric type. |
| * |
| * @param t The value type of the reducer. |
| * @param tn The value “type name” identifier, used to construct the reducer |
| * type name, function names, etc. |
| */ |
| #define CILK_C_REDUCER_OPMUL_DEFINITION(t,tn) \ |
| typedef CILK_C_DECLARE_REDUCER(t) CILK_C_REDUCER_OPMUL_TYPE(tn); \ |
| __CILKRTS_DECLARE_REDUCER_REDUCE(cilk_c_reducer_opmul,tn,l,r) \ |
| { *(t*)l *= *(t*)r; } \ |
| __CILKRTS_DECLARE_REDUCER_IDENTITY(cilk_c_reducer_opmul,tn) \ |
| { *(t*)v = 1; } |
| |
| //@{ |
| /** @def CILK_C_REDUCER_OPMUL_INSTANCE |
| * @brief Declare or define implementation functions for a reducer type. |
| * |
| * In the runtime source file c_reducers.c, the macro `CILK_C_DEFINE_REDUCERS` |
| * will be defined, and this macro will generate reducer implementation |
| * functions. Everywhere else, `CILK_C_DEFINE_REDUCERS` will be undefined, and |
| * this macro will expand into external declarations for the functions. |
| */ |
| #ifdef CILK_C_DEFINE_REDUCERS |
| # define CILK_C_REDUCER_OPMUL_INSTANCE(t,tn) \ |
| CILK_C_REDUCER_OPMUL_DEFINITION(t,tn) |
| #else |
| # define CILK_C_REDUCER_OPMUL_INSTANCE(t,tn) \ |
| CILK_C_REDUCER_OPMUL_DECLARATION(t,tn) |
| #endif |
| //@} |
| |
| /* Declare or define an instance of the reducer type and its functions for each |
| * numeric type. |
| */ |
| CILK_C_REDUCER_OPMUL_INSTANCE(char, char) |
| CILK_C_REDUCER_OPMUL_INSTANCE(unsigned char, uchar) |
| CILK_C_REDUCER_OPMUL_INSTANCE(signed char, schar) |
| CILK_C_REDUCER_OPMUL_INSTANCE(wchar_t, wchar_t) |
| CILK_C_REDUCER_OPMUL_INSTANCE(short, short) |
| CILK_C_REDUCER_OPMUL_INSTANCE(unsigned short, ushort) |
| CILK_C_REDUCER_OPMUL_INSTANCE(int, int) |
| CILK_C_REDUCER_OPMUL_INSTANCE(unsigned int, uint) |
| CILK_C_REDUCER_OPMUL_INSTANCE(unsigned int, unsigned) /* alternate name */ |
| CILK_C_REDUCER_OPMUL_INSTANCE(long, long) |
| CILK_C_REDUCER_OPMUL_INSTANCE(unsigned long, ulong) |
| CILK_C_REDUCER_OPMUL_INSTANCE(long long, longlong) |
| CILK_C_REDUCER_OPMUL_INSTANCE(unsigned long long, ulonglong) |
| CILK_C_REDUCER_OPMUL_INSTANCE(float, float) |
| CILK_C_REDUCER_OPMUL_INSTANCE(double, double) |
| CILK_C_REDUCER_OPMUL_INSTANCE(long double, longdouble) |
| |
| //@endcond |
| |
| __CILKRTS_END_EXTERN_C |
| |
| //@} |
| |
| //@} |
| |
| #endif /* REDUCER_OPMUL_H_INCLUDED */ |
