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Edit File: reducer_opadd.h
/* reducer_opadd.h -*- C++ -*- * * @copyright * Copyright (C) 2009-2013, Intel Corporation * All rights reserved. * * @copyright * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * * * Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * * Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in * the documentation and/or other materials provided with the * distribution. * * Neither the name of Intel Corporation nor the names of its * contributors may be used to endorse or promote products derived * from this software without specific prior written permission. * * @copyright * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY * WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. */ /** @file reducer_opadd.h * * @brief Defines classes for doing parallel addition reductions. * * @ingroup ReducersAdd * * @see ReducersAdd */ #ifndef REDUCER_OPADD_H_INCLUDED #define REDUCER_OPADD_H_INCLUDED #include <cilk/reducer.h> /** @defgroup ReducersAdd Addition Reducers * * Addition reducers allow the computation of the sum 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 redopadd_usage Usage Example * * cilk::reducer< cilk::op_add<int> > r; * cilk_for (int i = 0; i != N; ++i) { * *r += a[i]; * } * return r.get_value(); * * @section redopadd_monoid The Monoid * * @subsection redopadd_monoid_values Value Set * * The value set of an addition 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 redopadd_monoid_operator Operator * * The operator of an addition reducer is the addition operator, defined by * the “`+`” binary operator on `Type`. * * @subsection redopadd_monoid_identity Identity * * The identity value of the reducer is the numeric value “`0`”. This is * expected to be the value of the default constructor `Type()`. * * @section redopadd_operations Operations * * @subsection redopadd_constructors Constructors * * reducer() // identity * reducer(const Type& value) * reducer(move_in(Type& variable)) * * @subsection redopadd_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 redopadd_initial Initial Values * * If an addition 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 redopadd_types. * * @subsection redopadd_view_ops View Operations * * *r += a * *r -= a * ++*r * --*r * (*r)++ * (*r)-- * *r = *r + a * *r = *r - a * *r = *r ± a1 ± a2 … ± an * * The post-increment and post-decrement operations do not return a value. (If * they did, they would expose the value contained in the view, which is * non-deterministic in the middle of a reduction.) * * Note that subtraction operations are allowed on an addition reducer because * subtraction is equivalent to addition with a negated operand. It is true * that `(x - y) - z` is not equivalent to `x - (y - z)`, but * `(x + (-y)) + (-z)` _is_ equivalent to `x + ((-y) + (-z))`. * * @section redopadd_floating_point Issues with Floating-Point Types * * Because of precision and round-off issues, floating-point addition is not * really associative. For example, `(1e30 + -1e30) + 1 == 1`, but * `1e30 + (-1e30 + 1) == 0`. * * In many cases, this won’t matter, but computations which have been * carefully ordered to control round-off errors 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 redopadd_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`. In addition, if the code uses the “`-=`”, * pre-increment, post-increment, pre-decrement, or post-decrement operators, * then the corresponding operators must be defined on `Type`. * * The expression `Type()` must be a valid expression which yields the * identity value (the value of `Type` whose numeric value is zero). * * @section redopadd_in_c Addition Reducers in C * * The @ref CILK_C_REDUCER_OPADD and @ref CILK_C_REDUCER_OPADD_TYPE macros can * be used to do addition reductions in C. For example: * * CILK_C_REDUCER_OPADD(r, double, 0); * 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 sum of the elements of a is %f\n", REDUCER_VIEW(r)); * * See @ref reducers_c_predefined. */ #ifdef __cplusplus namespace cilk { /** The addition reducer view class. * * This is the view class for reducers created with * `cilk::reducer< cilk::op_add<Type> >`. It holds the accumulator variable * for the reduction, and allows only addition and subtraction 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_add 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 ReducersAdd * @see op_add * * @ingroup ReducersAdd */ template <typename Type> class op_add_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_add_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_add_view are * ones which generate an rhs_proxy — that is, expressions of the form * `op_add_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_add_view */ class rhs_proxy { friend class op_add_view; const op_add_view* m_view; Type m_value; // Constructor is invoked only from op_add_view::operator+() and // op_add_view::operator-(). // rhs_proxy(const op_add_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: //@{ /** Add or subtract an additional rhs value. If `v` is an op_add_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; } rhs_proxy& operator-(const Type& x) { m_value -= x; return *this; } //@} }; /** Default/identity constructor. This constructor initializes the * contained value to `Type()`, which is expected to be the identity value * for addition on `Type`. */ op_add_view() : base() {} /** Construct with a specified initial value. */ explicit op_add_view(const Type& v) : base(v) {} /** Reduction operation. * * This function is invoked by the @ref op_add monoid to combine the views * of two strands when the right strand merges with the left one. It adds * the value contained in the right-strand view to the value contained in * the left-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_add monoid to implement the monoid * reduce operation. */ void reduce(op_add_view* right) { this->m_value += right->m_value; } /** @name Accumulator variable updates. * * These functions support the various syntaxes for incrementing or * decrementing the accumulator variable contained in the view. */ //@{ /** Increment the accumulator variable by @a x. */ op_add_view& operator+=(const Type& x) { this->m_value += x; return *this; } /** Decrement the accumulator variable by @a x. */ op_add_view& operator-=(const Type& x) { this->m_value -= x; return *this; } /** Pre-increment. */ op_add_view& operator++() { ++this->m_value; return *this; } /** Post-increment. * * @note Conventionally, post-increment operators return the old value * of the incremented variable. However, reducer views do not * expose their contained values, so `view++` does not have a * return value. */ void operator++(int) { this->m_value++; } /** Pre-decrement. */ op_add_view& operator--() { --this->m_value; return *this; } /** Post-decrement. * * @note Conventionally, post-decrement operators return the old value * of the decremented variable. However, reducer views do not * expose their contained values, so `view--` does not have a * return value. */ void operator--(int) { this->m_value--; } /** Create an object representing `*this + x`. * * @see rhs_proxy */ rhs_proxy operator+(const Type& x) const { return rhs_proxy(this, x); } /** 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_add_view& operator=(const rhs_proxy& rhs) { __CILKRTS_ASSERT(this == rhs.m_view); this->m_value += rhs.m_value; return *this; } //@} }; /** Monoid class for addition reductions. Instantiate the cilk::reducer * template class with an op_add monoid to create an addition reducer class. * For example, to compute * the sum of a set of `int` values: * * cilk::reducer< cilk::op_add<int> > r; * * @tparam Type The reducer value type. * @tparam Align If `false` (the default), reducers instantiated on this * monoid will be naturally aligned (the Cilk library 1.0 * behavior). If `true`, reducers instantiated on this monoid * will be cache-aligned for binary compatibility with * reducers in Cilk library version 0.9. * * @see ReducersAdd * @see op_add_view * * @ingroup ReducersAdd */ template <typename Type, bool Align = false> struct op_add : public monoid_with_view<op_add_view<Type>, Align> {}; /** **Deprecated** addition reducer wrapper class. * * reducer_opadd is the same as @ref reducer<@ref op_add>, except that * reducer_opadd is a proxy for the contained view, so that accumulator * variable update operations can be applied directly to the reducer. For * example, a value is added to a `reducer<%op_add>` with `*r += a`, but a * value can be added to a `%reducer_opadd` with `r += a`. * * @deprecated Users are strongly encouraged to use `reducer<monoid>` * reducers rather than the old wrappers like reducer_opadd. * The `reducer<monoid>` reducers show the reducer/monoid/view * architecture more clearly, are more consistent in their * implementation, and present a simpler model for new * user-implemented reducers. * * @note Implicit conversions are provided between `%reducer_opadd` * and `reducer<%op_add>`. This allows incremental code * conversion: old code that used `%reducer_opadd` can pass a * `%reducer_opadd` to a converted function that now expects a * pointer or reference to a `reducer<%op_add>`, and vice * versa. * * @tparam Type The value type of the reducer. * * @see op_add * @see reducer * @see ReducersAdd * * @ingroup ReducersAdd */ template <typename Type> class reducer_opadd : public reducer< op_add<Type, true> > { typedef reducer< op_add<Type, true> > base; using base::view; public: /// The view type for the reducer. typedef typename base::view_type view_type; /// The view’s rhs proxy type. typedef typename view_type::rhs_proxy rhs_proxy; /// The view type for the reducer. typedef view_type View; /// The monoid type for the reducer. typedef typename base::monoid_type Monoid; /** @name Constructors */ //@{ /** Default (identity) constructor. * * Constructs the wrapper with the default initial value of `Type()`. */ reducer_opadd() {} /** Value constructor. * * Constructs the wrapper with a specified initial value. */ explicit reducer_opadd(const Type& initial_value) : base(initial_value) {} //@} /** @name Forwarded functions * @details Functions that update the contained accumulator variable are * simply forwarded to the contained @ref op_add_view. */ //@{ /// @copydoc op_add_view::operator+=(const Type&) reducer_opadd& operator+=(const Type& x) { view() += x; return *this; } /// @copydoc op_add_view::operator-=(const Type&) reducer_opadd& operator-=(const Type& x) { view() -= x; return *this; } /// @copydoc op_add_view::operator++() reducer_opadd& operator++() { ++view(); return *this; } /// @copydoc op_add_view::operator++(int) void operator++(int) { view()++; } /// @copydoc op_add_view::operator-\-() reducer_opadd& operator--() { --view(); return *this; } /// @copydoc op_add_view::operator-\-(int) void operator--(int) { view()--; } // The legacy definitions of reducer_opadd::operator+() and // reducer_opadd::operator-() have different behavior and a different // return type than this definition. The legacy version is defined as a // member function, so this new version is defined as a free function to // give it a different signature, so that they won’t end up sharing a // single object file entry. /// @copydoc op_add_view::operator+(const Type&) const friend rhs_proxy operator+(const reducer_opadd& r, const Type& x) { return r.view() + x; } /// @copydoc op_add_view::operator-(const Type&) const friend rhs_proxy operator-(const reducer_opadd& r, const Type& x) { return r.view() - x; } /// @copydoc op_add_view::operator=(const rhs_proxy&) reducer_opadd& operator=(const rhs_proxy& temp) { view() = temp; return *this; } //@} /** @name Dereference * @details Dereferencing a wrapper is a no-op. It simply returns the * wrapper. Combined with the rule that the wrapper forwards view * operations to its contained view, this means that view operations can * be written the same way on reducers and wrappers, which is convenient * for incrementally converting old code using wrappers to use reducers * instead. That is: * * reducer< op_add<int> > r; * *r += a; // *r returns the view * // operator += is a view member function * * reducer_opadd<int> w; * *w += a; // *w returns the wrapper * // operator += is a wrapper member function that * // calls the corresponding view function */ //@{ reducer_opadd& operator*() { return *this; } reducer_opadd const& operator*() const { return *this; } reducer_opadd* operator->() { return this; } reducer_opadd const* operator->() const { return this; } //@} /** @name Upcast * @details In Cilk library 0.9, reducers were always cache-aligned. In * library 1.0, reducer cache alignment is optional. By default, reducers * are unaligned (i.e., just naturally aligned), but legacy wrappers * inherit from cache-aligned reducers for binary compatibility. * * This means that a wrapper will automatically be upcast to its aligned * reducer base class. The following conversion operators provide * pseudo-upcasts to the corresponding unaligned reducer class. */ //@{ operator reducer< op_add<Type, false> >& () { return *reinterpret_cast< reducer< op_add<Type, false> >* >(this); } operator const reducer< op_add<Type, false> >& () const { return *reinterpret_cast< const reducer< op_add<Type, false> >* >(this); } //@} }; /// @cond internal /** Metafunction specialization for reducer conversion. * * This specialization of the @ref legacy_reducer_downcast template class * defined in reducer.h causes the `reducer< op_add<Type> >` class to have an * `operator reducer_opadd<Type>& ()` conversion operator that statically * downcasts the `reducer<op_add>` to the corresponding `reducer_opadd` type. * (The reverse conversion, from `reducer_opadd` to `reducer<op_add>`, is just * an upcast, which is provided for free by the language.) * * @ingroup ReducersAdd */ template <typename Type, bool Align> struct legacy_reducer_downcast<reducer<op_add<Type, Align> > > { typedef reducer_opadd<Type> type; }; /// @endcond } // namespace cilk #endif // __cplusplus /** @ingroup ReducersAdd */ //@{ /** @name C Language Reducer Macros * * These macros are used to declare and work with numeric op_add reducers in * C code. * * @see @ref page_reducers_in_c */ //@{ __CILKRTS_BEGIN_EXTERN_C /** Opadd reducer type name. * * This macro expands into the identifier which is the name of the op_add * 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 ReducersAdd */ #define CILK_C_REDUCER_OPADD_TYPE(tn) \ __CILKRTS_MKIDENT(cilk_c_reducer_opadd_,tn) /** Declare an op_add reducer object. * * This macro expands into a declaration of an op_add reducer object for a * specified numeric type. For example: * * CILK_C_REDUCER_OPADD(my_reducer, double, 0.0); * * @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 ReducersAdd */ #define CILK_C_REDUCER_OPADD(obj,tn,v) \ CILK_C_REDUCER_OPADD_TYPE(tn) obj = \ CILK_C_INIT_REDUCER(_Typeof(obj.value), \ __CILKRTS_MKIDENT(cilk_c_reducer_opadd_reduce_,tn), \ __CILKRTS_MKIDENT(cilk_c_reducer_opadd_identity_,tn), \ __cilkrts_hyperobject_noop_destroy, v) /// @cond internal /** Declare the op_add reducer functions for a numeric type. * * This macro expands into external function declarations for functions which * implement the reducer functionality for the op_add 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_OPADD_DECLARATION(t,tn) \ typedef CILK_C_DECLARE_REDUCER(t) CILK_C_REDUCER_OPADD_TYPE(tn); \ __CILKRTS_DECLARE_REDUCER_REDUCE(cilk_c_reducer_opadd,tn,l,r); \ __CILKRTS_DECLARE_REDUCER_IDENTITY(cilk_c_reducer_opadd,tn); /** Define the op_add reducer functions for a numeric type. * * This macro expands into function definitions for functions which implement * the reducer functionality for the op_add 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_OPADD_DEFINITION(t,tn) \ typedef CILK_C_DECLARE_REDUCER(t) CILK_C_REDUCER_OPADD_TYPE(tn); \ __CILKRTS_DECLARE_REDUCER_REDUCE(cilk_c_reducer_opadd,tn,l,r) \ { *(t*)l += *(t*)r; } \ __CILKRTS_DECLARE_REDUCER_IDENTITY(cilk_c_reducer_opadd,tn) \ { *(t*)v = 0; } //@{ /** @def CILK_C_REDUCER_OPADD_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_OPADD_INSTANCE(t,tn) \ CILK_C_REDUCER_OPADD_DEFINITION(t,tn) #else # define CILK_C_REDUCER_OPADD_INSTANCE(t,tn) \ CILK_C_REDUCER_OPADD_DECLARATION(t,tn) #endif //@} /* Declare or define an instance of the reducer type and its functions for each * numeric type. */ CILK_C_REDUCER_OPADD_INSTANCE(char, char) CILK_C_REDUCER_OPADD_INSTANCE(unsigned char, uchar) CILK_C_REDUCER_OPADD_INSTANCE(signed char, schar) CILK_C_REDUCER_OPADD_INSTANCE(wchar_t, wchar_t) CILK_C_REDUCER_OPADD_INSTANCE(short, short) CILK_C_REDUCER_OPADD_INSTANCE(unsigned short, ushort) CILK_C_REDUCER_OPADD_INSTANCE(int, int) CILK_C_REDUCER_OPADD_INSTANCE(unsigned int, uint) CILK_C_REDUCER_OPADD_INSTANCE(unsigned int, unsigned) /* alternate name */ CILK_C_REDUCER_OPADD_INSTANCE(long, long) CILK_C_REDUCER_OPADD_INSTANCE(unsigned long, ulong) CILK_C_REDUCER_OPADD_INSTANCE(long long, longlong) CILK_C_REDUCER_OPADD_INSTANCE(unsigned long long, ulonglong) CILK_C_REDUCER_OPADD_INSTANCE(float, float) CILK_C_REDUCER_OPADD_INSTANCE(double, double) CILK_C_REDUCER_OPADD_INSTANCE(long double, longdouble) //@endcond __CILKRTS_END_EXTERN_C //@} //@} #endif /* REDUCER_OPADD_H_INCLUDED */