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*
* @copyright
* Copyright (C) 2012-2013, 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_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 */
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