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/* reducer_opadd.h -*- C++ -*-
*
* Copyright (C) 2009-2016, Intel Corporation
* All rights reserved.
*
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* modification, are permitted provided that the following conditions
* are met:
*
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* the documentation and/or other materials provided with the
* distribution.
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* POSSIBILITY OF SUCH DAMAGE.
*
* *********************************************************************
*
* PLEASE NOTE: This file is a downstream copy of a file mainitained in
* a repository at cilkplus.org. Changes made to this file that are not
* submitted through the contribution process detailed at
* http://www.cilkplus.org/submit-cilk-contribution will be lost the next
* time that a new version is released. Changes only submitted to the
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* not tracked.
*
* We welcome your contributions to this open source project. Thank you
* for your assistance in helping us improve Cilk Plus.
*/
/** @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 "Intel(R) Cilk(TM) Plus 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:
///@{
/** Adds or subtracts 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) {}
/** Reduces the views of two strands.
*
* 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.
*/
///@{
/** Increments the accumulator variable by @a x.
*/
op_add_view& operator+=(const Type& x) { this->m_value += x; return *this; }
/** Decrements 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-increments.
*
* @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-decrements.
*/
op_add_view& operator--() { --this->m_value; return *this; }
/** Post-decrements.
*
* @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--; }
/** Creates an object representing `*this + x`.
*
* @see rhs_proxy
*/
rhs_proxy operator+(const Type& x) const { return rhs_proxy(this, x); }
/** Creates an object representing `*this - x`.
*
* @see rhs_proxy
*/
rhs_proxy operator-(const Type& x) const { return rhs_proxy(this, -x); }
/** Assigns 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 Intel Cilk Plus library 1.0
* behavior). If `true`, reducers instantiated on this monoid
* will be cache-aligned for binary compatibility with
* reducers in Intel Cilk Plus 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 Intel Cilk Plus 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
/** Declares 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)
/** Declares 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
/** Declares 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);
/** Defines 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 Declares or defines 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
///@}
/* Declares or defines 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 */