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reduce.h

/***************************************************************************
 * blitz/array/reduce.h   Reductions of an array (or array expression) in a 
 *                        single rank: sum, mean, min, minIndex, max, maxIndex, 
 *                        product, count, any, all
 *
 * $Id: reduce.h,v 1.2 2002/09/12 07:02:06 eric Exp $
 *
 * Copyright (C) 1997-2001 Todd Veldhuizen <tveldhui@oonumerics.org>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version 2
 * of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * Suggestions:          blitz-dev@oonumerics.org
 * Bugs:                 blitz-bugs@oonumerics.org
 *
 * For more information, please see the Blitz++ Home Page:
 *    http://oonumerics.org/blitz/
 *
 ***************************************************************************
 * $Log: reduce.h,v $
 * Revision 1.2  2002/09/12 07:02:06  eric
 * major rewrite of weave.
 *
 * 0.
 * The underlying library code is significantly re-factored and simpler. There used to be a xxx_spec.py and xxx_info.py file for every group of type conversion classes.  The spec file held the python code that handled the conversion and the info file had most of the C code templates that were generated.  This proved pretty confusing in practice, so the two files have mostly been merged into the spec file.
 *
 * Also, there was quite a bit of code duplication running around.  The re-factoring was able to trim the standard conversion code base (excluding blitz and accelerate stuff) by about 40%.  This should be a huge maintainability and extensibility win.
 *
 * 1.
 * With multiple months of using Numeric arrays, I've found some of weave's "magic variable" names unwieldy and want to change them.  The following are the old declarations for an array x of Float32 type:
 *
 *         PyArrayObject* x = convert_to_numpy(...);
 *         float* x_data = (float*) x->data;
 *         int*   _Nx = x->dimensions;
 *         int*   _Sx = x->strides;
 *         int    _Dx = x->nd;
 *
 * The new declaration looks like this:
 *
 *         PyArrayObject* x_array = convert_to_numpy(...);
 *         float* x = (float*) x->data;
 *         int*   Nx = x->dimensions;
 *         int*   Sx = x->strides;
 *         int    Dx = x->nd;
 *
 * This is obviously not backward compatible, and will break some code (including a lot of mine).  It also makes inline() code more readable and natural to write.
 *
 * 2.
 * I've switched from CXX to Gordon McMillan's SCXX for list, tuples, and dictionaries.  I like CXX pretty well, but its use of advanced C++ (templates, etc.) caused some portability problems.  The SCXX library is similar to CXX but doesn't use templates at all.  This, like (1) is not an
 * API compatible change and requires repairing existing code.
 *
 * I have also thought about boost python, but it also makes heavy use of templates.  Moving to SCXX gets rid of almost all template usage for the standard type converters which should help portability.  std::complex and std::string from the STL are the only templates left.  Of course blitz still uses templates in a major way so weave.blitz will continue to be hard on compilers.
 *
 * I've actually considered scrapping the C++ classes for list, tuples, and
 * dictionaries, and just fall back to the standard Python C API because the classes are waaay slower than the raw API in many cases.  They are also more convenient and less error prone in many cases, so I've decided to stick with them.  The PyObject variable will always be made available for variable "x" under the name "py_x" for more speedy operations.  You'll definitely want to use these for anything that needs to be speedy.
 *
 * 3.
 * strings are converted to std::string now.  I found this to be the most useful type in for strings in my code.  Py::String was used previously.
 *
 * 4.
 * There are a number of reference count "errors" in some of the less tested conversion codes such as instance, module, etc.  I've cleaned most of these up.  I put errors in quotes here because I'm actually not positive that objects passed into "inline" really need reference counting applied to them.  The dictionaries passed in by inline() hold references to these objects so it doesn't seem that they could ever be garbage collected inadvertently.  Variables used by ext_tools, though, definitely need the reference counting done.  I don't think this is a major cost in speed, so it probably isn't worth getting rid of the ref count code.
 *
 * 5.
 * Unicode objects are now supported.  This was necessary to support rendering Unicode strings in the freetype wrappers for Chaco.
 *
 * 6.
 * blitz++ was upgraded to the latest CVS.  It compiles about twice as fast as the old blitz and looks like it supports a large number of compilers (though only gcc 2.95.3 is tested).  Compile times now take about 9 seconds on my 850 MHz PIII laptop.
 *
 * Revision 1.2  2001/01/24 20:22:51  tveldhui
 * Updated copyright date in headers.
 *
 * Revision 1.1.1.1  2000/06/19 12:26:14  tveldhui
 * Imported sources
 *
 * Revision 1.2  1998/03/14 00:04:47  tveldhui
 * 0.2-alpha-05
 *
 * Revision 1.1  1997/07/16 14:51:20  tveldhui
 * Update: Alpha release 0.2 (Arrays)
 *
 */

#ifndef BZ_ARRAYREDUCE_H
#define BZ_ARRAYREDUCE_H

#ifndef BZ_ARRAYEXPR_H
 #error <blitz/array/reduce.h> must be included after <blitz/array/expr.h>
#endif

#ifndef BZ_REDUCE_H
 #include <blitz/reduce.h>
#endif

BZ_NAMESPACE(blitz)

template<class T_expr, int N_index, class T_reduction>
class _bz_ArrayExprReduce {

public:   
    typedef _bz_typename T_reduction::T_numtype T_numtype;
    typedef T_expr      T_ctorArg1;
    typedef T_reduction T_ctorArg2;

    enum { numArrayOperands = BZ_ENUM_CAST(T_expr::numArrayOperands),
        numIndexPlaceholders = BZ_ENUM_CAST(T_expr::numIndexPlaceholders) + 1,
        rank = BZ_ENUM_CAST(T_expr::rank) - 1 };

    _bz_ArrayExprReduce(const _bz_ArrayExprReduce<T_expr,N_index,T_reduction>&
        reduce)
        : reduce_(reduce.reduce_), iter_(reduce.iter_)
    {
    }

    _bz_ArrayExprReduce(T_expr expr)
        : iter_(expr)
    { }

    _bz_ArrayExprReduce(T_expr expr, T_reduction reduce)
        : iter_(expr), reduce_(reduce)
    { }

    int ascending(int rank)
    { return iter_.ascending(rank); }

    int ordering(int rank)
    { return iter_.ordering(rank); }

    int lbound(int rank)
    { return iter_.lbound(rank); }

    int ubound(int rank)
    { return iter_.ubound(rank); }

    template<int N_destRank>
    T_numtype operator()(const TinyVector<int, N_destRank>& destIndex)
    {
        BZPRECHECK(N_destRank == N_index,  
            "Array reduction performed over rank " << N_index 
            << " to produce a rank " << N_destRank << " expression." << endl
            << "You must reduce over rank " << N_destRank << " instead.");

        TinyVector<int, N_destRank + 1> index;

        // This metaprogram copies elements 0..N-1 of destIndex into index
        _bz_meta_vecAssign<N_index, 0>::assign(index, destIndex, 
            _bz_update<int,int>());

        int lbound = iter_.lbound(N_index);
        int ubound = iter_.ubound(N_index);

        // NEEDS_WORK: replace with tiny(int()) and huge(int()) once
        // <limits> widely available
        BZPRECHECK((lbound != INT_MIN) && (ubound != INT_MAX),
           "Array reduction performed over rank " << N_index
           << " is unbounded." << endl 
           << "There must be an array object in the expression being reduced"
           << endl << "which provides a bound in rank " << N_index << ".");

        reduce_.reset();

        for (index[N_index] = iter_.lbound(N_index);
            index[N_index] <= ubound; ++index[N_index])
        {
            if (!reduce_(iter_(index), index[N_index]))
                break;
        }

        return reduce_.result(ubound-lbound+1);
    }

    // If you have a precondition failure on this routine, it means
    // you are trying to use stack iteration mode on an expression
    // which contains an index placeholder.  You must use index
    // iteration mode instead.
    int operator*()
    {
        BZPRECONDITION(0);
        return 0;
    }

    // See operator*() note
    void push(int)
    {
        BZPRECONDITION(0);
    }

    // See operator*() note
    void pop(int)
    {
        BZPRECONDITION(0);
    }

    // See operator*() note
    void advance()
    {
        BZPRECONDITION(0);
    }

    // See operator*() note
    void advance(int)
    {
        BZPRECONDITION(0);
    }

    // See operator*() note
    void loadStride(int)
    {
        BZPRECONDITION(0);
    }

    _bz_bool isUnitStride(int rank) const
    {
        BZPRECONDITION(0);
        return false;
    }

    void advanceUnitStride()
    {
        BZPRECONDITION(0);
    }

    _bz_bool canCollapse(int,int) const
    {   BZPRECONDITION(0); return _bz_false; }

    T_numtype operator[](int)
    {
        BZPRECONDITION(0);
        return T_numtype();
    }

    T_numtype fastRead(int)
    {
        BZPRECONDITION(0);
        return T_numtype();
    }

    int suggestStride(int) const
    {
        BZPRECONDITION(0);
        return 0;
    }

    _bz_bool isStride(int,int) const
    {
        BZPRECONDITION(0);
        return _bz_true;
    }

    template<int N_rank>
    void moveTo(const TinyVector<int,N_rank>& i)
    {
        BZPRECONDITION(0);
        return;
    }

    void prettyPrint(string& str, prettyPrintFormat& format) const
    {
        // NEEDS_WORK-- do real formatting for reductions
        str += "reduce[NEEDS_WORK](";
        iter_.prettyPrint(str,format);
        str += ")";
    }

    template<class T_shape>
    _bz_bool shapeCheck(const T_shape& shape) const
    { 
        // NEEDS_WORK-- do a real shape check (tricky)
        return _bz_true; 
    }

private: 
    _bz_ArrayExprReduce() { }

    T_reduction reduce_;
    T_expr iter_;
};

#define BZ_DECL_ARRAY_PARTIAL_REDUCE(fn,reduction)                      \
template<class T_expr, int N_index>                                     \
inline                                                                  \
_bz_ArrayExpr<_bz_ArrayExprReduce<_bz_ArrayExpr<T_expr>, N_index,       \
    reduction<_bz_typename T_expr::T_numtype> > >                       \
fn(_bz_ArrayExpr<T_expr> expr, const IndexPlaceholder<N_index>&)        \
{                                                                       \
    return _bz_ArrayExprReduce<_bz_ArrayExpr<T_expr>, N_index,          \
        reduction<_bz_typename T_expr::T_numtype> >(expr);              \
}                                                                       \
                                                                        \
template<class T_numtype, int N_rank, int N_index>                      \
inline                                                                  \
_bz_ArrayExpr<_bz_ArrayExprReduce<FastArrayIterator<T_numtype,N_rank>,  \
    N_index, reduction<T_numtype> > >                                   \
fn(const Array<T_numtype, N_rank>& array,                               \
    const IndexPlaceholder<N_index>&)                                   \
{                                                                       \
    return _bz_ArrayExprReduce<FastArrayIterator<T_numtype,N_rank>,     \
        N_index, reduction<T_numtype> > (array.beginFast());            \
}                        

BZ_DECL_ARRAY_PARTIAL_REDUCE(sum,      ReduceSum)
BZ_DECL_ARRAY_PARTIAL_REDUCE(mean,     ReduceMean)
BZ_DECL_ARRAY_PARTIAL_REDUCE(min,      ReduceMin)
BZ_DECL_ARRAY_PARTIAL_REDUCE(minIndex, ReduceMinIndex)
BZ_DECL_ARRAY_PARTIAL_REDUCE(max,      ReduceMax)
BZ_DECL_ARRAY_PARTIAL_REDUCE(maxIndex, ReduceMaxIndex)
BZ_DECL_ARRAY_PARTIAL_REDUCE(product,  ReduceProduct)
BZ_DECL_ARRAY_PARTIAL_REDUCE(count,    ReduceCount)
BZ_DECL_ARRAY_PARTIAL_REDUCE(any,      ReduceAny)
BZ_DECL_ARRAY_PARTIAL_REDUCE(all,      ReduceAll)
BZ_DECL_ARRAY_PARTIAL_REDUCE(first,    ReduceFirst)
BZ_DECL_ARRAY_PARTIAL_REDUCE(last,     ReduceLast)

/*
 * Complete reductions
 */

// Prototype of reduction function
template<class T_expr, class T_reduction>
_bz_typename T_reduction::T_resulttype
_bz_ArrayExprFullReduce(T_expr expr, T_reduction reduction);

#define BZ_DECL_ARRAY_FULL_REDUCE(fn,reduction)                         \
template<class T_expr>                                                  \
inline                                                                  \
_bz_typename reduction<_bz_typename T_expr::T_numtype>::T_resulttype    \
fn(_bz_ArrayExpr<T_expr> expr)                                          \
{                                                                       \
    return _bz_ArrayExprFullReduce(expr,                                \
        reduction<_bz_typename T_expr::T_numtype>());                   \
}                                                                       \
                                                                        \
template<class T_numtype, int N_rank>                                   \
inline                                                                  \
_bz_typename reduction<T_numtype>::T_resulttype                         \
fn(const Array<T_numtype, N_rank>& array)                               \
{                                                                       \
    return _bz_ArrayExprFullReduce(array.beginFast(),                   \
        reduction<T_numtype>());                                        \
}                                                                     

BZ_DECL_ARRAY_FULL_REDUCE(sum,      ReduceSum)
BZ_DECL_ARRAY_FULL_REDUCE(mean,     ReduceMean)
BZ_DECL_ARRAY_FULL_REDUCE(min,      ReduceMin)
BZ_DECL_ARRAY_FULL_REDUCE(max,      ReduceMax)
BZ_DECL_ARRAY_FULL_REDUCE(product,  ReduceProduct)
BZ_DECL_ARRAY_FULL_REDUCE(count,    ReduceCount)
BZ_DECL_ARRAY_FULL_REDUCE(any,      ReduceAny)
BZ_DECL_ARRAY_FULL_REDUCE(all,      ReduceAll)
BZ_DECL_ARRAY_FULL_REDUCE(first,    ReduceFirst)
BZ_DECL_ARRAY_FULL_REDUCE(last,     ReduceLast)

// Special versions of complete reductions: minIndex and
// maxIndex

#define BZ_DECL_ARRAY_FULL_REDUCE_INDEXVECTOR(fn,reduction)             \
template<class T_expr>                                                  \
inline                                                                  \
_bz_typename reduction<_bz_typename T_expr::T_numtype,                  \
    T_expr::rank>::T_resulttype                                         \
fn(_bz_ArrayExpr<T_expr> expr)                                          \
{                                                                       \
    return _bz_reduceWithIndexVectorTraversal(expr,                     \
        reduction<_bz_typename T_expr::T_numtype, T_expr::rank>());     \
}                                                                       \
                                                                        \
template<class T_numtype, int N_rank>                                   \
inline                                                                  \
_bz_typename reduction<T_numtype,N_rank>::T_resulttype                  \
fn(const Array<T_numtype, N_rank>& array)                               \
{                                                                       \
    return _bz_reduceWithIndexVectorTraversal( array.beginFast(),       \
        reduction<T_numtype,N_rank>());                                 \
}

BZ_DECL_ARRAY_FULL_REDUCE_INDEXVECTOR(minIndex, ReduceMinIndexVector)
BZ_DECL_ARRAY_FULL_REDUCE_INDEXVECTOR(maxIndex, ReduceMaxIndexVector)

BZ_NAMESPACE_END

#include <blitz/array/reduce.cc>

#endif // BZ_ARRAYREDUCE_H

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