amroc/hds/IndexGridData1.h

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// -*- C++ -*-

#ifndef _included_IndexGridData1_h
#define _included_IndexGridData1_h

#include "generic.h"

/*
*************************************************************************
*                                                                       *
* Define some looping constructs for GridData.  Note that these will    *
* take either an array or a region as the second argument.              *
*                                                                       *
* Copy the region extents into a local constant integer to aid the      *
* compiler in doing some loop optimizations.                            *
*                                                                       *
*************************************************************************
*/

#ifndef for_1
#define for_1(i, r, s) {                                                \
   const int name2(i,_L) = (((r).lower(0)+((r).lower(0)<0?-s(0)+1:s(0)-1))/s(0))*s(0);      \
   const int name2(i,_U) = (r).upper(0);                                \
   const int name2(si,_S) = (s(0));                                     \
   for (register int i = name2(i,_L); i <= name2(i,_U); i+=name2(si,_S)) {
#endif
#ifndef end_for
#define end_for } }
#endif

/*
*************************************************************************
*                                                                       *
* These macros provide simple access to ``fast indexing'' from C++.     *
* Current C++ compilers do not do a good job of optimizing C++ loops    *
* with array access.  Using these macros should speed up loops by a     *
* factor of about three.  Note that we still use the Fortran indexing   *
* convention.                                                           *
*                                                                       *
* These macros should be used as follows:                               *
*                                                                       *
*       BeginFastIndex1(a, double);                                     *
*       for_1(i, a)                                                     *
*          FastIndex1(a, i) = 0.0;                                      *
*       end_for                                                         *
*       EndFastIndex1(a);                                               *
*                                                                       *
*************************************************************************
*/

#ifndef BeginFastIndex1
#define BeginFastIndex1(a, b, d, type) {                                \
const int   name2(a,_B)  = b.bottom();                                  \
type *const name2(a,_D)  = d;                                           \
const int   name2(a,_s0) = b.stepsize(0)
#define FastIndex1(a, i)                                                \
name2(a,_D)[name2(a,_B)+((i)/name2(a,_s0))]
#define EndFastIndex1(a) }
#endif

#endif

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