1 // -*- mode: C++; c-indent-level: 4; c-basic-offset: 4; tab-width: 8 -*-
2 
3 // this version expands convolve8_cpp by making Vec mimic the structure of
4 // NumericVector. It peforms well, so this is is not the structure of
5 // NumericVector that is the problem. So what is it then ?
6 //
7 // could it be because NumericVector is in a different library than
8 // this code, so that operator[] is not inlined ?
9 //
10 // clues:
11 // - http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka3538.html
12 
13 #include <Rcpp.h>
14 
15 class Cache{
16 public:
17     typedef double& proxy ;
18     typedef double* iterator ;
19 
Cache(iterator data_)20     Cache( iterator data_) : data(data_){}
21 
ref(int i)22     inline proxy ref(int i){ return data[i] ; }
ref(int i) const23     inline proxy ref(int i) const { return data[i] ; }
24 
25 private:
26     iterator data ;
27 } ;
28 
29 class Vec {
30 public:
31     typedef double& proxy ;
32 
Vec(double * data_)33     Vec( double* data_ ) : cache(data_){}
operator [](int i)34     inline proxy operator[]( int i){ return cache.ref(i) ; }
operator [](int i) const35     inline proxy operator[]( int i) const { return cache.ref(i) ; }
36 
37 private:
38     Cache cache ;
39 } ;
40 
41 
convolve9cpp(SEXP a,SEXP b)42 RcppExport SEXP convolve9cpp(SEXP a, SEXP b){
43     Rcpp::NumericVector xa(a);
44     Rcpp::NumericVector xb(b);
45     int n_xa = xa.size() ;
46     int n_xb = xb.size() ;
47     int nab = n_xa + n_xb - 1;
48     Rcpp::NumericVector xab(nab);
49 
50     Vec vab(xab.begin()), va(xa.begin()), vb(xb.begin()) ;
51 
52     for (int i = 0; i < n_xa; i++)
53         for (int j = 0; j < n_xb; j++)
54             vab[i + j] += va[i] * vb[j];
55 
56     return xab ;
57 }
58 
59 #include "loopmacro.h"
60 LOOPMACRO_CPP(convolve9cpp)
61 
62