text: // -*- mode: C++; c-indent-level: 4; c-basic-offset: 4; tab-width: 8 -*-
  
  // this version expands convolve8_cpp by making Vec mimic the structure of
  // NumericVector. It peforms well, so this is is not the structure of
  // NumericVector that is the problem. So what is it then ?
  //
  // could it be because NumericVector is in a different library than
  // this code, so that operator[] is not inlined ?
  //
  // clues:
  // - http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.faqs/ka3538.html
  
  #include <Rcpp.h>
  
  #include "convolve10_cpp.h"
  
  RcppExport SEXP convolve10cpp(SEXP a, SEXP b){
      Rcpp::NumericVector xa(a);
      Rcpp::NumericVector xb(b);
      int n_xa = xa.size() ;
      int n_xb = xb.size() ;
      int nab = n_xa + n_xb - 1;
      Rcpp::NumericVector xab(nab);
  
      Vec vab(xab.begin()), va(xa.begin()), vb(xb.begin()) ;
  
      for (int i = 0; i < n_xa; i++)
          for (int j = 0; j < n_xb; j++)
              vab[i + j] += va[i] * vb[j];
  
      return xab ;
  }
  
  #include "loopmacro.h"
  LOOPMACRO_CPP(convolve10cpp)
  
  