Dear List,
I wonder if there is a way to convert a big matrix to ‘float’ instead of
‘double’ within a Rcpp program. The reason for using float is mainly for
performance improvement.
For instance, I have a simple function named ‘print_bigmat’ as shown below.
As shown in the output, ‘double_bigmat' will save the correct values of the
original matrix ‘x’ but not ‘float_bigmat’.
// [[Rcpp::export]]
int print_bigmat(SEXP pBigMat) {
XPtr<BigMatrix> xpMat(pBigMat);
const mat& double_bigmat = arma::Mat<double>((double *)xpMat->matrix(),
xpMat->nrow(), xpMat->ncol(), false);
const fmat& float_bigmat = arma::Mat<float>((float *)xpMat->matrix(),
xpMat->nrow(), xpMat->ncol(), false);
Rcout << double_bigmat << endl;
Rcout << float_bigmat << endl;
return 0;
}
Output:
> x <- matrix(rnorm(10), nrow=2)
> x
[,1] [,2] [,3] [,4] [,5]
[1,] -0.05514382 -0.03943825 1.4145593 -0.1161918 2.3282466
[2,] -1.22023371 -0.35592125 0.7714512 0.6865120 -0.3504811
> print_bigmat(as.big.matrix(x)@address)
-0.0551 -0.0394 1.4146 -0.1162 2.3282
-1.2202 -0.3559 0.7715 0.6865 -0.3505
-3.3865e-14 -8.6552e+04 4.5441e-07 -5.0912e+23 -1.5184e+34
-1.3456e+00 -1.9025e+00 -1.2828e+00 -1.6780e+00 1.9268e+00
[1] 0
>
Thanks much,
Yue
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