Hey Christian, Thanks very much for the great reply! Will do some more testing and post my results hopefully sometime next week.
Jeff On Fri, Sep 16, 2011 at 11:18 PM, Christian Gunning <x...@unm.edu> wrote: > Jeff, > > A few random comments in addition to Dirk's sound advice: > > 1. I recommend using bigger matrices for testing just to get a feel. > For testing loop speed, you want the proportion of loop time to be > *very high* compared to the R interpreter overhead, resolution of your > timer, etc. Here, the extra as<arma::mat> and wrap() in armaSrc may > add appreciable execution time relative to the loop work -- only > testing will tell :) > > 2. Another advantage of big matrices is testing the relative impact > of memory copying versus in-place modification. Both Rcpp and > RcppArmadillo allow for both -- for the former, search the quickref > for "clone" for an intro. With RcppArmadillo, in-place is a little > more involved, but look for this line: > "However, if copy_aux_mem is set to false, the matrix will instead > directly use the auxiliary memory (ie. no copying). This is faster, > but can be dangerous unless you know what you're doing!" > http://arma.sourceforge.net/docs.html#Mat > > 3. I've modified the below to move the +op from the conditional > evaluation to the definition. For small thetaEndIndex or simple ops, > this won't matter, but for theatEndIndex = 1e12 and something like a > vec.size() accessor, it can make a noticeable difference. In general, > it's a good habit not to put ops in the conditional unless you really > need them. > > > armaSrc <- ' > ... > > int thetaEndIndex = as<int>(sthetaEndIndex) - 1; > ... > > for (int i = thetaStartIndex + 1; i <= thetaEndIndex; i++) { > > best, > Christian > > -- > A man, a plan, a cat, a ham, a yak, a yam, a hat, a canal – Panama! >
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