[R] Was Logical inconsistency - algorithm portability

John C Nash nashjc at uottawa.ca
Tue Dec 9 18:36:55 CET 2008

The "logical inconsistency" thread has wandered a bit and discussion now veers towards portability of algorithms. On that subject, I have off-list been sharing ideas about the existence of functions to ensure optimizing compilers do not corrupt logical tests in numerical methods. Apparently the "volatile" adjective may have a role here (I am generally a "visiting programmer" in C, doing just enough to get things to work, and cribbing other folks' code). 

One need is for a function that ensures the stored representation of numbers is returned, call it "STORED", so that one can test if STORED(x) == STORED(y). Various hacks can do this. One time we used an array of length 2. But hacks are generally ugly and vulnerable to updates in compilers, so a properly written and documented function would be helpful. And, of course, may already exist. 

As this is not a short-term help request but a long term need, I suggest contacting me off list about this subject.


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