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Found 2 results

1. ## Floating Point Steps

So I have a serious question. Does LabVIEW have a way (built in or library) of calculating the next larger or next smaller floating point value. C standard library "math.h" has two functions: nextafter, and nexttowards. I have put together a c function: that seems to do the trick nicely for single floats (well only for stepup): #include <math.h> #include <stdint.h> uint32_t nextUpFloat(uint32_t v){ uint32_t sign; = v&0x80000000; if (v==0x80000000||v==0){ //For zero and neg zero return 1; } if ((v>=0x7F800000 && v<0x80000000)||(v>0xff800000)){ //Check for Inf and NAN return v; //no higher value in these cases. } sign = v&0x80000000; //Get sign bit v&=0x7FFFFFFF; //strip sign bit if(sign==0){ v++; }else{ v--; } v=v|sign; //re merge sign return v; } I could put this in labVIEW, but these things are tricky and there are some unexpected cases. So its always better to use a reference.
2. ## Floating point almost equal

The other day I encountered a situation where I wanted to test if two floating point values were equal. Of course, one of the first things that you are told about floating point values is that you should never test for exact equality. So I proceed to wire up: Is X = Y +/- some acceptable tolerance? And that worked perfectly for my use case. That is, I knew that the max. value was 1000 and the min value was 0 and the resolution (or increment) was 0.01. A tolerance of 0.001 was sufficient. This got me thinking. Wouldn't it be nice to have some reusable VIs for testing if floating point values are almost equal? Unfortunately this meant taking a broader view of the problem and lead me to this interesting blog post: http://randomascii.wordpress.com/2012/02/25/comparing-floating-point-numbers-2012-edition/ I've attached VIs for the Absolute Epsilon comparison, Relative Epsilon comparison and the ULP comparison described in the blog post for double precision floating point values. Perhaps this would be a nice addition to the somewhat barren OpenG Comparison Pallet? Uploaded package to Code Repository: http://lavag.org/files/file/259-floating-point-almost-equal/ AlmostEqual_LV2013.zip AlmostEqual_LV86.zip
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