Thanks, Tim, It appeares that you were right. The reason was in usage of "fmax" function during comparision in "if" statement which apparently uses floats and not doubles. It seems that by including code line with 'if(fmax(a,b)>0)' i got both 'a' and 'b' accidently converted to floats. This is something done inside impala and not in g++ compiler. So everything was correct in 'g++' and in impala I received precision error because of floats. I decided to implicitly convert all values from 'DoubleVal' to 'long double' and to add additional full references to every function from std that I've used (like std::max()). That've solved my issues.
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