Brian S. McCormick created MATH-1386:
Summary: EPSILON value in org.apache.commons.math.util.MathUtils
seems like half of what it should be
Project: Commons Math
Issue Type: Bug
Environment: win 7
Reporter: Brian S. McCormick
I've always used 1.1920929E-7 for dealing with float epsilon values. When
dealing with double I've always used 2.220446049250313E-16 for epsilon.
You have it defined in org.apache.commons.math.util.MathUtils as
1.1102230246251565E-16 which is half what I think it should be.
I come up with these numbers using the following:
float fEps = Float.intBitsToFloat(Float.floatToIntBits(1f) + 1) - 1;
double dEps = Double.longBitsToDouble(Double.doubleToLongBits(1) + 1) - 1;
Am I correct? I don't really know. I do know that float epsilon in every legacy
C/C++ compiler etc I have ever used is defined as about 1e-7 and this is the
value using the formula for fEps above. When I started doing comps using
doubles instead of floats I started using the formula for dEps above which
looks to me like the equivalent for double numbers.
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