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A definition of the arithmetic constants

The supplied functions SMACHR and DMACHR return values for various machine dependent constants, for single and double precision arithmetic, respectively. These machine constants are denoted R$n$ in single precision and D$n$ in double precision. We recapitulate them in the following table

Parameter Brief description
R1, D1 the smallest positive number $\varepsilon_1$ such that $1 + \varepsilon_1 > 1$
R2, D2 the smallest positive number $\varepsilon_2$ such that $1 - \varepsilon_2 < 1$
R3, D3 the smallest nonzero positive number
R4, D4 the smallest full precision positive number;
R5, D5 the largest finite positive number

Each of these numbers should be modified, in all.cf and/or <your_system>.cf, found under $MYSIFDEC/config.



Dominique Orban 2004-09-16