46 lines
1.1 KiB
C++
46 lines
1.1 KiB
C++
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#include <cctype>
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#include <limits>
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extern "C" {
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#include "lmp_f2c.h"
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// undefine conflicting f2c macros
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#undef min
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#undef max
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doublereal dlamch_(const char *cmach)
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{
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if (!cmach) return 0.0;
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char select = toupper(*cmach);
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// BLAS assumes rounding not truncation => epsilon is half
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const double eps = 0.5 * std::numeric_limits<double>::epsilon();
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if (select == 'E') return eps;
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double min = std::numeric_limits<double>::min();
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const double max = std::numeric_limits<double>::max();
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double small = 1.0 / max;
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if (small >= min) min = small * (1.0 + eps);
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if (select == 'S') return min;
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const double radix = std::numeric_limits<double>::radix;
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if (select == 'B') return radix;
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if (select == 'P') return eps * radix;
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if (select == 'N') return std::numeric_limits<double>::digits;
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if (select == 'M') return std::numeric_limits<double>::min_exponent;
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if (select == 'U') return min;
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if (select == 'L') return std::numeric_limits<double>::max_exponent;
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if (select == 'O') return max;
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return 0.0;
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}
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}
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