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Diffstat (limited to 'indra/llmath/llmath.h')
| -rw-r--r-- | indra/llmath/llmath.h | 24 |
1 files changed, 24 insertions, 0 deletions
diff --git a/indra/llmath/llmath.h b/indra/llmath/llmath.h index 0372bae106..916f4aa6c7 100644 --- a/indra/llmath/llmath.h +++ b/indra/llmath/llmath.h @@ -103,6 +103,30 @@ const F32 FP_MAG_THRESHOLD = 0.0000001f; // TODO: Replace with logic like is_approx_equal inline BOOL is_approx_zero( F32 f ) { return (-F_APPROXIMATELY_ZERO < f) && (f < F_APPROXIMATELY_ZERO); } +// These functions work by interpreting sign+exp+mantissa as an unsigned +// integer. +// For example: +// x = <sign>1 <exponent>00000010 <mantissa>00000000000000000000000 +// y = <sign>1 <exponent>00000001 <mantissa>11111111111111111111111 +// +// interpreted as ints = +// x = 10000001000000000000000000000000 +// y = 10000000111111111111111111111111 +// which is clearly a different of 1 in the least significant bit +// Values with the same exponent can be trivially shown to work. +// +// WARNING: Denormals of opposite sign do not work +// x = <sign>1 <exponent>00000000 <mantissa>00000000000000000000001 +// y = <sign>0 <exponent>00000000 <mantissa>00000000000000000000001 +// Although these values differ by 2 in the LSB, the sign bit makes +// the int comparison fail. +// +// WARNING: NaNs can compare equal +// There is no special treatment of exceptional values like NaNs +// +// WARNING: Infinity is comparable with F32_MAX and negative +// infinity is comparable with F32_MIN + inline BOOL is_approx_equal(F32 x, F32 y) { const S32 COMPARE_MANTISSA_UP_TO_BIT = 0x02; |