exp2_fp()

static FASTLED_FORCE_INLINE u8x24 fl::u8x24::exp2_fp ( u8x24 x )

inlinestaticprivate

Definition at line 236 of file u8x24.h.

                                                                   {
        u8x24 fl_val = floor(x);
        u8x24 fr = x - fl_val;
        u32 n = fl_val.mValue >> FRAC_BITS;
 
        // Prevent overflow
        if (n >= INT_BITS) return from_raw(0xFFFFFFFFu);
 
        u32 int_pow = static_cast<u32>(SCALE) << n;
 
        // 4-term minimax coefficients for 2^t - 1, t in [0,1).
        constexpr int IFRAC = 24;
        constexpr u64 d0 = 11629376ULL;  // 0.69316 * 2^24
        constexpr u64 d1 = 4038400ULL;   // 0.24071 * 2^24
        constexpr u64 d2 = 895232ULL;    // 0.05336 * 2^24
        constexpr u64 d3 = 214016ULL;    // 0.01276 * 2^24
 
        u64 fr24 = static_cast<u64>(fr.mValue);
        // Horner: 1 + fr * (d0 + fr * (d1 + fr * (d2 + fr * d3)))
        u64 acc = d3;
        acc = d2 + ((acc * fr24) >> IFRAC);
        acc = d1 + ((acc * fr24) >> IFRAC);
        acc = d0 + ((acc * fr24) >> IFRAC);
        constexpr u64 one24 = 1ULL << IFRAC;
        u64 frac_pow24 = one24 + ((acc * fr24) >> IFRAC);
 
        // Scale by int_pow (result stays at 24 frac bits).
        u64 result = (static_cast<u64>(int_pow) * frac_pow24) >> FRAC_BITS;
        return from_raw(static_cast<u32>(result));
    }

References u8x24(), FASTLED_FORCE_INLINE, FL_NOEXCEPT, floor(), FRAC_BITS, from_raw(), INT_BITS, mValue, SCALE, and fl::x.

Referenced by pow().

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