MiniVec.h

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// The MIT License (MIT)
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#pragma once

#include <cmath>

#ifdef __CUDACC__
#define FN_SPECIFIERS inline __host__ __device__
#else
#define FN_SPECIFIERS inline
#endif

namespace open3d {
namespace utility {

template <class T, int N>
struct MiniVec {
    typedef T Scalar_t;

    FN_SPECIFIERS MiniVec() {}

    template <class... TInit>
    FN_SPECIFIERS explicit MiniVec(TInit... as) : arr{as...} {}

    FN_SPECIFIERS explicit MiniVec(const T* const ptr) {
        for (int i = 0; i < N; ++i) operator[](i) = ptr[i];
    }

    FN_SPECIFIERS const T operator[](size_t i) const { return arr[i]; }
    FN_SPECIFIERS T& operator[](size_t i) { return arr[i]; }
    template <class T2>
    FN_SPECIFIERS MiniVec<T2, N> cast() const {
        MiniVec<T2, N> a;
        for (int i = 0; i < N; ++i) a[i] = T2(operator[](i));
        return a;
    }

    FN_SPECIFIERS T dot(const MiniVec<T, N>& a) const {
        T result = 0;
        for (int i = 0; i < N; ++i) result += operator[](i) * a[i];
        return result;
    }

    FN_SPECIFIERS MiniVec<T, N> abs() const {
        MiniVec<float, N> r;
        for (int i = 0; i < N; ++i) r[i] = std::abs(operator[](i));
        return r;
    }

    T arr[N];
};

template <int N>
FN_SPECIFIERS MiniVec<float, N> floor(const MiniVec<float, N>& a) {
    MiniVec<float, N> r;
    for (int i = 0; i < N; ++i) r[i] = floorf(a[i]);
    return r;
}

template <int N>
FN_SPECIFIERS MiniVec<double, N> floor(const MiniVec<double, N>& a) {
    MiniVec<double, N> r;
    for (int i = 0; i < N; ++i) r[i] = std::floor(a[i]);
    return r;
}

template <class T, int N>
FN_SPECIFIERS bool operator==(const MiniVec<T, N>& a, const MiniVec<T, N>& b) {
    bool result = true;
    for (int i = 0; i < N && result; ++i) result = result && a[i] == b[i];
    return result;
}

template <class T, int N>
FN_SPECIFIERS bool operator!=(const MiniVec<T, N>& a, const MiniVec<T, N>& b) {
    return !(a == b);
}

template <class T, int N>
FN_SPECIFIERS MiniVec<T, N> operator-(const MiniVec<T, N>& a) {
    MiniVec<T, N> r;
    for (int i = 0; i < N; ++i) r[i] = -a[i];
    return r;
}

#define DEFINE_OPERATOR(op, opas)                                          \
    template <class T, int N>                                              \
    FN_SPECIFIERS MiniVec<T, N> operator op(const MiniVec<T, N>& a,        \
                                            const MiniVec<T, N>& b) {      \
        MiniVec<T, N> c;                                                   \
        for (int i = 0; i < N; ++i) c[i] = a[i] op b[i];                   \
        return c;                                                          \
    }                                                                      \
                                                                           \
    template <class T, int N>                                              \
    FN_SPECIFIERS void operator opas(MiniVec<T, N>& a,                     \
                                     const MiniVec<T, N>& b) {             \
        for (int i = 0; i < N; ++i) a[i] opas b[i];                        \
    }                                                                      \
                                                                           \
    template <class T, int N>                                              \
    FN_SPECIFIERS MiniVec<T, N> operator op(const MiniVec<T, N>& a, T b) { \
        MiniVec<T, N> c;                                                   \
        for (int i = 0; i < N; ++i) c[i] = a[i] op b;                      \
        return c;                                                          \
    }                                                                      \
                                                                           \
    template <class T, int N>                                              \
    FN_SPECIFIERS MiniVec<T, N> operator op(T a, const MiniVec<T, N>& b) { \
        MiniVec<T, N> c;                                                   \
        for (int i = 0; i < N; ++i) c[i] = a op b[i];                      \
        return c;                                                          \
    }                                                                      \
                                                                           \
    template <class T, int N>                                              \
    FN_SPECIFIERS void operator opas(MiniVec<T, N>& a, T b) {              \
        for (int i = 0; i < N; ++i) a[i] opas b;                           \
    }

DEFINE_OPERATOR(+, +=)
DEFINE_OPERATOR(-, -=)
DEFINE_OPERATOR(*, *=)
DEFINE_OPERATOR(/, /=)
#undef DEFINE_OPERATOR
#undef FN_SPECIFIERS

}  // namespace utility
}  // namespace open3d