1 | #include <type_traits> |
2 | #include <ext/bit_cast.h> |
3 | #include <Functions/FunctionFactory.h> |
4 | #include <Functions/FunctionUnaryArithmetic.h> |
5 | |
6 | namespace DB |
7 | { |
8 | |
9 | template <typename T> |
10 | inline std::enable_if_t<is_integral_v<T> && (sizeof(T) <= sizeof(UInt32)), T> |
11 | roundDownToPowerOfTwo(T x) |
12 | { |
13 | return x <= 0 ? 0 : (T(1) << (31 - __builtin_clz(x))); |
14 | } |
15 | |
16 | template <typename T> |
17 | inline std::enable_if_t<is_integral_v<T> && (sizeof(T) == sizeof(UInt64)), T> |
18 | roundDownToPowerOfTwo(T x) |
19 | { |
20 | return x <= 0 ? 0 : (T(1) << (63 - __builtin_clzll(x))); |
21 | } |
22 | |
23 | template <typename T> |
24 | inline std::enable_if_t<std::is_same_v<T, Float32>, T> |
25 | roundDownToPowerOfTwo(T x) |
26 | { |
27 | return ext::bit_cast<T>(ext::bit_cast<UInt32>(x) & ~((1ULL << 23) - 1)); |
28 | } |
29 | |
30 | template <typename T> |
31 | inline std::enable_if_t<std::is_same_v<T, Float64>, T> |
32 | roundDownToPowerOfTwo(T x) |
33 | { |
34 | return ext::bit_cast<T>(ext::bit_cast<UInt64>(x) & ~((1ULL << 52) - 1)); |
35 | } |
36 | |
37 | /** For integer data types: |
38 | * - if number is greater than zero, round it down to nearest power of two (example: roundToExp2(100) = 64, roundToExp2(64) = 64); |
39 | * - otherwise, return 0. |
40 | * |
41 | * For floating point data types: zero out mantissa, but leave exponent. |
42 | * - if number is greater than zero, round it down to nearest power of two (example: roundToExp2(3) = 2); |
43 | * - negative powers are also used (example: roundToExp2(0.7) = 0.5); |
44 | * - if number is zero, return zero; |
45 | * - if number is less than zero, the result is symmetrical: roundToExp2(x) = -roundToExp2(-x). (example: roundToExp2(-0.3) = -0.25); |
46 | */ |
47 | |
48 | template <typename T> |
49 | struct RoundToExp2Impl |
50 | { |
51 | using ResultType = T; |
52 | |
53 | static inline T apply(T x) |
54 | { |
55 | return roundDownToPowerOfTwo<T>(x); |
56 | } |
57 | |
58 | #if USE_EMBEDDED_COMPILER |
59 | static constexpr bool compilable = false; |
60 | #endif |
61 | }; |
62 | |
63 | struct NameRoundToExp2 { static constexpr auto name = "roundToExp2" ; }; |
64 | using FunctionRoundToExp2 = FunctionUnaryArithmetic<RoundToExp2Impl, NameRoundToExp2, false>; |
65 | |
66 | template <> struct FunctionUnaryArithmeticMonotonicity<NameRoundToExp2> : PositiveMonotonicity {}; |
67 | |
68 | void registerFunctionRoundToExp2(FunctionFactory & factory) |
69 | { |
70 | factory.registerFunction<FunctionRoundToExp2>(); |
71 | } |
72 | |
73 | } |
74 | |