blob: 8eb064f4a323d98b3517849a1100ffb246470bd9 (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
|
#include <Common/randomSeed.h>
#include <Functions/FunctionFactory.h>
#include <Functions/FunctionsRandom.h>
#include <pcg-random/pcg_random.hpp>
namespace DB
{
namespace
{
struct CanonicalRandImpl
{
static void execute(char * output, size_t size)
{
pcg64_fast rng1(randomSeed());
pcg64_fast rng2(randomSeed());
std::uniform_real_distribution<Float64> distribution1(min, max);
std::uniform_real_distribution<Float64> distribution2(min, max);
for (const char * end = output + size; output < end; output += 16)
{
unalignedStore<Float64>(output, distribution1(rng1));
unalignedStore<Float64>(output + 8, distribution2(rng2));
}
}
/// It is guaranteed (by PaddedPODArray) that we can overwrite up to 15 bytes after end.
private:
const static constexpr Float64 min = 0;
const static constexpr Float64 max = 1;
};
struct NameCanonicalRand
{
static constexpr auto name = "randCanonical";
};
class FunctionCanonicalRand : public FunctionRandomImpl<CanonicalRandImpl, Float64, NameCanonicalRand>
{
public:
static FunctionPtr create(ContextPtr /*context*/) { return std::make_shared<FunctionCanonicalRand>(); }
};
}
REGISTER_FUNCTION(CanonicalRand)
{
factory.registerFunction<FunctionCanonicalRand>(FunctionDocumentation{
.description=R"(
The function generates pseudo random results with independent and identically distributed uniformly distributed values in [0, 1).
Non-deterministic. Return type is Float64.
)",
.examples{{"randCanonical", "SELECT randCanonical()", ""}},
.categories{"Mathematical"}});
}
}
|
