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https://github.com/ClickHouse/ClickHouse.git
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66 lines
1.7 KiB
C++
66 lines
1.7 KiB
C++
#include <iostream>
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#include <iomanip>
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#if __SSE2__
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#include <emmintrin.h>
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#endif
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#include <common/Types.h>
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#include <IO/ReadHelpers.h>
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#include <IO/ReadBufferFromFileDescriptor.h>
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/** Counts number of 0 in a file.
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* Outputs "fullness" of file - ration of non-0 bytes to the expected number of non-0 bytes in file with random bytes.
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*/
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int main(int argc, char ** argv)
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{
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#if __SSE2__
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try
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{
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DB::ReadBufferFromFileDescriptor in(STDIN_FILENO);
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size_t zeros = 0;
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UInt64 limit = 0;
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if (argc == 2)
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limit = DB::parse<UInt64>(argv[1]);
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while (!in.eof())
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{
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const __m128i zero = {0};
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for (; in.position() + 15 < in.buffer().end(); in.position() += 16)
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{
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__m128i bytes = *reinterpret_cast<const __m128i *>(in.position());
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__m128i byte_mask = _mm_cmpeq_epi8(bytes, zero);
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UInt16 bit_mask = _mm_movemask_epi8(byte_mask);
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zeros += __builtin_popcount(bit_mask);
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}
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for (; in.position() < in.buffer().end(); ++in.position())
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if (*in.position() == 0)
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++zeros;
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if (limit && in.count() >= limit)
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break;
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}
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std::cout << std::fixed
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<< 1 - std::max(0.0, static_cast<double>(zeros) / in.count() - 1.0 / 256)
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<< std::endl;
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}
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catch (const DB::Exception & e)
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{
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std::cerr << e.what() << ", " << e.message() << std::endl
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<< std::endl
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<< "Stack trace:" << std::endl
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<< e.getStackTraceString()
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<< std::endl;
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throw;
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}
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#else
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std::cerr << "Only for x86_64 arch " << std::endl;
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#endif
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return 0;
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}
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