With the acceleration instruction set sse4.1 ceil () function

ceil C / C ++ Standard Library () function, can accelerate it?

In the OpenCV, we see cvCeil () function, which is sse2 accelerated.

In fact, I use a PC, avx2 have supported, sse, avx series is incremental supported by sse4.1 to optimize it, you should still be able to widespread use.

Most programs written on the nature of most people, are calling ready-made package / API, is nothing more than transfer package Xia also despise chain only.

Today, we make a return to SSE4.1 the transfer package Xia, so that the original calculation of the level of 100ms, optimized to 25ms, than the clang-8.0 (actually it's standard library) in the ceil () and then fast 5ms:

#include <iostream>
#include <cmath>
#include <sstream>
#include <chrono>

//sse2
#if defined _MSC_VER && defined _M_X64 || (defined __GNUC__ && defined __SSE2__&& !defined __APPLE__)
#include <emmintrin.h>
#endif

//sse 4.1
#include <smmintrin.h>


//sse2 optimized
inline int cvCeil(double value)
{
#if defined _MSC_VER && defined _M_X64 || (defined __GNUC__ && defined __SSE2__&& !defined __APPLE__)
    __m128d t = _mm_set_sd( value );
    int i = _mm_cvtsd_si32(t);
    return i + _mm_movemask_pd(_mm_cmplt_sd(_mm_cvtsi32_sd(t,i), t));
#elif defined __GNUC__
    int i = (int)value;
    return i + (i < value);
#else
    int i = cvRound(value);
    float diff = (float)(i - value);
    return i + (diff < 0);
#endif
}


//sse4 optimized
inline int myCeil(double value)
{
#if defined _MSC_VER && defined _M_X64 || (defined __GNUC__ && defined __SSE2__&& !defined __APPLE__)

    __m128d val = _mm_set_sd(value);
    __m128d dst;
    _mm_round_sd(dst, val, _MM_FROUND_CEIL);
    return _mm_cvtsd_si32(dst);


    //__m128d t = _mm_set_sd( value );
    //int i = _mm_cvtsd_si32(t);
    //return i + _mm_movemask_pd(_mm_cmplt_sd(_mm_cvtsi32_sd(t,i), t));
#elif defined __GNUC__
    int i = (int)value;
    return i + (i < value);
#else
    int i = cvRound(value);
    float diff = (float)(i - value);
    return i + (diff < 0);
#endif
}



template<typename T, typename P>
std::string toString(std::chrono::duration<T,P> dt)
{
    std::ostringstream str;
    using namespace std::chrono;
    str << duration_cast<microseconds>(dt).count()*1e-3 << " ms";
    return str.str();
}

int main () {
    volatile double x = 34.234;
    volatile double y1, y2, y3;
    const int MAX_ITER=100000000;
    const auto t0 = std::chrono::steady_clock::now();

    for(int i=0; i<MAX_ITER; i++) {
        y1 = std::ceil(x);
    }
    const auto t1 = std::chrono::steady_clock::now();

    for(int i=0; i<MAX_ITER; i++) {
        y2 = cvCeil(x);
    }
    const auto t2 = std::chrono::steady_clock::now();

    for(int i=0; i<MAX_ITER; i++) {
        y3 = myCeil(x);
    }
    const auto t3 = std::chrono::steady_clock::now();



    std::cout << "std::ceil: " << toString(t1-t0) << "\n";
    std::cout << "cvCeil   : " << toString(t2-t1) << "\n";
    std::cout << "myCeil   : " << toString(t3-t2) << "\n";
    std::cout << "y1=" << y1 << ", y2=" << y2 << ", y3=" << y3 << std::endl;

    return 0;
}

Compiler directive:

clang++-8 main8.cpp -O3 -o a8 -std=c++11 -msse4

Run output:

std::ceil: 30.347 ms
cvCeil   : 106.99 ms
myCeil   : 25.318 ms
y1=35, y2=35, y3=35

refs:
is cvCeil() faster than standard library?
MSDN - _mm_round_sd

With the acceleration instruction set sse4.1 ceil () function

Guess you like