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我将 Brisk 函数（用于调整图像大小）从 SSE 内在函数转换为 ARM NEON 内在函数，以便在 ARM 架构上执行它。如果支持，Brisk 使用 SSE 函数，否则使用 opencv 函数。SSE 当然更快。我逐步转换了 ARM neon 中的 SSE 函数，但是当我测量与 openCV resize 函数相比的执行时间时，结果是我的函数更慢（0.2ms vs 0.4ms）。这是代码：

上交所：

inline void BriskLayer::halfsample(const cv::Mat& srcimg, cv::Mat& dstimg){
const unsigned short leftoverCols = ((srcimg.cols%16)/2);// take care with border...
const bool noleftover = (srcimg.cols%16)==0; // note: leftoverCols can be zero butthis still false...

// make sure the destination image is of the right size:
assert(srcimg.cols/2==dstimg.cols);
assert(srcimg.rows/2==dstimg.rows);

// mask needed later:
register __m128i mask = _mm_set_epi32 (0x00FF00FF, 0x00FF00FF, 0x00FF00FF, 0x00FF00FF);
// to be added in order to make successive averaging correct:
register __m128i ones = _mm_set_epi32 (0x11111111, 0x11111111, 0x11111111, 0x11111111);

// data pointers:
__m128i* p1=(__m128i*)srcimg.data;
__m128i* p2=(__m128i*)(srcimg.data+srcimg.cols);
__m128i* p_dest=(__m128i*)dstimg.data;
unsigned char* p_dest_char;//=(unsigned char*)p_dest;

// size:
const unsigned int size = (srcimg.cols*srcimg.rows)/16;
const unsigned int hsize = srcimg.cols/16;
__m128i* p_end=p1+size;
unsigned int row=0;
const unsigned int end=hsize/2;
bool half_end;
if(hsize%2==0)
    half_end=false;
else
    half_end=true;
while(p2<p_end){
    for(unsigned int i=0; i<end;i++){
        // load the two blocks of memory:
        __m128i upper;
        __m128i lower;
        if(noleftover){
            upper=_mm_load_si128(p1);
            lower=_mm_load_si128(p2);
        }
        else{
            upper=_mm_loadu_si128(p1);
            lower=_mm_loadu_si128(p2);
        }

        __m128i result1=_mm_adds_epu8 (upper, ones);
        result1=_mm_avg_epu8 (upper, lower);

        // increment the pointers:
        p1++;
        p2++;

        // load the two blocks of memory:
        upper=_mm_loadu_si128(p1);
        lower=_mm_loadu_si128(p2);
        __m128i result2=_mm_adds_epu8 (upper, ones);
        result2=_mm_avg_epu8 (upper, lower);
        // calculate the shifted versions:
        __m128i result1_shifted = _mm_srli_si128 (result1, 1);
        __m128i result2_shifted = _mm_srli_si128 (result2, 1);
        // pack:
        __m128i result=_mm_packus_epi16 (_mm_and_si128 (result1, mask),
                _mm_and_si128 (result2, mask));
        __m128i result_shifted = _mm_packus_epi16 (_mm_and_si128 (result1_shifted, mask),
                _mm_and_si128 (result2_shifted, mask));
        // average for the second time:
        result=_mm_avg_epu8(result,result_shifted);

        // store to memory
        _mm_storeu_si128 (p_dest, result);

        // increment the pointers:
        p1++;
        p2++;
        p_dest++;
        //p_dest_char=(unsigned char*)p_dest;
    }
    // if we are not at the end of the row, do the rest:
    if(half_end){
        // load the two blocks of memory:
        __m128i upper;
        __m128i lower;
        if(noleftover){
            upper=_mm_load_si128(p1);
            lower=_mm_load_si128(p2);
        }
        else{
            upper=_mm_loadu_si128(p1);
            lower=_mm_loadu_si128(p2);
        }

        __m128i result1=_mm_adds_epu8 (upper, ones);
        result1=_mm_avg_epu8 (upper, lower);

        // increment the pointers:
        p1++;
        p2++;

        // compute horizontal pairwise average and store
        p_dest_char=(unsigned char*)p_dest;
        const UCHAR_ALIAS* result=(UCHAR_ALIAS*)&result1;
        for(unsigned int j=0; j<8; j++){
            *(p_dest_char++)=(*(result+2*j)+*(result+2*j+1))/2;
        }
        //p_dest_char=(unsigned char*)p_dest;
    }
    else{
        p_dest_char=(unsigned char*)p_dest;
    }

    if(noleftover){
        row++;
        p_dest=(__m128i*)(dstimg.data+row*dstimg.cols);
        p1=(__m128i*)(srcimg.data+2*row*srcimg.cols);
        //p2=(__m128i*)(srcimg.data+(2*row+1)*srcimg.cols);
        //p1+=hsize;
        p2=p1+hsize;
    }
    else{
        const unsigned char* p1_src_char=(unsigned char*)(p1);
        const unsigned char* p2_src_char=(unsigned char*)(p2);
        for(unsigned int k=0; k<leftoverCols; k++){
            unsigned short tmp = p1_src_char[k]+p1_src_char[k+1]+
                    p2_src_char[k]+p2_src_char[k+1];
            *(p_dest_char++)=(unsigned char)(tmp/4);
        }
        // done with the two rows:
        row++;
        p_dest=(__m128i*)(dstimg.data+row*dstimg.cols);
        p1=(__m128i*)(srcimg.data+2*row*srcimg.cols);
        p2=(__m128i*)(srcimg.data+(2*row+1)*srcimg.cols);
    }
}

}

手臂霓虹灯：

void halfsample(const cv::Mat& srcimg, cv::Mat& dstimg){
const unsigned short leftoverCols = ((srcimg.cols%16)/2);// take care with border...
const bool noleftover = (srcimg.cols%16)==0; // note: leftoverCols can be zero but this still false...

// make sure the destination image is of the right size:
//assert(srcimg.cols/2==dstimg.cols);
//assert(srcimg.rows/2==dstimg.rows);
//int32x4_t zero = vdupq_n_s8(0);

// mask needed later:
//register __m128i mask = _mm_set_epi32 (0x00FF00FF, 0x00FF00FF, 0x00FF00FF, 0x00FF00FF);
int32x4_t mask = vdupq_n_s32(0x00FF00FF);
// to be added in order to make successive averaging correct:
int32x4_t ones = vdupq_n_s32(0x11111111);
    print128_numhex(mask);
// data pointers:
int32_t* p1=(int32_t*)srcimg.data;
int32_t* p2=(int32_t*)(srcimg.data+srcimg.cols);
int32_t* p_dest=(int32_t*)dstimg.data;
unsigned char* p_dest_char;//=(unsigned char*)p_dest;
int k=0;
// size:
const unsigned int size = (srcimg.cols*srcimg.rows)/16;
const unsigned int hsize = srcimg.cols/16;
int32_t* p_end=p1+size*4;
unsigned int row=0;
const unsigned int end=hsize/2;
bool half_end;
if(hsize%2==0)
    half_end=false;
else
    half_end=true;
while(p2<p_end){
    k++;
    for(unsigned int i=0; i<end;i++){
        // load the two blocks of memory:
        int32x4_t upper;
        int32x4_t lower;
        if(noleftover){
            upper=vld1q_s32(p1);
            lower=vld1q_s32(p2);
        }
        else{
            upper=vld1q_s32(p1);
            lower=vld1q_s32(p2);
        }

        int32x4_t result1=vaddq_s32(upper, ones);
        result1=vrhaddq_u8(upper, lower);

        // increment the pointers:
        p1=p1+4;
        p2=p2+4;

        // load the two blocks of memory:
        upper=vld1q_s32(p1);
        lower=vld1q_s32(p2);
        int32x4_t result2=vaddq_s32(upper, ones);
        result2=vrhaddq_u8(upper, lower);
        // calculate the shifted versions:
        int32x4_t result1_shifted = vextq_u8(result1,vmovq_n_u8(0),1);
        int32x4_t result2_shifted = vextq_u8(result2,vmovq_n_u8(0),1);
        // pack:
        int32x4_t result= vcombine_u8(vqmovn_u16(vandq_u32(result1, mask)),
                vqmovn_u16(vandq_u32 (result2, mask)));

        int32x4_t result_shifted =  vcombine_u8(vqmovn_u16(vandq_u32 (result1_shifted, mask)),
                vqmovn_u16(vandq_u32(result2_shifted, mask)));
        // average for the second time:
        result=vrhaddq_u8(result,result_shifted);

        // store to memory
        vst1q_s32(p_dest, result);

        // increment the pointers:
        p1=p1+4;
        p2=p2+4;
        p_dest=p_dest+4;
        //p_dest_char=(unsigned char*)p_dest;
    }
    // if we are not at the end of the row, do the rest:
    if(half_end){
        std::cout<<"entra in half_end" << std::endl;
        // load the two blocks of memory:
        int32x4_t upper;
        int32x4_t lower;
        if(noleftover){
            upper=vld1q_s32(p1);
            lower=vld1q_s32(p2);
        }
        else{
            upper=vld1q_s32(p1);
            lower=vld1q_s32(p2);
        }

        int32x4_t result1=vqaddq_s32(upper, ones);
        result1=vrhaddq_u8(upper, lower);

        // increment the pointers:
        p1=p1+4;
        p2=p2+4;

        // compute horizontal pairwise average and store
        p_dest_char=(unsigned char*)p_dest;
        const UCHAR_ALIAS* result=(UCHAR_ALIAS*)&result1;
        for(unsigned int j=0; j<8; j++){
            *(p_dest_char++)=(*(result+2*j)+*(result+2*j+1))/2;
        }
        //p_dest_char=(unsigned char*)p_dest;
    }
    else{
        p_dest_char=(unsigned char*)p_dest;
    }

    if(noleftover){
        row++;
        p_dest=(int32_t*)(dstimg.data+row*dstimg.cols);
        p1=(int32_t*)(srcimg.data+2*row*srcimg.cols);
        //p2=(__m128i*)(srcimg.data+(2*row+1)*srcimg.cols);
        //p1+=hsize;
        p2=p1+hsize*4;
    }
    else{
        const unsigned char* p1_src_char=(unsigned char*)(p1);
        const unsigned char* p2_src_char=(unsigned char*)(p2);
        for(unsigned int k=0; k<leftoverCols; k++){
            unsigned short tmp = p1_src_char[k]+p1_src_char[k+1]+
                    p2_src_char[k]+p2_src_char[k+1];
            *(p_dest_char++)=(unsigned char)(tmp/4);
        }
        // done with the two rows:
        row++;
        p_dest=(int32_t*)(dstimg.data+row*dstimg.cols);
        p1=(int32_t*)(srcimg.data+2*row*srcimg.cols);
        p2=(int32_t*)(srcimg.data+(2*row+1)*srcimg.cols);
    }
}

}

ARM 和 SSE 函数的输出完全相同。问题是执行时间。

4

1 回答 1

0

您应该知道，内在函数和内联汇编代码都不能像本机汇编中的手写代码那样“完美无缺”。

更糟糕的是，有时编译器——尤其是像 GCC 这样的开源编译器——会放置一些不必要的指令，这些指令会导致流水线停顿，这会花费超过十个周期。当这发生在最里面的循环中时，这对性能来说是直接致命的。

为什么不发布代码的反汇编？有内在问题的人应该总是先看看它。（并尽快停止使用内在函数）

于 2013-09-10T02:03:03.663 回答