c++多类别nms

    static __device__ float box_iou(
        float aleft, float atop, float aright, float abottom,
        float bleft, float btop, float bright, float bbottom)
    {

        float cleft = max(aleft, bleft);
        float ctop = max(atop, btop);
        float cright = min(aright, bright);
        float cbottom = min(abottom, bbottom);

        float c_area = max(cright - cleft, 0.0f) * max(cbottom - ctop, 0.0f);
        if (c_area == 0.0f)
            return 0.0f;

        float a_area = max(0.0f, aright - aleft) * max(0.0f, abottom - atop);
        float b_area = max(0.0f, bright - bleft) * max(0.0f, bbottom - btop);
        return c_area / (a_area + b_area - c_area);
    }

static __global__ void nms_kernel(float *bboxes, int max_objects, float threshold, ObjectDetectType_e detect_type)
{

    int position = (blockDim.x * blockIdx.x + threadIdx.x);
    int count = min((int)*bboxes, max_objects);
    if (position >= count)
        return;
    // left, top, right, bottom, confidence, class, keepflag
    int COMMON_BOX_ELEMENT;
    if (detect_type == DETECT_FACE ) {
        COMMON_BOX_ELEMENT = FACE_BOX_ELEMENT;
    }else if(detect_type == DETECT_PLATE){
        COMMON_BOX_ELEMENT = PLATE_BOX_ELEMENT;
    }else{
        COMMON_BOX_ELEMENT = NUM_BOX_ELEMENT;
    }

    float *pcurrent = bboxes + 1 + position * COMMON_BOX_ELEMENT;

    for (int i = 0; i < count; ++i)
    {
        float *pitem = bboxes + 1 + i * COMMON_BOX_ELEMENT;
        if (i == position || pcurrent[5] != pitem[5])
            continue;

        if (pitem[4] >= pcurrent[4])
        {
            if (pitem[4] == pcurrent[4] && i < position)
                continue;


            float iou = box_iou(
                pcurrent[0], pcurrent[1], pcurrent[2], pcurrent[3],
                pitem[0], pitem[1], pitem[2], pitem[3]);

            if (iou > threshold)
            {
                pcurrent[6] = 0; // 1=keep, 0=ignore
                return;
            }
        }
    }
}