neon和sve实现spmv的代码

由于无法确定您的具体需求和背景，我提供两种实现方式，一种是使用NEON指令集，另一种是使用SVE指令集。

使用NEON指令集实现SPMV：

#include <arm_neon.h>

void spmv_neon(float* val, int* col_idx, int* row_ptr, float* x, float* y, int m)
{
    for (int i = 0; i < m; i++)
    {
        float32x4_t sum = vdupq_n_f32(0.0f);
        for (int j = row_ptr[i]; j < row_ptr[i + 1]; j += 4)
        {
            int32x4_t idx = vld1q_s32(&col_idx[j]);
            float32x4_t v = vld1q_f32(&val[j]);
            float32x4_t x_v = vld1q_f32(&x[idx[0]]);
            sum = vmlaq_f32(sum, v, x_v);
        }
        float32x2_t s2 = vpadd_f32(vget_low_f32(sum), vget_high_f32(sum));
        float32x2_t s = vpadd_f32(s2, s2);
        y[i] = s[0];
    }
}

使用SVE指令集实现SPMV：

#include <arm_sve.h>

void spmv_sve(float* val, int* col_idx, int* row_ptr, float* x, float* y, int m)
{
    for (int i = 0; i < m; i++)
    {
        svfloat32_t sum = svdup_f32(0.0f);
        for (int j = row_ptr[i]; j < row_ptr[i + 1]; j += svcntw())
        {
            svbool_t p = svwhilelt_b32(j, row_ptr[i + 1]);
            int32_t idx[svcntw()];
            float32_t v[svcntw()];
            svld1_gather_u32base_s32(&idx[0], p, &col_idx[j]);
            svld1_gather_u32base_f32(&v[0], p, &val[j]);
            svfloat32_t x_v = svld1_gather_index_f32(p, x, &idx[0]);
            sum = svmla_f32_x(p, sum, x_v, svld1(p, &v[0]));
        }
        float32_t s = svaddv_f32(svptrue_b32(), sum);
        y[i] = s;
    }
}

需要注意的是，SVE指令集需要ARMv8.2-A架构及以上，且需要编译器和操作系统的支持。