Has anyone encounter this this stripping artifact during "RayTracing in one Weekend"?

I am trying to port the "RayTracing in One Weekend" into metal compute shader. I encounter this strip artifacts in my project:

Is it because my random generator does not work well?

Does anyone have a clue?

// 参照 https://www.pcg-random.org/ 实现
typedef struct { uint64_t state;  uint64_t inc; } pcg32_random_t;

uint32_t pcg32_random_r(thread pcg32_random_t* rng)
{
    uint64_t oldstate = rng->state;
    rng->state = oldstate * 6364136223846793005ULL + rng->inc;
    uint32_t xorshifted = ((oldstate >> 18u) ^ oldstate) >> 27u;
    uint32_t rot = oldstate >> 59u;
    return (xorshifted >> rot) | (xorshifted << ((-rot) & 31));
}

void pcg32_srandom_r(thread pcg32_random_t* rng, uint64_t initstate, uint64_t initseq)
{
    rng->state = 0U;
    rng->inc = (initseq << 1u) | 1u;
    pcg32_random_r(rng);
    rng->state += initstate;
    pcg32_random_r(rng);
}

// 生成0～1之间的浮点数
float randomF(thread pcg32_random_t* rng)
{
    //return pcg32_random_r(rng)/float(UINT_MAX);
    return ldexp(float(pcg32_random_r(rng)), -32);
}

// 生成x_min ~ x_max之间的浮点数
float randomRange(thread pcg32_random_t* rng, float x_min, float x_max){
    return randomF(rng) * (x_max - x_min) + x_min;
}