基于 SSE reduction of float vector我试图对 unsigned long long 数组求和,但不幸的是没有成功。
uint64_t vsum_uint64 (uint64_t *a, int n)
{
uint64_t sum; // lets say sum fits
__m128 vsum = _mm_set1_ps(0);
for (int i = 0; i < n; i += 2) { // 2 unit64 in single __m128
__m128 v = _mm_loadl_epi64(&a[i]);
vsum = _mm_add_epi64(vsum, v);
}
_mm_store_ss(&sum, vsum);
uint64_t *p = &vsum;
sum+=*(p+1);
// vsum = _mm_hadd_ps(vsum, vsum);
// vsum = _mm_hadd_ps(vsum, vsum);
return sum;
}
这个应该是很对的,但是gcc还是编译不出来。我搜索了答案,但没有找到任何答案。
这是 gcc 所说的:
main.cpp: In function ‘uint64_t vsum_uint64(const uint64_t*, int)’:
main.cpp:73:35: error: cannot convert ‘const uint64_t* {aka const long unsigned int*}’ to ‘const __m128i* {aka const __vector(2) long long int*}’ for argument ‘1’ to ‘__m128i _mm_loadl_epi64(const __m128i*)’
main.cpp:74:31: error: cannot convert ‘__m128 {aka __vector(4) float}’ to ‘__m128i {aka __vector(2) long long int}’ for argument ‘1’ to ‘__m128i _mm_add_epi64(__m128i, __m128i)’
main.cpp:77:25: error: cannot convert ‘uint64_t* {aka long unsigned int*}’ to ‘float*’ for argument ‘1’ to ‘void _mm_store_ss(float*, __m128)’
main.cpp:78:17: error: cannot convert ‘__m128* {aka __vector(4) float*}’ to ‘uint64_t* {aka long unsigned int*}’ in initialization
你能帮我吗?我真的很感激
谢谢
最佳答案
这里有一些事情:
使用
__m128i
而不是__m128
您可以使用
__m128i vsum = _mm_setzero_si128()
对vsum
进行零初始化;对于数据加载,转换为正确的 __m128i 类型并使用打包加载版本(_mm_loadl_epi64 仅加载一个 64 位整数)。所以,要么
for (int i = 0; i < n; i += 2) { // 2 uint64 in single __m128i __m128i v = _mm_loadu_si128(reinterpret_cast<__m128i*>(&a[i]));
或
__m128i* pa = reinterpret_cast<__m128i*>(a); for (int i = 0; i < n; i += 2) { // 2 uint64 in single __m128i __m128i v = _mm_loadu_si128(pa); pa++;
最后,如果为它定义了一个 union (下面是windows/Visual-Studio,但您使用的是不同的环境)。
关于c++ - unsigned long long 数组的 sse 总和,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/22440536/