如何在现代 x86-64 Intel CPU 上实现每周期 4 次 FLOP？

如何实现每周期理论最大4次FLOP？

理论上可以实现4个浮点的峰值性能现代 x86-64 Intel CPU 上每个周期的运算（双精度），通过利用以下内容技巧：

优化 SSE 指令代码

• 使用 SSE（流 SIMD 扩展）指令，可以并行处理多个数据元素。
• 确保代码正确对齐以实现最佳 SSE性能。

循环展开和交错

• 展开内部循环以提高指令级并行性。
• 交错乘法和加法利用CPU的流水线技术

将操作分成三组

• 将操作按三组排列，以匹配某些 Intel CPU 上的执行单元。这允许在 add 和 mul 指令之间交替，从而最大化吞吐量。

避免不必要的停顿和依赖

• 最小化指令之间的数据依赖性以避免停顿.
• 使用编译器优化（-O3 或更高版本）来帮助识别和消除不必要的

示例代码

以下代码片段演示了如何在 Intel Core i5 和 Core i7 CPU 上实现接近峰值性能：

#include <emmintrin.h>
#include <omp.h>
#include <iostream>
using namespace std;

typedef unsigned long long uint64;

double test_dp_mac_SSE(double x, double y, uint64 iterations) {
    register __m128d r0, r1, r2, r3, r4, r5, r6, r7, r8, r9, rA, rB, rC, rD, rE, rF;

    // Generate starting data.
    r0 = _mm_set1_pd(x);
    r1 = _mm_set1_pd(y);

    r8 = _mm_set1_pd(-0.0);

    r2 = _mm_xor_pd(r0, r8);
    r3 = _mm_or_pd(r0, r8);
    r4 = _mm_andnot_pd(r8, r0);
    r5 = _mm_mul_pd(r1, _mm_set1_pd(0.37796447300922722721));
    r6 = _mm_mul_pd(r1, _mm_set1_pd(0.24253562503633297352));
    r7 = _mm_mul_pd(r1, _mm_set1_pd(4.1231056256176605498));
    r8 = _mm_add_pd(r0, _mm_set1_pd(0.37796447300922722721));
    r9 = _mm_add_pd(r1, _mm_set1_pd(0.24253562503633297352));
    rA = _mm_sub_pd(r0, _mm_set1_pd(4.1231056256176605498));
    rB = _mm_sub_pd(r1, _mm_set1_pd(4.1231056256176605498));

    rC = _mm_set1_pd(1.4142135623730950488);
    rD = _mm_set1_pd(1.7320508075688772935);
    rE = _mm_set1_pd(0.57735026918962576451);
    rF = _mm_set1_pd(0.70710678118654752440);

    uint64 iMASK = 0x800fffffffffffffull;
    __m128d MASK = _mm_set1_pd(*(double*)&iMASK);
    __m128d vONE = _mm_set1_pd(1.0);

    uint64 c = 0;
    while (c < iterations) {
        size_t i = 0;
        while (i < 1000) {
            // Main computational loop

            r0 = _mm_mul_pd(r0, rC);
            r1 = _mm_add_pd(r1, rD);
            r2 = _mm_mul_pd(r2, rE);
            r3 = _mm_sub_pd(r3, rF);
            r4 = _mm_mul_pd(r4, rC);
            r5 = _mm_add_pd(r5, rD);
            r6 = _mm_mul_pd(r6, rE);
            r7 = _mm_sub_pd(r7, rF);
            r8 = _mm_mul_pd(r8, rC);
            r9 = _mm_add_pd(r9, rD);
            rA = _mm_mul_pd(rA, rE);
            rB = _mm_sub_pd(rB, rF);

            r0 = _mm_add_pd(r0, rF);
            r1 = _mm_mul_pd(r1, rE);
            r2 = _mm_sub_pd(r2, rD);
            r3 = _mm_mul_pd(r3, rC);
            r4 = _mm_add_pd(r4, rF);
            r5 = _mm_mul_pd(r5, rE);
            r6 = _mm_sub_pd(r6, rD);
            r7 = _mm_mul_pd(r7, rC);
            r8 = _mm_add_pd(r8, rF);
            r9 = _mm_mul_pd(r9, rE);
            rA = _mm_sub_pd(rA, rD);
            rB = _mm_mul_pd(rB, rC);

            r0 = _mm_mul_pd(r0, rC);
            r1 = _mm_add_pd(r1, rD);
            r2 = _mm_mul_pd(r2, rE);
            r3 = _mm_sub_pd(r3, rF);
            r4 = _mm_mul_pd(r4, rC);
            r5 = _mm_add_pd(r5, rD);
            r6 = _mm_mul_pd(r6, rE);
            r7 = _mm_sub_pd(r7, rF);
            r8 = _mm_mul_pd(r8, rC);
            r9 = _mm_add_pd(r9, rD);

以上是如何在现代 x86-64 Intel CPU 上实现每周期 4 次 FLOP？的详细内容。更多信息请关注PHP中文网其他相关文章！