运行基本的Avx512代码时获取非法指令 [英] Getting Illegal Instruction while running a basic Avx512 code

问题描述

我正在尝试学习AVX指令，并且在运行我收到的基本代码时

非法指令(核心已转储)

下面提到了代码，我正在使用

对其进行编译

g ++ -mavx512f 1.cpp

究竟是什么问题，以及如何解决? 谢谢！

#include <immintrin.h>
#include<iostream>
using namespace std;

void add(const float a[], const float b[], float res[], int n)
{
    int i = 0;

    for(; i < (n&(~0x31)) ; i+=32 )
    {
        __m512 x = _mm512_loadu_ps( &a[i] );
        __m512 y = _mm512_loadu_ps( &b[i] );

        __m512 z = _mm512_add_ps(x,y);
        _mm512_stream_ps(&res[i],z);
    }

    for(; i<n; i++) res[i] = a[i] + b[i];
}

int main()
{
    int n = 100000;
    float a[n], b[n], res[n];
    for(int i = 0;i < n; i++)
    {
        a[i] = i;
        b[i] = i+10;
    }
    add(a,b,res,n);
    for(int i=0;i<n;i++) cout<<res[i]<<" ";
    cout<<endl;
    return 0;
}

解决方案

可能您的CPU根本不支持AVX512.到目前为止，几乎只有服务器芯片支持它(例如skylake-server，Cascade湖和至强皮皮).也是英特尔放弃的限量发行的 Cannon Lake笔记本电脑芯片； Ice Lake计划成为第一个支持AVX512的客户端CPU.另请参阅Wikipedia的带有AVX-512的CPU 表.

---

使用g++ -O3 -march=native启用CPU支持的所有功能.

如果遇到编译错误(例如未声明的函数_mm512_loadu_ps)，则您的CPU 不不支持AVX512，因此g ++并未启用它，因此immintrin.h不会定义该内在函数./p>

(或者另一个可能的错误是内联"目标选项不允许的内置函数的错误.)

如果要为其他CPU(而不只是要编译的计算机)制作二进制文件，请仅使用单独的-mavx512f和-mtune=选项.

---

相关:如何测试AVX-512没有支持的硬件的说明?

• 在硬件不足的情况下编码
• 英特尔AVX内部函数:是否有兼容的库?(模拟在编译时而不是在运行时).

I am trying to learn AVX instructions and while running a basic code I recieve

Illegal instruction (core dumped)

The code is mentioned below and I am compiling it using

g++ -mavx512f 1.cpp

What exactly is the problem and how to overcome it? Thank You!

#include <immintrin.h>
#include<iostream>
using namespace std;

void add(const float a[], const float b[], float res[], int n)
{
    int i = 0;

    for(; i < (n&(~0x31)) ; i+=32 )
    {
        __m512 x = _mm512_loadu_ps( &a[i] );
        __m512 y = _mm512_loadu_ps( &b[i] );

        __m512 z = _mm512_add_ps(x,y);
        _mm512_stream_ps(&res[i],z);
    }

    for(; i<n; i++) res[i] = a[i] + b[i];
}

int main()
{
    int n = 100000;
    float a[n], b[n], res[n];
    for(int i = 0;i < n; i++)
    {
        a[i] = i;
        b[i] = i+10;
    }
    add(a,b,res,n);
    for(int i=0;i<n;i++) cout<<res[i]<<" ";
    cout<<endl;
    return 0;
}

解决方案

Probably your CPU doesn't support AVX512 at all. Mostly only server chips so far support it (like skylake-server, Cascade Lake, and Xeon Phi). Also the very-limited-release Cannon Lake laptop chip that Intel is abandoning; Ice Lake is planned to be the first client CPU that supports AVX512. See also Wikipedia's CPUs with AVX-512 table.

---

Use g++ -O3 -march=native to enable everything your CPU supports.

If you get compile errors (like undeclared function _mm512_loadu_ps), your CPU does not support AVX512 so g++ didn't enable it, so immintrin.h wouldn't define that intrinsic.

(Or another possible error is error "inlining" a builtin that target options don't allow.)

Only use separate -mavx512f and -mtune= options if you want to make a binary for other CPUs, not just the machine you're compiling on.

---

Related: How to test AVX-512 instructions w/o supported hardware?

• Coding on insufficient hardware
• Intel AVX intrinsics: any compatibility library out? (emulate at compile time instead of runtime).

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