C++ 循环未矢量化：未标识循环控制变量

遗憾的是，“英特尔编译器”无法矢量化以下i和j循环：

#pragma ivdep
#pragma vector always
for (  i = 1 ; i < N ; i++ ){ // <- not vectorized
    for (  j = 0 ; j < i ; j++ ){ // <- not vectorized
        // Matrix multiplication on C = x(i) * x(j)
        cblas_dgemm(...,&x[i*BLOCKSIZE*D],... , &x[j*BLOCKSIZE*D],..., c);
        int accum=0;

        // following loop gets vectorized well
        #pragma omp parallel for reduction(+:accum) collapse(2)
        for ( int k = 0 ; k < BLOCKSIZE ; k++ ){
            for ( int l =0 ; l < BLOCKSIZE ; l++ ){                    
                    accum +=  C[k * NRC + l] + p[j*BLOCKSIZE + l] + p[i*BLOCKSIZE+k];
            }
        }

        total += accum;
    }
}

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我真的很困惑，因为我认为控制变量

I

和

j

很明显，我认为我有OpenMP规范中的cannonical循环形式。顺便说一下，

k

-和

l

-循环工作正常。猜猜看？

什么是

N

？它是编译时常量吗？你能给我们看一下定义和初始化吗？不，编译时不知道。我通过命令行选项传递它。什么是

N

？它是编译时常量吗？你能给我们看一下定义和初始化吗？不，编译时不知道。我通过命令行选项传递它。

LOOP BEGIN at i-th loop:
   remark #15521: loop was not vectorized: loop control variable was not identified. Explicitly compute the iteration count before executing the loop or try using canonical loop form from OpenMP specification

   LOOP BEGIN at j-th loop:
      remark #15521: loop was not vectorized: loop control variable was not identified. Explicitly compute the iteration count before executing the loop or try using canonical loop form from OpenMP specification
   LOOP END
LOOP END