我有以下有效的 for 回圈：
static const int ny = 10;
std::vector<double> ygl(ny 1);
double *dVGL;
dVGL = (double*) fftw_malloc(((ny 1)*(ny 1))*sizeof(double));
memset(dVGL, 42, ((ny 1)*(ny 1))* sizeof(double));
double *dummy1;
dummy1 = (double*) fftw_malloc(((ny 1)*(ny 1))*sizeof(double));
memset(dummy1, 42, ((ny 1)*(ny 1))* sizeof(double));
double *dummy2;
dummy2 = (double*) fftw_malloc(((ny 1)*(ny 1))*sizeof(double));
memset(dummy2, 42, ((ny 1)*(ny 1))* sizeof(double));
for (int i = 0; i < ny 1; i ){
for (int j = 0; j < ny 1; j ){
ygl[j] = -1. * cos(((j) * EIGEN_PI )/ny);
dummy1[j ny*i] = 1./(sqrt(1-pow(ygl[j],2)));
dummy2[j ny*i] = 1. * (i);
dVGL[j ny*i] = dummy1[j ny*i] * sin(acos(ygl[j]) * (i)) * dummy2[j ny*i];
}
}
以上作業正常，現在我轉換為 Eigen，我得到了結果：
Eigen::Matrix< double, 1, ny 1> v1;
v1.setZero();
std::iota(v1.begin(), v1.end(), 0);
Eigen::Matrix< double, ny 1, ny 1> dummy1;
dummy1.setZero();
Eigen::Matrix< double, ny 1, ny 1> dummy2;
dummy2.setZero();
for (int j = 0; j < ny 1; j ){
v[j] = 1./(sqrt(1-pow(ygl[j],2)));
}
dummy1 = v.array().matrix().asDiagonal(); //this is correct
dummy2 = v1.array().matrix().asDiagonal(); //this is correct
Eigen::Matrix< double, ny 1, ny 1> dVGL;
dVGL.setZero();
for (int i = 0; i < ny 1; i ){
for (int j = 0; j < ny 1; j ){
ygl[j] = -1. * cos(((j) * EIGEN_PI )/ny);
dVGL(j ny*i) = sin(acos(ygl[j]) * (i)); //this is correct
}
}
//##################################
dv1 = (dummy1) * (dVGL) * (dummy2); //this is incorrect, dVGL outside for loop is different from inside for loop!!
我已經為此絞盡腦汁一個星期了，我似乎無法解決它。為什么dVGL外面的for回圈不同？？（好像我的行和列的長度為 ny 1，但是當我展平陣列時，我只使用 ny。）這是為什么？
我覺得這應該是一個簡單的問題。
uj5u.com熱心網友回復：
感謝評論中的@chtz，我只需更改索引即可解決此問題：
dVGL(j (ny 1)*i) = sin(acos(ygl[j]) * (i));
dv1 = (dummy1) * (dVGL) * (dummy2); //Then this is correct
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