SetDirectory[NotebookDirectory[]]

data=Import["A.txt","Table"];

Dimensions[data]

data[[1;;3]]

d=Drop[data,3];

m = 4194;

A=Table[0.,{i,m},{j,m}];

Dimensions[A]

Length[d]

d[[46356,1]]

For[k=1, k< Length[d], k++,A[[ d[[k,1]]+1, d[[k,2]]+1 ]] = d[[k,3]] ];

Norm[A - Transpose[A]]

Dimensions[A]

Export["A.mat",A]