So far I think the most stupid mistake I made was to confuse the iteration of a matrix row by row with as column by column.

Was a few months. It had to implement the Jacobi algorithm to compute eigenvalues ​​and eigenvectors of symmetric matrices.
To verify that the calculations were done correctly I assessed that satisfy A * V = Lambda * V and V is orthonormal.

I Had two algorithms: one as a control and the other with some improvements but in essence were almost identical. For some reason the control worked perfectly, but the other told me that no tests passed and the results differed in some decimals.

I examined the code of Jacobi line by line looking for the culprit and everything was in order . I had even come to think that I was altering some compiler directive or changed the data type ... And nothing ... everything was OK.


I was two weeks sitting in front of the monitor ... The error was that when submitting data did eigenvectors of rows and columns as it should not. All for a variable and a cycle.
Since then I have stuck a post-it on my monitor that reminds me not confuse rows and columns.

Regards,
P.S: Sorry for my poor English.