Calculate the eigenvalues of many 3x3 real symmetric matrices.-Calculate the eigenvalues of many 3x3 real symmetric matrices. Computation is non-iterative, based on fully vectorized matlab matrix operations, and GPU computation is supported. It is fast and efficient for processing a number of 3-by-3 matrices at once. This code particularly suits tensor/Riemannian calculus in 3D, visualization/analysis of volumetric tensor images, image Jacobian/Hessian analysis, stress/tensile strength computation on tensor fields, three dimensional diffusion processes, determining the rotation axes of a motion field, etc....