  The exact evaluation of the disconnected diagram contributions to the
flavor-singlet pseudoscalar meson mass, the nucleon sigma term and the nucleon
electromagnetic form factors, is carried out utilizing GPGPU technology with
the NVIDIA CUDA platform. The disconnected loops are also computed using
stochastic methods with several noise reduction techniques. Various dilution
schemes as well as the truncated solver method are studied. We make a
comparison of these stochastic techniques to the exact results and show that
the number of noise vectors depends on the operator insertion in the fermionic
loop.
