Summation can be achieved in two ways&colon; "frequency summation" and "multiple fiber summation". The inverse DFT is a periodic summation of the original sequence. Neural binocular summation occurs when the binocular response is greater than the probability summation. This last summation is the harmonic series, which diverges. From this principle the error rules of summation, multiplication etc. In addition, the quotient difference becomes arbitrarily large as the summation index increases. This section uses Einstein notation, including Einstein summation convention. The summation is called a periodic summation of the function . Each term in the above summation is an individual Newtonian potential for a point mass. Reflections can cause acoustic problems such as phase summation and phase cancellation. The summation on is called a periodic summation of the function . To avoid this, approaches such as the Kahan summation algorithm are used. This is a version of the one-dimensional Poisson summation formula. The layers are Input, hidden, pattern/summation and output. Otherwise these operations can alter the result of summation.