But sum(sum(A)) requires that you know the dimension of your array is 2. Using the sum of all elements does not contain any information about endomorphisms, which is the reason why you will not find such an operation in the literature. I tried the largest size allowed on my computer a few more times. So if you have similar experience with Matlab timers, none of the tests can discern sum(A(:)) and sum(sum(A)). In my experience, both timers are only meaningful up to. If A is a matrix, the expression A+n is evaluated by adding n to each element of A. When add/subtract a scalar to an array, MATLAB adds / subtracts the scalar to every element of the array. The cputime for sum(sum(A)) in seconds is A scalar may be added to a matrix of any dimension. Learn more about element, every-other, matrix. In each test, A=rand(size) and size is specified in the displayed texts. It is likely that they hard-code sum(sum(A)) to be a single loop, the same to sum(A(:)).īelow I offer some testing results. But I think sum(sum(A)) is very wide-spread amongst users. Step 4: If max < array element value change max to new. It would be slower if Matlab actually creates a row vector recording the sum of each column of A first and then sum over the columns. 2000+ Algorithm Examples in Python, Java, Javascript, C, C++, Go, Matlab, Kotlin, Ruby, R and Scala. If it is, then we have a reason to believe that the shape of an array is not directly related to the way the data is stored and manipulated.)Īs such, there is no reason sum(sum(A)) should be faster. Matrix form of a SLE Every SLE can be written in the matrix notation: L 5 5 5 5, L T 5 T, L > 5 >, Matrix of coefficients of the SLE (of size H ). (One can test reshape() and check if reshaping is fast in Matlab. So the shape of A does not quite matter in sum(). In my experience, arrays in Matlab seems to be stored in a continuous block in memory as stacked column vectors. In which case, the sum of two matrices A and B will be a matrix which has the same. The best practice is definitely to avoid loops or recursions in Matlab. Two matrices must have an equal number of rows and columns to be added.