MATLAB: What is the efficient method for solving symbolic system of equation

linear equationmemorysymbolic

Dear all,
now I am using the inverse of matrice x=inv(A)*b and A\b but it does not efficiently solve with large problem. the problem is the error of using mupadmex in command sym for inverse matrices is out of memory. so anyone could suggest me what is the best method for solving the symbolic system of equation?
thank you so much. Best regard
Chantrea

Best Answer

Symbolic solutions of larger matrices are inherently large. For example the inverse of a 5 x 5 matrix is over 200000 characters long, and 6 x 6 is over 2000000 long; each additional increment makes the inverse about 10 times larger to represent on output -- and additional memory might be required during the calculation. Multiple gigabytes to calculate the 7 x 7. Roughly 2.2 * 10^N is the output size for the symbolic inverse of a matrix N x N.
If you do not have that much memory, then either add physical memory or add "swap" (which will likely be very slow unless you are using solid state disks).
There is no "compact" or "memory efficient" symbolic inverse. Symbolic solutions are exact solutions and every portion of the solution is needed to get the right answer. You might be able to simplify() afterwards but the sizes I list above are after simplification.
What size of matrix are you trying to process?
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