Platform: All Platforms Applies to: COMSOL Multiphysics® Versions: All versions

Problem Description

The error "Out of memory during assembly" occurs.


This error message indicates that your computer does not have enough RAM memory to assemble the numerical model which you are working with. There are two distinct, sequential, memory-intensive steps that occur when you compute the solution:

  • Assembly: During assembly, the software takes the information about the model, the mesh, the physics (material properties, boundary conditions, etc.) and assembles a large system of equations.

  • Solving: During the solving step, the software solves the set of equations that has been assembled. This step will almost always require more memory than the assembly step.

If you run out of memory during the assembly step, you do not have enough RAM memory in your computer to solve your model. Follow the guidance given in Knowledge Base 1030: Error: "Out of memory"

If your model includes integration coupling operators, this may also cause COMSOL to run out of memory during the assembly step. For example, defining a heat source based on an integration operator over the whole domain that is also a function of temperature (the dependent variable) leads to a coupling between all the degrees of freedom in the model. This leads to a full Jacobian matrix instead of the sparse limited-bandwidth matrices typical of finite element models. For advice on how to work around this issue please refer to the section Nonlocal Couplings and The Sparsity of the Jacobian in the COMSOL Multiphysics Reference Manual.

See also: Knowledge Base 1243: Out of memory