> ## Documentation Index
> Fetch the complete documentation index at: https://docs.ntop.com/llms.txt
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# Number of degrees of freedom in LHS and RHS aren't equal

## Issue:

I ran an analysis, and this error came up: "Error in solving the linear system of equations. Number of degrees of freedom in LHS and RHS aren't equal"

## Applies to:

* Simulation
* Topology Optimization

## Cause:

The cause for this issue is typically due to an error in a boundary condition or a constraint block.

## Solution:

* * Adjust the the tolerances for each boundary condition and ensure they all make sense and work?
    * The nodes might be part of dependent nodes of a Tie Constraint (that theoretically will have to follow the independent nodes),
    * Make sure the constraint and restraint blocks are used correctly in Topology Optimizations
      * Ensure that there are no same nodes in a Displacement Restraint (that theoretically will be fixed (if the value is 0) or have a Prescribed Displacement (if the value is non-zero))

## Keywords:

*error analysis simulation system topology of linear issue degrees freedom aren't equal lhs rhs*