# FastDiffusionSolver2D¶

Note

The current implementation of DiffusionSolverFE may actually be faster than this legacy module. So before commiting to it please verify the performance of teh DiffusionSolverFE vs FastDiffusionSolverFE

FastDiffusionSolver2DFE module is a simplified version of the FlexibleDiffusionSolverFE steppable. It runs several times faster that flexible solver but lacks some of its features. Typical syntax is shown below:

<Steppable Type="FastDiffusionSolver2DFE">
<DiffusionField Name="FGF">
<DiffusionData>
<UseBoxWatcher/>
<FieldName>FGF</FieldName>
<DiffusionConstant>0.010</DiffusionConstant>
<DecayConstant>0.003</DecayConstant>
<ExtraTimesPerMCS>2</ExtraTimesPerMCS>
<DoNotDecayIn>Wall</DoNotDecay>
<ConcentrationFileName>Demos/diffusion/diffusion_2D_fast_box.pulse.txt
</ConcentrationFileName>
</DiffusionData>
</DiffusionField>
</Steppable>


In particular, for fast solver you cannot specify cells into which diffusion is prohibited. However, you may specify cell types where diffusant decay is prohibited

For explanation on how <ExtraTimesPerMCS> tag works works see section on FlexibleDiffusionSolverFE.