In[]:=
Needs["NDSolve`FEM`"]​​mesh=ToElementMesh[FullRegion[2],{{0,1},{0,1}},MaxCellMeasure10^-3]
Out[]=
ElementMesh[{{0.,1.},{0.,1.}},{QuadElement[<1024>]}]
In[]:=
Do[sol[i]=​​NDSolveValue[{Laplacian[u[x,y],{x,y}]+1==0,​​DirichletCondition[u[x,y]==0,True]},u,Element[{x,y},mesh]];,{i,10}]​​​​Table[sol[1][6/10,6/10]-sol[i][6/10,6/10],{i,10}]
Out[]=
{0.,1.52656×
-16
10
,1.52656×
-16
10
,1.52656×
-16
10
,-1.38778×
-17
10
,1.52656×
-16
10
,4.16334×
-17
10
,1.52656×
-16
10
,1.52656×
-16
10
,1.52656×
-16
10
}
​
Out[]=
{0.,1.66533×
-16
10
,1.66533×
-16
10
,1.66533×
-16
10
,1.66533×
-16
10
,1.80411×
-16
10
,1.66533×
-16
10
,1.66533×
-16
10
,0.,1.80411×
-16
10
}
​
Out[]=
{0.,4.16334×
-17
10
,4.16334×
-17
10
,4.16334×
-17
10
,4.16334×
-17
10
,4.16334×
-17
10
,4.16334×
-17
10
,4.16334×
-17
10
,-1.38778×
-16
10
,4.16334×
-17
10
}