Tableau Created; Basics: [-6, -5, -4, 5, 6, -1]
     1.0000000000   -20.0000000000    -1.0000000000                0                0                0                0                0     0.1000000000
     1.0000000000   -19.9000000000                0    -1.0000000000                0                0                0                0     0.1000000000
     0.1000000000                0                0                0    -1.0000000000                0                0                0     0.1000000000
     0.1000000000                0                0                0                0     1.0000000000                0                0     2.0000000000
                0     0.0000100000                0                0                0                0     1.0000000000                0 21474.8360000000
                0     0.0000100000                0                0                0                0                0    -1.0000000000     0.0000100000
                0                0                0                0                0                0                0                0                0
    -2.1000000000    39.8999900000     1.0000000000     1.0000000000     1.0000000000                0                0     1.0000000000    -0.3000100000

Needs Another Iteration? Phase=1 Artificials=4 Objective=-0.30001000000000005

findNextPivotCol (index of most negative value) among these:
[-2.1, 39.899989999999995, 1.0, 1.0, 1.0, 1.0]
Col: 0	=>	Reduced Contribution Weight: -2.1.

findNextPivotRow (smallest positive ratio) among these:
Numerators=[0.1, 0.1, 0.1, 2.0, 21474.83648, 1.0E-5]
Denominators=[1.0, 1.0, 0.1, 0.1, 0.0, 0.0]
Ratios=[0.1, 0.1, 1.0, 20.0, Infinity, Infinity]
Row: 0	=>	Ratio: 0.1,	Numerator/RHS: 0.1, 	Denominator/Pivot: 1.0.

==>>	Row: 0,	Exit: -6,	Column/Enter: 0.

Iteration Point <0,0>	Pivot: 1.0 => 1.0	RHS: 0.1 => 0.1.
Tableau Iteration; Basics: [0, -5, -4, 5, 6, -1]
     1.0000000000   -20.0000000000    -1.0000000000                0                0                0                0                0     0.1000000000
                0     0.1000000000     1.0000000000    -1.0000000000                0                0                0                0                0
                0     2.0000000000     0.1000000000                0    -1.0000000000                0                0                0     0.0900000000
                0     2.0000000000     0.1000000000                0                0     1.0000000000                0                0     1.9900000000
                0     0.0000100000                0                0                0                0     1.0000000000                0 21474.8360000000
                0     0.0000100000                0                0                0                0                0    -1.0000000000     0.0000100000
                0                0                0                0                0                0                0                0                0
                0    -2.1000100000    -1.1000000000     1.0000000000     1.0000000000                0                0     1.0000000000    -0.0900100000

Needs Another Iteration? Phase=1 Artificials=3 Objective=-0.09001000000000003

findNextPivotCol (index of most negative value) among these:
[-2.1000100000000046, -1.1, 1.0, 1.0, 1.0]
Col: 1	=>	Reduced Contribution Weight: -2.1000100000000046.

findNextPivotRow (smallest positive ratio) among these:
Numerators=[0.1, 0.0, 0.09, 1.99, 21474.83648, 1.0E-5]
Denominators=[-20.0, 0.10000000000000142, 2.0, 2.0, 1.0E-5, 1.0E-5]
Ratios=[-0.005, 0.0, 0.045, 0.995, 2.147483648E9, 1.0]
Row: 1	=>	Ratio: 0.0,	Numerator/RHS: 0.0, 	Denominator/Pivot: 0.10000000000000142.

==>>	Row: 1,	Exit: -5,	Column/Enter: 1.

Iteration Point <1,1>	Pivot: 0.10000000000000142 => 1.0	RHS: 0.0 => 0.0.
Tableau Iteration; Basics: [0, 1, -4, 5, 6, -1]
     1.0000000000                0   199.0000000000  -200.0000000000                0                0                0                0     0.1000000000
                0     1.0000000000    10.0000000000   -10.0000000000                0                0                0                0                0
                0                0   -19.9000000000    20.0000000000    -1.0000000000                0                0                0     0.0900000000
                0                0   -19.9000000000    20.0000000000                0     1.0000000000                0                0     1.9900000000
                0                0    -0.0001000000     0.0001000000                0                0     1.0000000000                0 21474.8360000000
                0                0    -0.0001000000     0.0001000000                0                0                0    -1.0000000000     0.0000100000
                0                0                0                0                0                0                0                0                0
                0                0    19.9001000000   -20.0001000000     1.0000000000                0                0     1.0000000000    -0.0900100000

Needs Another Iteration? Phase=1 Artificials=2 Objective=-0.09001000000000003

findNextPivotCol (index of most negative value) among these:
[19.900099999999746, -20.000099999999748, 1.0, 1.0]
Col: 3	=>	Reduced Contribution Weight: -20.000099999999748.

findNextPivotRow (smallest positive ratio) among these:
Numerators=[0.1, 0.0, 0.09, 1.99, 21474.83648, 1.0E-5]
Denominators=[-199.99999999999716, -9.999999999999858, 19.999999999999716, 19.999999999999716, 9.999999999999858E-5, 9.999999999999858E-5]
Ratios=[-5.000000000000072E-4, -0.0, 0.004500000000000064, 0.0995000000000014, 2.1474836480000305E8, 0.10000000000000142]
Row: 2	=>	Ratio: 0.004500000000000064,	Numerator/RHS: 0.09, 	Denominator/Pivot: 19.999999999999716.

==>>	Row: 2,	Exit: -4,	Column/Enter: 3.

Iteration Point <2,3>	Pivot: 19.999999999999716 => 1.0	RHS: 0.09 => 0.004500000000000064.
Tableau Iteration; Basics: [0, 1, 3, 5, 6, -1]
     1.0000000000                0                0                0   -10.0000000000                0                0                0     1.0000000000
                0     1.0000000000     0.0500000000                0    -0.5000000000                0                0                0     0.0450000000
                0                0    -0.9950000000     1.0000000000    -0.0500000000                0                0                0     0.0045000000
                0                0                0                0     1.0000000000     1.0000000000                0                0     1.9000000000
                0                0    -0.0000005000                0     0.0000050000                0     1.0000000000                0 21474.8360000000
                0                0    -0.0000005000                0     0.0000050000                0                0    -1.0000000000     0.0000095500
                0                0                0                0                0                0                0                0                0
                0                0     0.0000005000                0    -0.0000050000                0                0     1.0000000000    -0.0000095500

Needs Another Iteration? Phase=1 Artificials=1 Objective=-9.549999999899916E-6

findNextPivotCol (index of most negative value) among these:
[4.999999987376214E-7, -5.000000001587068E-6, 1.0]
Col: 4	=>	Reduced Contribution Weight: -5.000000001587068E-6.

findNextPivotRow (smallest positive ratio) among these:
Numerators=[0.9999999999999999, 0.045, 0.004500000000000064, 1.9, 21474.836479550002, 9.55E-6]
Denominators=[-10.0, -0.5, -0.05000000000000071, 1.0, 5.0E-6, 5.0E-6]
Ratios=[-0.09999999999999999, -0.09, -0.09, 1.9, 4.29496729591E9, 1.91]
Row: 3	=>	Ratio: 1.9,	Numerator/RHS: 1.9, 	Denominator/Pivot: 1.0.

==>>	Row: 3,	Exit: 5,	Column/Enter: 4.

Iteration Point <3,4>	Pivot: 1.0 => 1.0	RHS: 1.9 => 1.9.
Tableau Iteration; Basics: [0, 1, 3, 4, 6, -1]
     1.0000000000                0                0                0                0    10.0000000000                0                0    20.0000000000
                0     1.0000000000     0.0500000000                0                0     0.5000000000                0                0     0.9950000000
                0                0    -0.9950000000     1.0000000000                0     0.0500000000                0                0     0.0995000000
                0                0                0                0     1.0000000000     1.0000000000                0                0     1.9000000000
                0                0    -0.0000005000                0                0    -0.0000050000     1.0000000000                0 21474.8360000000
                0                0    -0.0000005000                0                0    -0.0000050000                0    -1.0000000000     0.0000000500
                0                0                0                0                0                0                0                0                0
                0                0     0.0000005000                0                0     0.0000050000                0     1.0000000000    -0.0000000500

Needs Another Iteration? Phase=1 Artificials=1 Objective=-4.999999688448698E-8

Switching to Phase2 with 1 artificial variable(s) still in the basis.

Reduced artificial costs:
[4.999999987376214E-7, 5.000000001587068E-6, 1.0]

findNextPivotCol (index of most negative value) among these:
[0.0, 0.0, 0.0]

==>>	No more iterations needed/possible.

!!!!!!!
!!!!!!!
Node solution marked as OPTIMAL, but is actually INVALID/INFEASIBLE/FAILED. Stop this branch!
0 (0) -1=NaN NaN [0=1<20, 1=-2147483648<-1]
Solutions=0 Nodes/Iterations=1 INVALID Infinity @ [0.0, 0.0]
############################################
1.000000 <= x <= 20.000000
-2147483648.000000 <= y <= -1.000000
inequality_2: 0.0 <= -1.000000
inequality_1: 0.0 <= -1.000000
############################################

[SNIP: I removed the output from the second run of the LinearSolver, see my mail]

<Builder>
[AE] = org.ojalgo.matrix.PrimitiveMatrix < 6 x 8 >
{ { 1.0,	-20.0,	-1.0,	0.0,	0.0,	0.0,	0.0,	0.0 },
{ 1.0,	-19.9,	0.0,	-1.0,	0.0,	0.0,	0.0,	0.0 },
{ 0.1,	0.0,	0.0,	0.0,	-1.0,	0.0,	0.0,	0.0 },
{ 0.1,	0.0,	0.0,	0.0,	0.0,	1.0,	0.0,	0.0 },
{ 0.0,	1.0E-5,	0.0,	0.0,	0.0,	0.0,	1.0,	0.0 },
{ 0.0,	1.0E-5,	0.0,	0.0,	0.0,	0.0,	0.0,	-1.0 } }
[BE] = org.ojalgo.matrix.PrimitiveMatrix < 6 x 1 >
{ { 0.1 },
{ 0.1 },
{ 0.1 },
{ 2.0 },
{ 21474.83648 },
{ 1.0E-5 } }
[Q] = ?
[C] = org.ojalgo.matrix.PrimitiveMatrix < 8 x 1 >
{ { 0.0 },
{ 0.0 },
{ 0.0 },
{ 0.0 },
{ 0.0 },
{ 0.0 },
{ 0.0 },
{ 0.0 } }
[AI] = ?
[BI] = ?
[X] = org.ojalgo.matrix.PrimitiveMatrix < 8 x 1 >
{ { 20.0 },
{ 0.995 },
{ 0.0 },
{ 0.0995000000000014 },
{ 1.9 },
{ 0.0 },
{ 21474.836470050002 },
{ 0.0 } }
[LE] = org.ojalgo.matrix.PrimitiveMatrix < 6 x 1 >
{ { 0.0 },
{ 0.0 },
{ 0.0 },
{ 0.0 },
{ 0.0 },
{ 0.0 } }
[LI] = org.ojalgo.matrix.PrimitiveMatrix < 0 x 1 >
[SE] = org.ojalgo.matrix.PrimitiveMatrix < 6 x 1 >
{ { -1.4155343563970746E-15 },
{ 9.575673587391975E-16 },
{ -8.326672684688674E-17 },
{ 0.0 },
{ 0.0 },
{ 4.999999999999952E-8 } }
[SI] = ?
</Builder>
