Resistor mesh: Difference between revisions

=={{Header|FreeBASIC}}==

<lang freebasic>' version 01-07-2018

' compile with: fbc -s console

#Define n 10

Dim As UInteger nn = n * n

Dim As Double g(-nn To nn +1, -nn To nn +1)

Dim As UInteger node, row, col

For row = 1 To n

For col = 1 To n

node += 1

If row > 1 Then

g(node, node) += 1

g(node, node - n) = -1

End If

If row < n Then

g(node, node) += 1

g(node, node + n) = -1

End If

If col > 1 Then

g(node, node) += 1

g(node, node -1) = -1

End If

If col < n Then

g(node, node) += 1

g(node, node +1) = -1

End If

Next

Next

Dim As UInteger ar = 2, ac = 2

Dim As UInteger br = 7, bc = 8

Dim As UInteger a = ac + n * (ar -1)

Dim As UInteger b = bc + n * (br -1)

g(a, nn +1) = -1

g(b, nn +1) = 1

Print : Print "Nodes a: "; a, " b: "; b

' solve linear system using Gauss-Seidel method with pivoting

Dim As UInteger i, j, k

Dim As Double y

Do

For j = 1 To nn

For i = j To nn

If g(i, j) <> 0 Then Exit For

Next

If i = nn +1 Then

Print : Print "No solution"

Exit Do

End If

For k = 1 To nn +1

Swap g(j, k), g(i, k)

Next

y = g(j, j)

For k = 1 To nn +1

g(j, k) = g(j, k) / y

Next

For i = 1 To nn

If i <> j Then

y = -g(i, j)

For k = 1 To nn +1

g(i, k) = g(i, k) + y * g(j, k)

Next

End If

Next

Next

Print

Print "Resistance ="; Abs(g(a, nn +1) - g(b, nn +1)); " Ohm"

Exit Do

Loop

' empty keyboard buffer

While Inkey <> "" : Wend

Print : Print "hit any key to end program"

Sleep

End</lang>

{{out}}

<pre>Nodes a: 12 b: 68

Resistance = 1.60899124173073 Ohm</pre>