YAPC::EU 2018 Glasgow Update!

Task/Resistor-mesh/FreeBASIC/resistor-mesh.freebasic

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+' 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