Initial data commit

Task/Resistor-mesh/Nim/resistor-mesh.nim

@@ -0,0 +1,73 @@
+const S = 10
+
+type
+
+  NodeKind = enum nodeFree, nodeA, nodeB
+
+  Node = object
+    v: float
+    fixed: NodeKind
+
+  Mesh[H, W: static int] = array[H, array[W, Node]]
+
+
+func setBoundary(m: var Mesh) =
+  m[1][1].v =  1.0
+  m[1][1].fixed = nodeA
+  m[6][7].v = -1.0
+  m[6][7].fixed = nodeB
+
+
+func calcDiff[H, W: static int](m,: Mesh[H, W]; d: var Mesh[H, W]): float =
+  for i in 0..<H:
+    for j in 0..<W:
+      var v = 0.0
+      var n = 0
+      if i > 0:
+        v += m[i - 1][j].v
+        inc n
+      if j > 0:
+        v += m[i][j - 1].v
+        inc n
+      if i + 1 < m.H:
+        v += m[i + 1][j].v
+        inc n
+      if j + 1 < m.W:
+        v += m[i][j + 1].v
+        inc n
+      v = m[i][j].v - v / n.toFloat
+      d[i][j].v = v
+      if m[i][j].fixed == nodeFree:
+        result += v * v
+
+
+func iter[H, W: static int](m: var Mesh[H, W]): float =
+  var
+    d: Mesh[H, W]
+    cur: array[NodeKind, float]
+    diff = 1e10
+
+  while diff > 1e-24:
+    m.setBoundary()
+    diff = calcDiff(m, d)
+    for i in 0..<H:
+      for j in 0..<W:
+        m[i][j].v -= d[i][j].v
+
+  for i in 0..<H:
+    for j in 0..<W:
+      var k = 0
+      if i != 0: inc k
+      if j != 0: inc k
+      if i < m.H - 1: inc k
+      if j < m.W - 1: inc k
+      cur[m[i][j].fixed] += d[i][j].v * k.toFloat
+
+  result = (cur[nodeA] - cur[nodeB]) / 2
+
+
+when isMainModule:
+
+  var mesh: Mesh[S, S]
+  let r = 2 / mesh.iter()
+  echo "R = ", r