add missing file

src/observables/sources.nim

@@ -0,0 +1,18 @@
+import field, comms/comms
+
+proc wallSource*(f: Field, t0: int, v: auto) =
+  for i in f.l.sites:
+    let t = f.l.coords[^1][i]
+    if t == t0:
+      f{i} := v
+
+proc norm2slice*(f: SomeField, s: int): seq[float] =
+  #for i in l:
+  #  let t = l.vcoords[3][i][0]
+  let ns = f.l.physGeom[s]
+  var c = newSeq[float](ns)
+  for i in f.sites:
+    let k = f.l.coords[s][i]
+    c[k] += f{i}.norm2
+  threadRankSum c
+  c