examples: add simple multi_nc example

src/examples/multi_nc.nim

@@ -0,0 +1,72 @@
+import qex, gauge/stoutsmear
+
+qexInit()
+
+let
+  seed = 4321u
+  lat = @[8,8,8,16]
+  nd = lat.len
+  lo = lat.newLayout
+  vol = lo.physVol
+  gc = GaugeActionCoeffs(plaq: 6.0)
+
+var r = lo.newRNGField(RngMilc6, seed)
+
+var gaugeu1 = newseq[Field[VLEN,Color[MatrixArray[1,1,DComplexV]]]](nd)
+var gaugesu2 = newseq[Field[VLEN,Color[MatrixArray[2,2,DComplexV]]]](nd)
+var gaugesu3= newseq[Field[VLEN,Color[MatrixArray[3,3,DComplexV]]]](nd)
+for i in 0..<nd:
+  gaugeu1[i].new lo
+  gaugesu2[i].new lo
+  gaugesu3[i].new lo
+
+var fu1 = gaugeu1.newOneOf
+var fsu2 = gaugesu2.newOneOf
+var fsu3 = gaugesu3.newOneOf
+
+threads:
+  gaugeu1.random r
+  gaugesu2.random r
+  gaugesu3.random r
+
+var eps = 0.1
+for n in 0..<3:
+  gc.gaugeForce(gaugeu1, fu1)
+  gc.gaugeForce(gaugesu2, fsu2)
+  gc.gaugeForce(gaugesu3, fsu3)
+  threads:
+    for mu in 0..<nd:
+      for s in gaugeu1[mu]:
+        gaugeu1[mu][s] := exp((-eps)*fu1[mu][s])*gaugeu1[mu][s]
+      for s in gaugesu2[mu]:
+        gaugesu2[mu][s] := exp((-eps)*fsu2[mu][s])*gaugesu2[mu][s]
+      for s in gaugesu3[mu]:
+        gaugesu3[mu][s] := exp((-eps)*fsu3[mu][s])*gaugesu3[mu][s]
+
+echo gc.gaugeAction1(gaugeu1)
+echoPlaq gaugeu1
+echo gc.gaugeAction1(gaugesu2)
+echoPlaq gaugesu2
+echo gc.gaugeAction1(gaugesu3)
+echoPlaq gaugesu3
+
+
+proc fnorm2(f: auto): float =
+  var s:float
+  threads:
+    var t = 0.0
+    for i in 0..<nd:
+      t += f[i].norm2
+    threadSingle:
+      s = t
+  s
+
+echo gaugeu1.fnorm2-float(4*vol)
+echo gaugesu2.fnorm2-float(2*4*vol)
+echo gaugesu3.fnorm2-float(3*4*vol)
+
+echo fu1.fnorm2
+echo fsu2.fnorm2
+echo fsu3.fnorm2
+
+qexFinalize()