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ChangeLog

@@ -1,3 +1,9 @@
+2010-08-29 Dietmar Warning
+ * fteext.h, parse.c, cmath2.c, cmath2.h,: 
+   new function sunif(), uniform random generator usable in control blocks
+ * examples/control_structs/MonteCarlo.sp: Simple example to perform MC runs
+   in ngspice using uniform and gaussian distributions
+
 2010-08-29  Holger Vogt
  * fteext.h, main.c, randnumb.c, parse.c, cmath2.c, cmath2.h: 
    new function sgauss(), new random number generator with very

examples/control_structs/MonteCarlo.sp

@@ -0,0 +1,49 @@
+Perform Monte Carlo simulation in ngspice
+V1 N001 0 AC 1 DC 0
+R1 N002 N001 141
+*
+C1 OUT 0 1e-09
+L1 OUT 0 10e-06
+C2 N002 0 1e-09
+L2 N002 0 10e-06
+L3 N003 N002 40e-06
+C3 OUT N003 250e-12
+*
+R2 0 OUT 141
+*
+.control
+  let mc_runs = 100
+  let run = 1
+  set curplot = new       $ create a new plot
+  set scratch = $curplot  $ store its name to 'scratch'
+*
+  define unif(nom, var) (nom + (nom*var) * sunif(0))
+  define aunif(nom, avar) (nom + avar * sunif(0))
+  define gauss(nom, var, sig) (nom + (nom*var)/sig * sgauss(0))
+  define agauss(nom, avar, sig) (nom + avar/sig * sgauss(0))
+*
+  dowhile run <= mc_runs
+*    alter c1 = unif(1e-09, 0.1)
+*    alter l1 = aunif(10e-06, 2e-06)
+*    alter c2 = aunif(1e-09, 100e-12)
+*    alter l2 = unif(10e-06, 0.2)
+*    alter l3 = aunif(40e-06, 8e-06)
+*    alter c3 = unif(250e-12, 0.15)
+    alter c1 = gauss(1e-09, 0.1, 3)
+    alter l1 = agauss(10e-06, 2e-06, 3)
+    alter c2 = agauss(1e-09, 100e-12, 3)
+    alter l2 = gauss(10e-06, 0.2, 3)
+    alter l3 = agauss(40e-06, 8e-06, 3)
+    alter c3 = gauss(250e-12, 0.15, 3)
+    ac oct 100 250K 10Meg
+    set run ="$&run"     $ create a variable from the vector
+    set dt = $curplot    $ store the current plot to dt
+    setplot $scratch     $ make 'scratch' the active plot
+    let vout{$run}={$dt}.v(out) $ store the output vector to plot 'scratch'
+    setplot $dt          $ go back to the previous plot
+    let run = run + 1 
+  end
+  plot db({$scratch}.all)
+.endc
+
+.end