luby sequence generator; can use to plot MiniSat's restart sequence

diff --git a/contrib/Makefile.am b/contrib/Makefile.am
index 1dd5c8ded7d318b9ff89840a4c65a45731a159c1..42e3b6f9fa257141545c4c89d2b4f60af976c060 100644 (file)
--- a/contrib/Makefile.am
+++ b/contrib/Makefile.am
@@ -5,5 +5,6 @@ EXTRA_DIST = \
        switch-config \
        cvc-mode.el \
        editing-with-emacs \
+       luby.c \
        configure-in-place \
        depgraph

diff --git a/contrib/luby.c b/contrib/luby.c
new file mode 100644 (file)
index 0000000..71b07b6
--- /dev/null
+++ b/contrib/luby.c
@@ -0,0 +1,69 @@
+// luby.c - Luby sequence generator
+// Morgan Deters <mdeters@cs.nyu.edu> for the CVC4 project, 5 May 2011
+//
+// This program enumerates the Luby-based MiniSat 2 restart sequence.
+// MiniSat restarts after a number of conflicts determined by:
+//
+//    restart_base * luby(restart_inc, curr_restarts)
+//
+// By default, MiniSat has restart_base = 25, restart_inc = 3.0, and
+// curr_restarts is the number of restarts that have been done (so it
+// starts at 0).
+//
+// For the Luby paper, see:
+//   http://citeseer.ist.psu.edu/viewdoc/summary?doi=10.1.1.47.5558
+//
+// Compile luby.c with gcc -o luby luby.c -lm
+//
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <assert.h>
+#include <math.h>
+
+// luby() function copied from MiniSat 2
+// Copyright (c) 2003-2006, Niklas Een, Niklas Sorensson
+// Copyright (c) 2007-2010, Niklas Sorensson
+double luby(double y, int x){
+
+    // Find the finite subsequence that contains index 'x', and the
+    // size of that subsequence:
+    int size, seq;
+    for (size = 1, seq = 0; size < x+1; seq++, size = 2*size+1);
+
+    while (size-1 != x){
+        size = (size-1)>>1;
+        seq--;
+        x = x % size;
+    }
+
+    return pow(y, seq);
+}
+
+int main(int argc, char *argv[]) {
+  int N;
+  int base;
+  double inc;
+  int i;
+
+  if(argc != 4) {
+    fprintf(stderr, "usage: %s base inc N\n"
+            "In MiniSat 2, base==25 and inc==3 by default.\n"
+            "base is simply a multiplier after the sequence is computed.\n"
+            "N is the number to produce (-1 means run until CTRL-C)\n",
+            argv[0]);
+    exit(1);
+  }
+
+  base = atoi(argv[1]);
+  inc = strtod(argv[2], NULL);
+  N = atoi(argv[3]);
+
+  assert(base >= 1);
+  assert(inc >= 1.0);
+
+  for(i = 0; N < 0 || i < N; ++i) {
+    printf("%d %f\n", i, luby(inc, i) * base);
+  }
+}