random: fix rounding in barand()

This fixes #85.

* src/misc/random.hh (barand): Use round() before casting.
* doc/org/oaut.org: Recompute example.
* src/tests/randaut.test, wrap/python/tests/randaut.ipynb: Adjust.

doc/org/oaut.org

@@ -866,29 +866,27 @@ In most tools =%F= and =%L= are the input filename and line number,
 but as this makes no sense in =randaut=, these two sequences emit
 numbers related to the generation of automata.
 
-For instance let's generate 100 random automata with 10 states and
+For instance let's generate 1000 random automata with 100 states and
 density 0.2, and just count the number of edges in each automaton. Then
 use =R= to summarize the distribution of these values:
 
 #+BEGIN_SRC sh :results verbatim :exports both
-randaut -d0.2 -Q10 -n1000 a --stats %e > size.csv
+randaut -d0.2 -Q100 -n1000 a --stats %e > size.csv
 R --slave -e "summary(read.csv('size.csv', header=FALSE, col.names='edges'))"
 #+END_SRC
 
 #+RESULTS:
 :      edges
-:  Min.   :14.00
-:  1st Qu.:22.00
-:  Median :25.00
-:  Mean   :24.72
-:  3rd Qu.:27.00
-:  Max.   :36.00
-
-
-For $Q=10$ states and density $D=0.2$ the expected degree of each
-state is $1+(Q-1)D = 1+9\times 0.2 = 2.8$, so the expected number of
-edges should be 10 times that.
+:  Min.   :1939
+:  1st Qu.:2056
+:  Median :2083
+:  Mean   :2082
+:  3rd Qu.:2107
+:  Max.   :2233
 
+For $Q=100$ states and density $D=0.2$ the expected degree of each
+state is $1+(Q-1)D = 1+99\times 0.2 = 20.8$, so the expected number of
+edges should be $20.8\times100=2080$.
 
 * Naming automata
 

src/misc/random.hh

@@ -23,6 +23,7 @@
 #pragma once
 
 #include "common.hh"
+#include <cassert>
 #include <cmath>
 #include <vector>
 
@@ -72,7 +73,7 @@ namespace spot
 
   /// \brief Compute pseudo-random integer value between 0
   /// and \a n included, following a binomial distribution
-  /// for probability \a p.
+  /// with probability \a p.
   ///
   /// \a gen must be a random function computing a pseudo-random
   /// double value following a standard normal distribution.
@@ -93,18 +94,16 @@ namespace spot
     int
     rand() const
     {
-      int res;
-
       for (;;)
 	{
-	  double x = gen() * s_ + m_;
-	  if (x < 0.0)
+	  int x = round(gen() * s_ + m_);
+	  if (x < 0)
 	    continue;
-	  res = static_cast<int> (x);
-          if (res <= n_)
-	    break;
+          if (x <= n_)
+	    return x;
         }
-      return res;
+      SPOT_UNREACHABLE();
+      return 0;
     }
   protected:
     const int n_;

src/tests/randaut.test

@@ -59,10 +59,10 @@ test `expr $a + $b` = 100
 $randaut -n 5 --name='%F-%L-%s-%c-%e' -H a | grep '^name' >out
 cat >expected<<EOF
 name: "0-0-10-1-30"
-name: "0-1-10-4-27"
-name: "0-2-10-6-20"
-name: "0-3-10-1-25"
-name: "0-4-10-2-20"
+name: "0-1-10-1-29"
+name: "0-2-10-3-22"
+name: "0-3-10-1-30"
+name: "0-4-10-1-27"
 EOF
 diff out expected
 
@@ -97,19 +97,19 @@ $a: 4 Inf(0)&Inf(1)&Inf(2)&Inf(3)
 acc-name: generalized-Buchi 4
 $a: 4 Inf(0)&Inf(1)&Inf(2)&Inf(3)
 $a: 4 Fin(1) | (Fin(2) & Fin(3) & Fin(0))
-$a: 4 Inf(2) | ((Inf(0) | Inf(1)) & Fin(3))
+$a: 4 (Fin(0) & Fin(3)) | (Fin(2) & Inf(1))
 acc-name: parity min even 4
 $a: 4 Inf(0) | (Fin(1) & (Inf(2) | Fin(3)))
-acc-name: parity max odd 3
-$a: 3 Fin(2) & (Inf(1) | Fin(0))
-acc-name: parity max even 3
-$a: 3 Inf(2) | (Fin(1) & Inf(0))
+acc-name: parity max even 2
+$a: 2 Fin(1) & Inf(0)
+acc-name: parity max odd 4
+$a: 4 Inf(3) | (Fin(2) & (Inf(1) | Fin(0)))
+acc-name: generalized-Rabin 3 2 3 0
+$a: 8 (Fin(0) & (Inf(1)&Inf(2))) | (Fin(3) & (Inf(4)&Inf(5)&Inf(6))) | Fin(7)
+acc-name: generalized-Rabin 3 2 2 0
+$a: 7 (Fin(0) & (Inf(1)&Inf(2))) | (Fin(3) & (Inf(4)&Inf(5))) | Fin(6)
 acc-name: generalized-Rabin 3 2 3 0
 $a: 8 (Fin(0) & (Inf(1)&Inf(2))) | (Fin(3) & (Inf(4)&Inf(5)&Inf(6))) | Fin(7)
-acc-name: generalized-Rabin 3 1 2 0
-$a: 6 (Fin(0) & Inf(1)) | (Fin(2) & (Inf(3)&Inf(4))) | Fin(5)
-acc-name: generalized-Rabin 3 1 3 0
-$a: 7 (Fin(0) & Inf(1)) | (Fin(2) & (Inf(3)&Inf(4)&Inf(5))) | Fin(6)
 EOF
 diff output expected
 
@@ -122,14 +122,14 @@ $randaut -n 10 2..4 -H | grep AP: > output
 cat output
 cat >expected <<EOF
 AP: 3 "p0" "p1" "p2"
+AP: 4 "p0" "p1" "p2" "p3"
 AP: 3 "p0" "p1" "p2"
-AP: 3 "p0" "p1" "p2"
-AP: 3 "p0" "p1" "p2"
+AP: 4 "p0" "p1" "p2" "p3"
 AP: 3 "p0" "p1" "p2"
 AP: 4 "p0" "p1" "p2" "p3"
 AP: 2 "p0" "p1"
 AP: 3 "p0" "p1" "p2"
 AP: 2 "p0" "p1"
-AP: 4 "p0" "p1" "p2" "p3"
+AP: 3 "p0" "p1" "p2"
 EOF
 diff output expected