sn-pairwise: Implement the pairwise sorting network.

diff --git a/README b/README
index 86f7733..3778dde 100644 (file)
--- a/README
+++ b/README
@@ -45,9 +45,16 @@ The distribution includes the following utility programs:
     way.
 
   * sn-oddevenmerge
     way.
 
   * sn-oddevenmerge

-    Creates a odd-even-merge-sort network with a given number of inputs and
+    Create an odd-even merge network with a given number of left and right
+    inputs. The resulting network is printed to STDOUT.
+
+  * sn-oddevensort
+    Creates an odd-even mergesort network with a given number of inputs and

     prints the network to STDOUT.
 
     prints the network to STDOUT.
 

+  * sn-pairwise
+    Create a pairwise sorting network based on the paper by Ian Parberry.
+

   * sn-shmoo
     Prints a so-called "shmoo chart" of a comparator network to STDOUT. The
     running time of this tool is exponential, roughly O(m * 2^n) where m is the
   * sn-shmoo
     Prints a so-called "shmoo chart" of a comparator network to STDOUT. The
     running time of this tool is exponential, roughly O(m * 2^n) where m is the

diff --git a/src/Makefile.am b/src/Makefile.am
index fb28f66..e30ca07 100644 (file)
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -4,7 +4,7 @@ lib_LTLIBRARIES = libsortnetwork.la
 
 bin_PROGRAMS = sn-apply sn-batcher sn-bb sn-bb-merge sn-check-bf sn-cut \
               sn-info sn-markov sn-merge sn-normalize \
 
 bin_PROGRAMS = sn-apply sn-batcher sn-bb sn-bb-merge sn-check-bf sn-cut \
               sn-info sn-markov sn-merge sn-normalize \

-              sn-oddevenmerge sn-oddevensort \
+              sn-oddevenmerge sn-oddevensort sn-pairwise \

               sn-shmoo sn-show sn-svg sn-tex
 
 libsortnetwork_la_SOURCES = sn_network.c sn_network.h       \
               sn-shmoo sn-show sn-svg sn-tex
 
 libsortnetwork_la_SOURCES = sn_network.c sn_network.h       \


@@ -50,6 +50,9 @@ sn_oddevenmerge_LDADD = libsortnetwork.la
 sn_oddevensort_SOURCES = sn-oddevensort.c
 sn_oddevensort_LDADD = libsortnetwork.la
 
 sn_oddevensort_SOURCES = sn-oddevensort.c
 sn_oddevensort_LDADD = libsortnetwork.la
 

+sn_pairwise_SOURCES = sn-pairwise.c
+sn_pairwise_LDADD = libsortnetwork.la
+

 sn_shmoo_SOURCES = sn-shmoo.c
 sn_shmoo_LDADD = libsortnetwork.la
 
 sn_shmoo_SOURCES = sn-shmoo.c
 sn_shmoo_LDADD = libsortnetwork.la
 

diff --git a/src/sn-pairwise.c b/src/sn-pairwise.c
new file mode 100644 (file)
index 0000000..99079d5
--- /dev/null
+++ b/src/sn-pairwise.c
@@ -0,0 +1,64 @@
+/**
+ * libsortnetwork - src/sn-pairwise.c
+ * Copyright (C) 2008-2010  Florian octo Forster
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the
+ * Free Software Foundation; only version 2 of the License is applicable.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write to the Free Software Foundation, Inc.,
+ * 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
+ *
+ * Authors:
+ *   Florian octo Forster <ff at octo.it>
+ **/
+
+#ifndef _ISOC99_SOURCE
+# define _ISOC99_SOURCE
+#endif
+#ifndef _POSIX_C_SOURCE
+# define _POSIX_C_SOURCE 200112L
+#endif
+
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "sn_network.h"
+
+int main (int argc, char **argv)
+{
+  sn_network_t *n;
+  size_t inputs_num;
+
+  if (argc != 2)
+  {
+    printf ("Usage: %s <num inputs>\n", argv[0]);
+    return (0);
+  }
+
+  inputs_num = (size_t) atoi (argv[1]);
+  if (inputs_num < 2)
+  {
+    fprintf (stderr, "Invalid number of inputs: %zu\n", inputs_num);
+    return (1);
+  }
+
+  n = sn_network_create_pairwise (inputs_num);
+  if (n == NULL)
+  {
+    printf ("n == NULL!\n");
+    return (1);
+  }
+
+  sn_network_write (n, stdout);
+
+  return (0);
+} /* int main */
+
+/* vim: set shiftwidth=2 softtabstop=2 : */

diff --git a/src/sn_network.c b/src/sn_network.c
index b490de4..1b3dd36 100644 (file)
--- a/src/sn_network.c
+++ b/src/sn_network.c
@@ -135,6 +135,78 @@ sn_network_t *sn_network_create_odd_even_mergesort (int inputs_num) /* {{{ */
   }
 } /* }}} sn_network_t *sn_network_create_odd_even_mergesort */
 
   }
 } /* }}} sn_network_t *sn_network_create_odd_even_mergesort */
 

+static int sn_network_create_pairwise_internal (sn_network_t *n, /* {{{ */
+    int *inputs, int inputs_num)
+{
+  int i;
+  int inputs_copy[inputs_num];
+  int m;
+
+  for (i = 1; i < inputs_num; i += 2)
+  {
+    sn_comparator_t *c = sn_comparator_create (inputs[i-1], inputs[i]);
+    sn_network_comparator_add (n, c);
+    sn_comparator_destroy (c);
+  }
+
+  if (inputs_num <= 2)
+    return (0);
+
+  /* Sort "pairs" recursively. Like with odd-even mergesort, odd and even lines
+   * are handled recursively and later reunited. */
+  for (i = 0; i < inputs_num; i += 2)
+    inputs_copy[(int) (i / 2)] = inputs[i];
+  /* Recursive call #1 with first set of lines */
+  sn_network_create_pairwise_internal (n, inputs_copy,
+      (int) ((inputs_num + 1) / 2));
+
+  for (i = 1; i < inputs_num; i += 2)
+    inputs_copy[(int) (i / 2)] = inputs[i];
+  /* Recursive call #2 with second set of lines */
+  sn_network_create_pairwise_internal (n, inputs_copy,
+      (int) (inputs_num/ 2));
+
+  /* m is the "amplitude" of the sorted pairs. This is a bit tricky to read due
+   * to different indices being used in the paper, unfortunately. */
+  m = inputs_num / 2;
+  while (m > 1)
+  {
+    for (i = 1; (i + (m - 1)) < inputs_num; i += 2)
+    {
+      int left = i;
+      int right = i + (m - 1);
+      sn_comparator_t *c;
+
+      assert (left < right);
+      c = sn_comparator_create (inputs[left], inputs[right]);
+      sn_network_comparator_add (n, c);
+      sn_comparator_destroy (c);
+    }
+
+    m = m / 2;
+  } /* while (m > 1) */
+
+  return (0);
+} /* }}} int sn_network_create_pairwise_internal */
+
+sn_network_t *sn_network_create_pairwise (int inputs_num) /* {{{ */
+{
+  sn_network_t *n = sn_network_create (inputs_num);
+  int inputs[inputs_num];
+  int i;
+
+  if (n == NULL)
+    return (NULL);
+
+  for (i = 0; i < inputs_num; i++)
+    inputs[i] = i;
+  
+  sn_network_create_pairwise_internal (n, inputs, inputs_num);
+  sn_network_compress (n);
+
+  return (n);
+} /* }}} sn_network_t *sn_network_create_pairwise */
+

 int sn_network_stage_add (sn_network_t *n, sn_stage_t *s) /* {{{ */
 {
   sn_stage_t **temp;
 int sn_network_stage_add (sn_network_t *n, sn_stage_t *s) /* {{{ */
 {
   sn_stage_t **temp;

diff --git a/src/sn_network.h b/src/sn_network.h
index d312c35..f56e3ca 100644 (file)
--- a/src/sn_network.h
+++ b/src/sn_network.h
@@ -87,6 +87,15 @@ void sn_network_destroy (sn_network_t *n);
 sn_network_t *sn_network_create_odd_even_mergesort (int inputs_num);
 
 /**
 sn_network_t *sn_network_create_odd_even_mergesort (int inputs_num);
 
 /**

+ * Creates a new sorting network using the Pairwise sorting algorithm published
+ * by Ian Parberry.
+ * \param inputs_num Number of inputs / outputs of the sorting network.
+ * \return A pointer to the newly allocated sorting network or \c NULL if an
+ *   invalid number of inputs was given or allocation failed.
+ */
+sn_network_t *sn_network_create_pairwise (int inputs_num);
+
+/**

  * Append a new stage to a comparator network.
  *
  * \param n The comparator network to which to add the stage.
  * Append a new stage to a comparator network.
  *
  * \param n The comparator network to which to add the stage.