github.com/razvanm/vanadium-go-1.3@v0.0.0-20160721203343-4a65068e5915/test/bench/shootout/fannkuch.c (about)

     1  /*
     2  Redistribution and use in source and binary forms, with or without
     3  modification, are permitted provided that the following conditions are met:
     4  
     5      * Redistributions of source code must retain the above copyright
     6      notice, this list of conditions and the following disclaimer.
     7  
     8      * Redistributions in binary form must reproduce the above copyright
     9      notice, this list of conditions and the following disclaimer in the
    10      documentation and/or other materials provided with the distribution.
    11  
    12      * Neither the name of "The Computer Language Benchmarks Game" nor the
    13      name of "The Computer Language Shootout Benchmarks" nor the names of
    14      its contributors may be used to endorse or promote products derived
    15      from this software without specific prior written permission.
    16  
    17  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
    18  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
    19  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
    20  ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
    21  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
    22  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
    23  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
    24  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
    25  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
    26  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
    27  POSSIBILITY OF SUCH DAMAGE.
    28  */
    29  
    30  /*
    31   * The Computer Language Shootout
    32   * http://shootout.alioth.debian.org/
    33   * Contributed by Heiner Marxen
    34   *
    35   * "fannkuch"	for C gcc
    36   *
    37   * $Id: fannkuch.1.gcc.code,v 1.15 2009-04-28 15:39:31 igouy-guest Exp $
    38   */
    39  
    40  #include <stdio.h>
    41  #include <stdlib.h>
    42  
    43  #define Int	int
    44  #define Aint	int
    45  
    46      static long
    47  fannkuch( int n )
    48  {
    49      Aint*	perm;
    50      Aint*	perm1;
    51      Aint*	count;
    52      long	flips;
    53      long	flipsMax;
    54      Int		r;
    55      Int		i;
    56      Int		k;
    57      Int		didpr;
    58      const Int	n1	= n - 1;
    59  
    60      if( n < 1 ) return 0;
    61  
    62      perm  = calloc(n, sizeof(*perm ));
    63      perm1 = calloc(n, sizeof(*perm1));
    64      count = calloc(n, sizeof(*count));
    65  
    66      for( i=0 ; i<n ; ++i ) perm1[i] = i;	/* initial (trivial) permu */
    67  
    68      r = n; didpr = 0; flipsMax = 0;
    69      for(;;) {
    70  	if( didpr < 30 ) {
    71  	    for( i=0 ; i<n ; ++i ) printf("%d", (int)(1+perm1[i]));
    72  	    printf("\n");
    73  	    ++didpr;
    74  	}
    75  	for( ; r!=1 ; --r ) {
    76  	    count[r-1] = r;
    77  	}
    78  
    79  #define XCH(x,y)	{ Aint t_mp; t_mp=(x); (x)=(y); (y)=t_mp; }
    80  
    81  	if( ! (perm1[0]==0 || perm1[n1]==n1) ) {
    82  	    flips = 0;
    83  	    for( i=1 ; i<n ; ++i ) {	/* perm = perm1 */
    84  		perm[i] = perm1[i];
    85  	    }
    86  	    k = perm1[0];		/* cache perm[0] in k */
    87  	    do {			/* k!=0 ==> k>0 */
    88  		Int	j;
    89  		for( i=1, j=k-1 ; i<j ; ++i, --j ) {
    90  		    XCH(perm[i], perm[j])
    91  		}
    92  		++flips;
    93  		/*
    94  		 * Now exchange k (caching perm[0]) and perm[k]... with care!
    95  		 * XCH(k, perm[k]) does NOT work!
    96  		 */
    97  		j=perm[k]; perm[k]=k ; k=j;
    98  	    }while( k );
    99  	    if( flipsMax < flips ) {
   100  		flipsMax = flips;
   101  	    }
   102  	}
   103  
   104  	for(;;) {
   105  	    if( r == n ) {
   106  		return flipsMax;
   107  	    }
   108  	    /* rotate down perm[0..r] by one */
   109  	    {
   110  		Int	perm0 = perm1[0];
   111  		i = 0;
   112  		while( i < r ) {
   113  		    k = i+1;
   114  		    perm1[i] = perm1[k];
   115  		    i = k;
   116  		}
   117  		perm1[r] = perm0;
   118  	    }
   119  	    if( (count[r] -= 1) > 0 ) {
   120  		break;
   121  	    }
   122  	    ++r;
   123  	}
   124      }
   125  }
   126  
   127      int
   128  main( int argc, char* argv[] )
   129  {
   130      int		n = (argc>1) ? atoi(argv[1]) : 0;
   131  
   132      printf("Pfannkuchen(%d) = %ld\n", n, fannkuch(n));
   133      return 0;
   134  }