/* ------------------------------------------------------------------------- * This program simulates a simple (s,S) inventory system using demand read   * from a text file.  Backlogging is permitted and there is no delivery lag. * The output statistics are the average demand and order per time interval * (they should be equal), the relative frequency of setup and the time * averaged held (+) and short (-) inventory levels. * * NOTE: use 0 <= MINIMUM < MAXIMUM, i.e., 0 <= s < S. * * Name              : sis1.c  (Simple Inventory System, version 1) * Authors           : Steve Park & Dave Geyer  * Language          : ANSI C  * Latest Revision   : 8-20-97  * Compile with      : gcc sis1.c * ------------------------------------------------------------------------- */#include <stdio.h>                        #define FILENAME  "sis1.dat"            /* input data file                */#define MINIMUM   20                    /* 's' inventory policy parameter */#define MAXIMUM   80                    /* 'S' inventory policy parameter */#define sqr(x)    ((x) * (x))/* ======================== */   long GetDemand(FILE *fp)            /* ======================== */{  long d;  fscanf(fp, "%ld\n", &d);  return (d);}/* ============== */   int main(void)/* ============== */{  FILE *fp;                                /* input data file         */  long index     = 0;                      /* time interval index     */  long inventory = MAXIMUM;                /* current inventory level */  long demand;                             /* amount of demand        */  long order;                              /* amount of order         */  struct {                                 /* sum of ...              */    double setup;                          /*   setup instances       */    double holding;                        /*   inventory held (+)    */    double shortage;                       /*   inventory short (-)   */    double order;                          /*   orders                */    double demand;                         /*   demands               */  } sum = { 0.0, 0.0, 0.0, 0.0, 0.0 };  fp = fopen(FILENAME, "r");  if (fp == NULL) {    fprintf(stderr, "Cannot open input file %s\n", FILENAME);    return (1);  }  while (!feof(fp)) {    index++;    if (inventory < MINIMUM) {             /* place an order          */      order         = MAXIMUM - inventory;      sum.setup++;      sum.order    += order;    }    else                                   /* no order                 */      order         = 0;                       inventory      += order;               /* there is no delivery lag */    demand          = GetDemand(fp);    sum.demand     += demand;    if (inventory > demand)       sum.holding  += (inventory - 0.5 * demand);    else {      sum.holding  += sqr(inventory) / (2.0 * demand);      sum.shortage += sqr(demand - inventory) / (2.0 * demand);    }    inventory      -= demand;  }  if (inventory < MAXIMUM) {               /* force the final inventory to */    order           = MAXIMUM - inventory; /* match the initial inventory  */    sum.setup++;    sum.order      += order;    inventory      += order;  }  printf("\nfor %ld time intervals ", index);  printf("with an average demand of %6.2f\n", sum.demand / index);  printf("and policy parameters (s, S) = (%d, %d)\n\n", MINIMUM, MAXIMUM);  printf("   average order ............ = %6.2f\n", sum.order / index);  printf("   setup frequency .......... = %6.2f\n", sum.setup / index);  printf("   average holding level .... = %6.2f\n", sum.holding / index);  printf("   average shortage level ... = %6.2f\n", sum.shortage / index);  fclose(fp);  return (0);}