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/* rdmaxf.c (read maximum flow problem data in DIMACS format) */
/***********************************************************************
* This code is part of GLPK (GNU Linear Programming Kit).
*
* Copyright (C) 2009-2016 Andrew Makhorin, Department for Applied
* Informatics, Moscow Aviation Institute, Moscow, Russia. All rights
* reserved. E-mail: <mao@gnu.org>.
*
* GLPK 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, either version 3 of the License, or
* (at your option) any later version.
*
* GLPK 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 GLPK. If not, see <http://www.gnu.org/licenses/>.
***********************************************************************/
#include "dimacs.h"
#include "glpk.h"
#include "misc.h"
#define error dmx_error
#define warning dmx_warning
#define read_char dmx_read_char
#define read_designator dmx_read_designator
#define read_field dmx_read_field
#define end_of_line dmx_end_of_line
#define check_int dmx_check_int
/***********************************************************************
* NAME
*
* glp_read_maxflow - read maximum flow problem data in DIMACS format
*
* SYNOPSIS
*
* int glp_read_maxflow(glp_graph *G, int *s, int *t, int a_cap,
* const char *fname);
*
* DESCRIPTION
*
* The routine glp_read_maxflow reads maximum flow problem data in
* DIMACS format from a text file.
*
* RETURNS
*
* If the operation was successful, the routine returns zero. Otherwise
* it prints an error message and returns non-zero. */
int glp_read_maxflow(glp_graph *G, int *_s, int *_t, int a_cap,
const char *fname)
{ DMX _csa, *csa = &_csa;
glp_arc *a;
int i, j, k, s, t, nv, na, ret = 0;
double cap;
if (a_cap >= 0 && a_cap > G->a_size - (int)sizeof(double))
xerror("glp_read_maxflow: a_cap = %d; invalid offset\n",
a_cap);
glp_erase_graph(G, G->v_size, G->a_size);
if (setjmp(csa->jump))
{ ret = 1;
goto done;
}
csa->fname = fname;
csa->fp = NULL;
csa->count = 0;
csa->c = '\n';
csa->field[0] = '\0';
csa->empty = csa->nonint = 0;
xprintf("Reading maximum flow problem data from '%s'...\n",
fname);
csa->fp = glp_open(fname, "r");
if (csa->fp == NULL)
{ xprintf("Unable to open '%s' - %s\n", fname, get_err_msg());
longjmp(csa->jump, 1);
}
/* read problem line */
read_designator(csa);
if (strcmp(csa->field, "p") != 0)
error(csa, "problem line missing or invalid");
read_field(csa);
if (strcmp(csa->field, "max") != 0)
error(csa, "wrong problem designator; 'max' expected");
read_field(csa);
if (!(str2int(csa->field, &nv) == 0 && nv >= 2))
error(csa, "number of nodes missing or invalid");
read_field(csa);
if (!(str2int(csa->field, &na) == 0 && na >= 0))
error(csa, "number of arcs missing or invalid");
xprintf("Flow network has %d node%s and %d arc%s\n",
nv, nv == 1 ? "" : "s", na, na == 1 ? "" : "s");
if (nv > 0) glp_add_vertices(G, nv);
end_of_line(csa);
/* read node descriptor lines */
s = t = 0;
for (;;)
{ read_designator(csa);
if (strcmp(csa->field, "n") != 0) break;
read_field(csa);
if (str2int(csa->field, &i) != 0)
error(csa, "node number missing or invalid");
if (!(1 <= i && i <= nv))
error(csa, "node number %d out of range", i);
read_field(csa);
if (strcmp(csa->field, "s") == 0)
{ if (s > 0)
error(csa, "only one source node allowed");
s = i;
}
else if (strcmp(csa->field, "t") == 0)
{ if (t > 0)
error(csa, "only one sink node allowed");
t = i;
}
else
error(csa, "wrong node designator; 's' or 't' expected");
if (s > 0 && s == t)
error(csa, "source and sink nodes must be distinct");
end_of_line(csa);
}
if (s == 0)
error(csa, "source node descriptor missing\n");
if (t == 0)
error(csa, "sink node descriptor missing\n");
if (_s != NULL) *_s = s;
if (_t != NULL) *_t = t;
/* read arc descriptor lines */
for (k = 1; k <= na; k++)
{ if (k > 1) read_designator(csa);
if (strcmp(csa->field, "a") != 0)
error(csa, "wrong line designator; 'a' expected");
read_field(csa);
if (str2int(csa->field, &i) != 0)
error(csa, "starting node number missing or invalid");
if (!(1 <= i && i <= nv))
error(csa, "starting node number %d out of range", i);
read_field(csa);
if (str2int(csa->field, &j) != 0)
error(csa, "ending node number missing or invalid");
if (!(1 <= j && j <= nv))
error(csa, "ending node number %d out of range", j);
read_field(csa);
if (!(str2num(csa->field, &cap) == 0 && cap >= 0.0))
error(csa, "arc capacity missing or invalid");
check_int(csa, cap);
a = glp_add_arc(G, i, j);
if (a_cap >= 0)
memcpy((char *)a->data + a_cap, &cap, sizeof(double));
end_of_line(csa);
}
xprintf("%d lines were read\n", csa->count);
done: if (ret) glp_erase_graph(G, G->v_size, G->a_size);
if (csa->fp != NULL) glp_close(csa->fp);
return ret;
}
/* eof */
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