lemon-project-template-glpk

annotate deps/glpk/doc/glpk01.tex @ 11:4fc6ad2fb8a6

Test GLPK in src/main.cc
author Alpar Juttner <alpar@cs.elte.hu>
date Sun, 06 Nov 2011 21:43:29 +0100
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alpar@9 1 %* glpk01.tex *%
alpar@9 2
alpar@9 3 \chapter{Introduction}
alpar@9 4
alpar@9 5 GLPK (\underline{G}NU \underline{L}inear \underline{P}rogramming
alpar@9 6 \underline{K}it) is a set of routines written in the ANSI C programming
alpar@9 7 language and organized in the form of a callable library. It is intended
alpar@9 8 for solving linear programming (LP), mixed integer programming (MIP),
alpar@9 9 and other related problems.
alpar@9 10
alpar@9 11 \section{LP problem}
alpar@9 12 \label{seclp}
alpar@9 13
alpar@9 14 GLPK assumes the following formulation of {\it linear programming (LP)}
alpar@9 15 problem:
alpar@9 16
alpar@9 17 \medskip
alpar@9 18
alpar@9 19 \noindent
alpar@9 20 \hspace{.5in} minimize (or maximize)
alpar@9 21 $$z = c_1x_{m+1} + c_2x_{m+2} + \dots + c_nx_{m+n} + c_0 \eqno (1.1)$$
alpar@9 22 \hspace{.5in} subject to linear constraints
alpar@9 23 $$
alpar@9 24 \begin{array}{r@{\:}c@{\:}r@{\:}c@{\:}r@{\:}c@{\:}r}
alpar@9 25 x_1&=&a_{11}x_{m+1}&+&a_{12}x_{m+2}&+ \dots +&a_{1n}x_{m+n} \\
alpar@9 26 x_2&=&a_{21}x_{m+1}&+&a_{22}x_{m+2}&+ \dots +&a_{2n}x_{m+n} \\
alpar@9 27 \multicolumn{7}{c}
alpar@9 28 {.\ \ .\ \ .\ \ .\ \ .\ \ .\ \ .\ \ .\ \ .\ \ .\ \ .\ \ .\ \ .\ \ .} \\
alpar@9 29 x_m&=&a_{m1}x_{m+1}&+&a_{m2}x_{m+2}&+ \dots +&a_{mn}x_{m+n} \\
alpar@9 30 \end{array} \eqno (1.2)
alpar@9 31 $$
alpar@9 32 \hspace{.5in} and bounds of variables
alpar@9 33 $$
alpar@9 34 \begin{array}{r@{\:}c@{\:}c@{\:}c@{\:}l}
alpar@9 35 l_1&\leq&x_1&\leq&u_1 \\
alpar@9 36 l_2&\leq&x_2&\leq&u_2 \\
alpar@9 37 \multicolumn{5}{c}{.\ \ .\ \ .\ \ .\ \ .}\\
alpar@9 38 l_{m+n}&\leq&x_{m+n}&\leq&u_{m+n} \\
alpar@9 39 \end{array} \eqno (1.3)
alpar@9 40 $$
alpar@9 41 where: $x_1, x_2, \dots, x_m$ are auxiliary variables;
alpar@9 42 $x_{m+1}, x_{m+2}, \dots, x_{m+n}$ are\linebreak structural variables;
alpar@9 43 $z$ is the objective function;
alpar@9 44 $c_1, c_2, \dots, c_n$ are objective coefficients;
alpar@9 45 $c_0$ is the constant term (``shift'') of the objective function;
alpar@9 46 $a_{11}, a_{12}, \dots, a_{mn}$ are constraint coefficients;
alpar@9 47 $l_1, l_2, \dots, l_{m+n}$ are lower bounds of variables;
alpar@9 48 $u_1, u_2, \dots, u_{m+n}$ are upper bounds of variables.
alpar@9 49
alpar@9 50 Auxiliary variables are also called {\it rows}, because they correspond
alpar@9 51 to rows of the constraint matrix (i.e. a matrix built of the constraint
alpar@9 52 coefficients). Similarly, structural variables are also called
alpar@9 53 {\it columns}, because they correspond to columns of the constraint
alpar@9 54 matrix.
alpar@9 55
alpar@9 56 Bounds of variables can be finite as well as infinite. Besides, lower
alpar@9 57 and upper bounds can be equal to each other. Thus, the following types
alpar@9 58 of variables are possible:
alpar@9 59 \begin{center}
alpar@9 60 \begin{tabular}{r@{}c@{}ll}
alpar@9 61 \multicolumn{3}{c}{Bounds of variable} & Type of variable \\
alpar@9 62 \hline
alpar@9 63 $-\infty <$ &$\ x_k\ $& $< +\infty$ & Free (unbounded) variable \\
alpar@9 64 $l_k \leq$ &$\ x_k\ $& $< +\infty$ & Variable with lower bound \\
alpar@9 65 $-\infty <$ &$\ x_k\ $& $\leq u_k$ & Variable with upper bound \\
alpar@9 66 $l_k \leq$ &$\ x_k\ $& $\leq u_k$ & Double-bounded variable \\
alpar@9 67 $l_k =$ &$\ x_k\ $& $= u_k$ & Fixed variable \\
alpar@9 68 \end{tabular}
alpar@9 69 \end{center}
alpar@9 70 \noindent
alpar@9 71 Note that the types of variables shown above are applicable to
alpar@9 72 structural as well as to auxiliary variables.
alpar@9 73
alpar@9 74 To solve the LP problem (1.1)---(1.3) is to find such values of all
alpar@9 75 structural and auxiliary variables, which:
alpar@9 76
alpar@9 77 $\bullet$ satisfy to all the linear constraints (1.2), and
alpar@9 78
alpar@9 79 $\bullet$ are within their bounds (1.3), and
alpar@9 80
alpar@9 81 $\bullet$ provide the smallest (in case of minimization) or the largest
alpar@9 82 (in case of maximization) value of the objective function (1.1).
alpar@9 83
alpar@9 84 \section{MIP problem}
alpar@9 85
alpar@9 86 {\it Mixed integer linear programming (MIP)} problem is LP problem in
alpar@9 87 which some variables are additionally required to be integer.
alpar@9 88
alpar@9 89 GLPK assumes that MIP problem has the same formulation as ordinary
alpar@9 90 (pure) LP problem (1.1)---(1.3), i.e. includes auxiliary and structural
alpar@9 91 variables, which may have lower and/or upper bounds. However, in case of
alpar@9 92 MIP problem some variables may be required to be integer. This
alpar@9 93 additional constraint means that a value of each {\it integer variable}
alpar@9 94 must be only integer number. (Should note that GLPK allows only
alpar@9 95 structural variables to be of integer kind.)
alpar@9 96
alpar@9 97 \section{Using the package}
alpar@9 98
alpar@9 99 \subsection{Brief example}
alpar@9 100
alpar@9 101 In order to understand what GLPK is from the user's standpoint,
alpar@9 102 consider the following simple LP problem:
alpar@9 103
alpar@9 104 \medskip
alpar@9 105
alpar@9 106 \noindent
alpar@9 107 \hspace{.5in} maximize
alpar@9 108 $$z = 10 x_1 + 6 x_2 + 4 x_3$$
alpar@9 109 \hspace{.5in} subject to
alpar@9 110 $$
alpar@9 111 \begin{array}{r@{\:}c@{\:}r@{\:}c@{\:}r@{\:}c@{\:}r}
alpar@9 112 x_1 &+&x_2 &+&x_3 &\leq 100 \\
alpar@9 113 10 x_1 &+& 4 x_2 & +&5 x_3 & \leq 600 \\
alpar@9 114 2 x_1 &+& 2 x_2 & +& 6 x_3 & \leq 300 \\
alpar@9 115 \end{array}
alpar@9 116 $$
alpar@9 117 \hspace{.5in} where all variables are non-negative
alpar@9 118 $$x_1 \geq 0, \ x_2 \geq 0, \ x_3 \geq 0$$
alpar@9 119
alpar@9 120 At first this LP problem should be transformed to the standard form
alpar@9 121 (1.1)---(1.3). This can be easily done by introducing auxiliary
alpar@9 122 variables, by one for each original inequality constraint. Thus, the
alpar@9 123 problem can be reformulated as follows:
alpar@9 124
alpar@9 125 \medskip
alpar@9 126
alpar@9 127 \noindent
alpar@9 128 \hspace{.5in} maximize
alpar@9 129 $$z = 10 x_1 + 6 x_2 + 4 x_3$$
alpar@9 130 \hspace{.5in} subject to
alpar@9 131 $$
alpar@9 132 \begin{array}{r@{\:}c@{\:}r@{\:}c@{\:}r@{\:}c@{\:}r}
alpar@9 133 p& = &x_1 &+&x_2 &+&x_3 \\
alpar@9 134 q& = &10 x_1 &+& 4 x_2 &+& 5 x_3 \\
alpar@9 135 r& = &2 x_1 &+& 2 x_2 &+& 6 x_3 \\
alpar@9 136 \end{array}
alpar@9 137 $$
alpar@9 138 \hspace{.5in} and bounds of variables
alpar@9 139 $$
alpar@9 140 \begin{array}{ccc}
alpar@9 141 \nonumber -\infty < p \leq 100 && 0 \leq x_1 < +\infty \\
alpar@9 142 \nonumber -\infty < q \leq 600 && 0 \leq x_2 < +\infty \\
alpar@9 143 \nonumber -\infty < r \leq 300 && 0 \leq x_3 < +\infty \\
alpar@9 144 \end{array}
alpar@9 145 $$
alpar@9 146 where $p, q, r$ are auxiliary variables (rows), and $x_1, x_2, x_3$ are
alpar@9 147 structural variables (columns).
alpar@9 148
alpar@9 149 The example C program shown below uses GLPK API routines in order to
alpar@9 150 solve this LP problem.\footnote{If you just need to solve LP or MIP
alpar@9 151 instance, you may write it in MPS or CPLEX LP format and then use the
alpar@9 152 GLPK stand-alone solver to obtain a solution. This is much less
alpar@9 153 time-consuming than programming in C with GLPK API routines.}
alpar@9 154
alpar@9 155 \newpage
alpar@9 156
alpar@9 157 \begin{verbatim}
alpar@9 158 /* sample.c */
alpar@9 159
alpar@9 160 #include <stdio.h>
alpar@9 161 #include <stdlib.h>
alpar@9 162 #include <glpk.h>
alpar@9 163
alpar@9 164 int main(void)
alpar@9 165 { glp_prob *lp;
alpar@9 166 int ia[1+1000], ja[1+1000];
alpar@9 167 double ar[1+1000], z, x1, x2, x3;
alpar@9 168 s1: lp = glp_create_prob();
alpar@9 169 s2: glp_set_prob_name(lp, "sample");
alpar@9 170 s3: glp_set_obj_dir(lp, GLP_MAX);
alpar@9 171 s4: glp_add_rows(lp, 3);
alpar@9 172 s5: glp_set_row_name(lp, 1, "p");
alpar@9 173 s6: glp_set_row_bnds(lp, 1, GLP_UP, 0.0, 100.0);
alpar@9 174 s7: glp_set_row_name(lp, 2, "q");
alpar@9 175 s8: glp_set_row_bnds(lp, 2, GLP_UP, 0.0, 600.0);
alpar@9 176 s9: glp_set_row_name(lp, 3, "r");
alpar@9 177 s10: glp_set_row_bnds(lp, 3, GLP_UP, 0.0, 300.0);
alpar@9 178 s11: glp_add_cols(lp, 3);
alpar@9 179 s12: glp_set_col_name(lp, 1, "x1");
alpar@9 180 s13: glp_set_col_bnds(lp, 1, GLP_LO, 0.0, 0.0);
alpar@9 181 s14: glp_set_obj_coef(lp, 1, 10.0);
alpar@9 182 s15: glp_set_col_name(lp, 2, "x2");
alpar@9 183 s16: glp_set_col_bnds(lp, 2, GLP_LO, 0.0, 0.0);
alpar@9 184 s17: glp_set_obj_coef(lp, 2, 6.0);
alpar@9 185 s18: glp_set_col_name(lp, 3, "x3");
alpar@9 186 s19: glp_set_col_bnds(lp, 3, GLP_LO, 0.0, 0.0);
alpar@9 187 s20: glp_set_obj_coef(lp, 3, 4.0);
alpar@9 188 s21: ia[1] = 1, ja[1] = 1, ar[1] = 1.0; /* a[1,1] = 1 */
alpar@9 189 s22: ia[2] = 1, ja[2] = 2, ar[2] = 1.0; /* a[1,2] = 1 */
alpar@9 190 s23: ia[3] = 1, ja[3] = 3, ar[3] = 1.0; /* a[1,3] = 1 */
alpar@9 191 s24: ia[4] = 2, ja[4] = 1, ar[4] = 10.0; /* a[2,1] = 10 */
alpar@9 192 s25: ia[5] = 3, ja[5] = 1, ar[5] = 2.0; /* a[3,1] = 2 */
alpar@9 193 s26: ia[6] = 2, ja[6] = 2, ar[6] = 4.0; /* a[2,2] = 4 */
alpar@9 194 s27: ia[7] = 3, ja[7] = 2, ar[7] = 2.0; /* a[3,2] = 2 */
alpar@9 195 s28: ia[8] = 2, ja[8] = 3, ar[8] = 5.0; /* a[2,3] = 5 */
alpar@9 196 s29: ia[9] = 3, ja[9] = 3, ar[9] = 6.0; /* a[3,3] = 6 */
alpar@9 197 s30: glp_load_matrix(lp, 9, ia, ja, ar);
alpar@9 198 s31: glp_simplex(lp, NULL);
alpar@9 199 s32: z = glp_get_obj_val(lp);
alpar@9 200 s33: x1 = glp_get_col_prim(lp, 1);
alpar@9 201 s34: x2 = glp_get_col_prim(lp, 2);
alpar@9 202 s35: x3 = glp_get_col_prim(lp, 3);
alpar@9 203 s36: printf("\nz = %g; x1 = %g; x2 = %g; x3 = %g\n",
alpar@9 204 z, x1, x2, x3);
alpar@9 205 s37: glp_delete_prob(lp);
alpar@9 206 return 0;
alpar@9 207 }
alpar@9 208
alpar@9 209 /* eof */
alpar@9 210 \end{verbatim}
alpar@9 211
alpar@9 212 The statement \verb|s1| creates a problem object. Being created the
alpar@9 213 object is initially empty. The statement \verb|s2| assigns a symbolic
alpar@9 214 name to the problem object.
alpar@9 215
alpar@9 216 The statement \verb|s3| calls the routine \verb|glp_set_obj_dir| in
alpar@9 217 order to set the optimization direction flag, where \verb|GLP_MAX| means
alpar@9 218 maximization.
alpar@9 219
alpar@9 220 The statement \verb|s4| adds three rows to the problem object.
alpar@9 221
alpar@9 222 The statement \verb|s5| assigns the symbolic name `\verb|p|' to the
alpar@9 223 first row, and the statement \verb|s6| sets the type and bounds of the
alpar@9 224 first row, where \verb|GLP_UP| means that the row has an upper bound.
alpar@9 225 The statements \verb|s7|, \verb|s8|, \verb|s9|, \verb|s10| are used in
alpar@9 226 the same way in order to assign the symbolic names `\verb|q|' and
alpar@9 227 `\verb|r|' to the second and third rows and set their types and bounds.
alpar@9 228
alpar@9 229 The statement \verb|s11| adds three columns to the problem object.
alpar@9 230
alpar@9 231 The statement \verb|s12| assigns the symbolic name `\verb|x1|' to the
alpar@9 232 first column, the statement \verb|s13| sets the type and bounds of the
alpar@9 233 first column, where \verb|GLP_LO| means that the column has an lower
alpar@9 234 bound, and the statement \verb|s14| sets the objective coefficient for
alpar@9 235 the first column. The statements \verb|s15|---\verb|s20| are used in the
alpar@9 236 same way in order to assign the symbolic names `\verb|x2|' and
alpar@9 237 `\verb|x3|' to the second and third columns and set their types, bounds,
alpar@9 238 and objective coefficients.
alpar@9 239
alpar@9 240 The statements \verb|s21|---\verb|s29| prepare non-zero elements of the
alpar@9 241 constraint matrix (i.e. constraint coefficients). Row indices of each
alpar@9 242 element are stored in the array \verb|ia|, column indices are stored in
alpar@9 243 the array \verb|ja|, and numerical values of corresponding elements are
alpar@9 244 stored in the array \verb|ar|. Then the statement \verb|s30| calls
alpar@9 245 the routine \verb|glp_load_matrix|, which loads information from these
alpar@9 246 three arrays into the problem object.
alpar@9 247
alpar@9 248 Now all data have been entered into the problem object, and therefore
alpar@9 249 the statement \verb|s31| calls the routine \verb|glp_simplex|, which is
alpar@9 250 a driver to the simplex method, in order to solve the LP problem. This
alpar@9 251 routine finds an optimal solution and stores all relevant information
alpar@9 252 back into the problem object.
alpar@9 253
alpar@9 254 The statement \verb|s32| obtains a computed value of the objective
alpar@9 255 function, and the statements \verb|s33|---\verb|s35| obtain computed
alpar@9 256 values of structural variables (columns), which correspond to the
alpar@9 257 optimal basic solution found by the solver.
alpar@9 258
alpar@9 259 The statement \verb|s36| writes the optimal solution to the standard
alpar@9 260 output. The printout may look like follows:
alpar@9 261
alpar@9 262 {\footnotesize
alpar@9 263 \begin{verbatim}
alpar@9 264 * 0: objval = 0.000000000e+00 infeas = 0.000000000e+00 (0)
alpar@9 265 * 2: objval = 7.333333333e+02 infeas = 0.000000000e+00 (0)
alpar@9 266 OPTIMAL SOLUTION FOUND
alpar@9 267
alpar@9 268 z = 733.333; x1 = 33.3333; x2 = 66.6667; x3 = 0
alpar@9 269 \end{verbatim}
alpar@9 270
alpar@9 271 }
alpar@9 272
alpar@9 273 Finally, the statement \verb|s37| calls the routine
alpar@9 274 \verb|glp_delete_prob|, which frees all the memory allocated to the
alpar@9 275 problem object.
alpar@9 276
alpar@9 277 \subsection{Compiling}
alpar@9 278
alpar@9 279 The GLPK package has the only header file \verb|glpk.h|, which should
alpar@9 280 be available on compiling a C (or C++) program using GLPK API routines.
alpar@9 281
alpar@9 282 If the header file is installed in the default location
alpar@9 283 \verb|/usr/local/include|, the following typical command may be used to
alpar@9 284 compile, say, the example C program described above with the GNU C
alpar@9 285 compiler:
alpar@9 286
alpar@9 287 \begin{verbatim}
alpar@9 288 $ gcc -c sample.c
alpar@9 289 \end{verbatim}
alpar@9 290
alpar@9 291 If \verb|glpk.h| is not in the default location, the corresponding
alpar@9 292 directory containing it should be made known to the C compiler through
alpar@9 293 \verb|-I| option, for example:
alpar@9 294
alpar@9 295 \begin{verbatim}
alpar@9 296 $ gcc -I/foo/bar/glpk-4.15/include -c sample.c
alpar@9 297 \end{verbatim}
alpar@9 298
alpar@9 299 In any case the compilation results in an object file \verb|sample.o|.
alpar@9 300
alpar@9 301 \subsection{Linking}
alpar@9 302
alpar@9 303 The GLPK library is a single file \verb|libglpk.a|. (On systems which
alpar@9 304 support shared libraries there may be also a shared version of the
alpar@9 305 library \verb|libglpk.so|.)
alpar@9 306
alpar@9 307 If the library is installed in the default
alpar@9 308 location \verb|/usr/local/lib|, the following typical command may be
alpar@9 309 used to link, say, the example C program described above against with
alpar@9 310 the library:
alpar@9 311
alpar@9 312 \begin{verbatim}
alpar@9 313 $ gcc sample.o -lglpk -lm
alpar@9 314 \end{verbatim}
alpar@9 315
alpar@9 316 If the GLPK library is not in the default location, the corresponding
alpar@9 317 directory containing it should be made known to the linker through
alpar@9 318 \verb|-L| option, for example:
alpar@9 319
alpar@9 320 \begin{verbatim}
alpar@9 321 $ gcc -L/foo/bar/glpk-4.15 sample.o -lglpk -lm
alpar@9 322 \end{verbatim}
alpar@9 323
alpar@9 324 Depending on configuration of the package linking against with the GLPK
alpar@9 325 library may require the following optional libraries:
alpar@9 326
alpar@9 327 \bigskip
alpar@9 328
alpar@9 329 \begin{tabular}{@{}ll}
alpar@9 330 \verb|-lgmp| & the GNU MP bignum library; \\
alpar@9 331 \verb|-lz| & the zlib data compression library; \\
alpar@9 332 \verb|-lltdl| & the GNU ltdl shared support library. \\
alpar@9 333 \end{tabular}
alpar@9 334
alpar@9 335 \bigskip
alpar@9 336
alpar@9 337 \noindent
alpar@9 338 in which case corresponding libraries should be also made known to the
alpar@9 339 linker, for example:
alpar@9 340
alpar@9 341 \begin{verbatim}
alpar@9 342 $ gcc sample.o -lglpk -lz -lltdl -lm
alpar@9 343 \end{verbatim}
alpar@9 344
alpar@9 345 For more details about configuration options of the GLPK package see
alpar@9 346 Appendix \ref{install}, page \pageref{install}.
alpar@9 347
alpar@9 348 %* eof *%