title: lpsolve solves the integer linear programming without meeting the given constraints
body: <p>I am wondering whether any one here uses lpsolve to solve linear programming problem.</p>
  
  <p>I have defined a integer linear programming problem in a file where there is a constraint x45=0(there are also other integer variables). After the problem is solved by lpsolve, the result reported strangely is x45=1. However, if I put a label before the constraint, for example, c1:x45=0, then the constraint will be met. Anyone here know what's going on?</p>
  
  <p>So the problem I defined in my LP file is like:</p>
  
  <pre><code>max: 0 x0 262 x1 262 x2 262 x3 262 x4 262 x5 262 x6 262 x7 270 x8 0 x9 270 x10 270 x11 270 x12 270 x13 270 x14 270 x15;
  549 x16 549 x17 0 x18 549 x19 549 x20 549 x21 549 x22 549 x23 &gt;= 1; 
  603 x24 603 x25 603 x26 0 x27 603 x28 603 x29 603 x30 603 x31 &gt;= 1;
  x0=0;
  x9=0;
  x18=0;
  x27=0;
  x36=0;
  x45=0;
  x54=0;
  x63=0;
  x0=x0; x1=x8; x2=x16; x3=x24; x4=x32; x5=x40; x6=x48; x7=x56; x8=x1; x9=x9; x10=x17; x11=x25; x12=x33; x13=x41; x14=x49; x15=x57; x16=x2; x17=x10; x18=x18; x19=x26; x20=x34; x21=x42; x22=x50; x23=x58; x24=x3; x25=x11; x26=x19; x27=x27; x28=x35; x29=x43; x30=x51; x31=x59; x32=x4; x33=x12; x34=x20; x35=x28; x36=x36; x37=x44; x38=x52; x39=x60; x40=x5; x41=x13; x42=x21; x43=x29; x44=x37; x45=x45; x46=x53; x47=x61; x48=x6; x49=x14; x50=x22; x51=x30; x52=x38; x53=x46; x54=x54; x55=x62; x56=x7; x57=x15; x58=x23; x59=x31; x60=x39; x61=x47; x62=x55; x63=x63; x0 x1 x2 x3 x4 x5 x6 x7=1; x8 x9 x10 x11 x12 x13 x14 x15=1; x16 x17 x18 x19 x20 x21 x22 x23=1; x24 x25 x26 x27 x28 x29 x30 x31=1; x32 x33 x34 x35 x36 x37 x38 x39=1; x40 x41 x42 x43 x44 x45 x46 x47=1; x48 x49 x50 x51 x52 x53 x54 x55=1; x56 x57 x58 x59 x60 x61 x62 x63=1;
  
  bin x0,x1,x2,x3,x4,x5,x6,x7,x8,x9,x10,x11,x12,x13,x14,x15,x16,x17,x18,x19,x20,x21,x22,x23,x24,x25,x26,x27,x28,x29,x30,x31,x32,x33,x34,x35,x36,x37,x38,x39,x40,x41,x42,x43,x44,x45,x46,x47,x48,x49,x50,x51,x52,x53,x54,x55,x56,x57,x58,x59,x60,x61,x62,x63;
  </code></pre>
  
  <p>By solving it, the result is:</p>
  
  <pre><code>Value of objective function: 532.00000000
  
  Actual values of the variables:
  x0                              0
  x1                              0
  x2                              0
  x3                              0
  x4                              0
  x5                              0
  x6                              0
  x7                              1
  x8                              0
  x9                              0
  x10                             1
  x11                             0
  x12                             0
  x13                             0
  x14                             0
  x15                             0
  x16                             0
  x17                             1
  x18                             0
  x19                             0
  x20                             0
  x21                             0
  x22                             0
  x23                             0
  x24                             0
  x25                             0
  x26                             0
  x27                             0
  x28                             1
  x29                             0
  x30                             0
  x31                             0
  x36                             0
  x45                             1
  x54                             1
  x63                             0
  x32                             0
  x40                             0
  x48                             0
  x56                             1
  x33                             0
  x41                             0
  x49                             0
  x57                             0
  x34                             0
  x42                             0
  x50                             0
  x58                             0
  x35                             1
  x43                             0
  x51                             0
  x59                             0
  x37                             0
  x44                             0
  x38                             0
  x52                             0
  x39                             0
  x60                             0
  x46                             0
  x53                             0
  x47                             0
  x61                             0
  x55                             0
  x62                             0
  </code></pre>
  
  <p>As you can see. x45 and x54 are both 1 while other constraints are all met. If I put a lable before the constraint such as : </p>
  
  <pre><code>c1: x45=0;
  </code></pre>
  
  <p>Then it will be met. I am not sure why this makes a difference</p>