how to use the C api "GRBsetlogcallbackfuncenv" correctly

回答済み

ZHANG Qi

2025年12月13日 18:16 編集済み

• 
• 

I try to use the api like:

I expect that “Hello World” and other solving process messages are sent to “callback”, but actually, the callback isn't called at all. Nothing is shown in the console. Did I misunderstand how this api works?

What I exactly want to do is redirect the Gurobi logging to another stream.

Gurobi version: 11.0.0

system: win11

complier: msvc

関連

• C
• Callbacks

0

• 

  Riley Clement

  • Gurobi Staff

  2025年12月15日 02:07

  Hi Qi,

  When I compile and run the following code (with v11 Gurobi):

  #include "gurobi_c.h"
  
  int callback(char *msg, void *logdata) {
      fprintf(stderr, "Callback: %s\n", msg);
      fflush(stderr);
      return 0;
  }
  
  int main() {
      int error = 0;
      GRBenv *env = NULL;
      GRBmodel *model = NULL;
  
      error = GRBemptyenv(&env);
      if (error) goto QUIT;
  
      error = GRBsetstrparam(env, "LogFile", "mip1.log");
      if (error) goto QUIT;
  
      error = GRBstartenv(env);
      if (error) goto QUIT;
  
      error = GRBsetlogcallbackfuncenv(env, callback, NULL);
      if (error) goto QUIT;
  
      GRBmsg(env, "---------------- Hello World ---------------- \n");
      
      error = GRBsetlogcallbackfuncenv(env, NULL, NULL);
      if (error) goto QUIT;
  
  QUIT:
      if (error) {
          printf( "ERROR: %s\n", GRBgeterrormsg(env));
          return 1;
      }
      GRBfreeenv(env);
      return 0;
  }

  I get the following output to console:

  Set parameter LicenseID to value xxxxxx
  Set parameter LogFile to value "mip1.log"
  ---------------- Hello World ---------------- 
  Callback: ---------------- Hello World ---------------- 

  You don't see similar output?

  - Riley

  0
• 

  ZHANG Qi

  2025年12月16日 05:30

  • 
  • 

  Thanks!
  Only when I add a ‘\n’ at the end of the string passed to GRBmsg, I can see the same output.

  0
• 

  Riley Clement

  • Gurobi Staff

  2025年12月16日 06:25

  Ok, is your problem now solved then?  Or is there still an issue?

  Don't forget you will also need to use GRBsetlogcallbackfunc in a similar way so you can redirect output from the model.

  0
• 

  ZHANG Qi

  2025年12月16日 15:51

  • 
  • 

  yes,  after i add a ‘\n’, no problem anymore. Thanks again!

  0

サインインしてコメントを残してください。