Re: [Help-glpk] How to skip scaling

[Heinrich Schuchardt]

Hello Terry,

the MIP presolver calls scaling. If you disable the presolver no scaling
is done. The MIP presolver is disabled by default.

glp_iocp iocp;
glp_init_iocp(iocp);
// iocp.presolve = GLP_OFF;
glp_intopt(lp, iocp);

cf. doc/glpk.pdf of the source distribution available at
http://ftp.gnu.org/gnu/glpk/glpk-4.57.tar.gz

Best regards

Heinrich Schuchardt

On 18.11.2015 05:36, Terry wrote:
> I'm solving binary MIPs using these basic steps:
> 
> mip = glp_create_prob();
> glp_read_lp(mip, NULL, filename);
> parm.presolve = GLP_ON;
> glp_intopt(mip, &parm);
> status = glp_mip_status(mip);
> 
> For all my MIPs, GLPK always says:
> 
> Problem data seem to be well scaled
>                                                     
> Apparently it tries to scale it, and figures out it's unnecessary. I'm
> solving many similar MIPs and would like it to skip this scaling step.
> 
> I tried this before calling glp_intopt():
> 
> glp_scale_prob(mip, GLP_SF_SKIP);
> 
> But, it still tells me it's well scaled. How can I skip it?
> 
> Thanks,
> Terry
> 
> 
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