What does it mean when the parameter XPRS_MIPINFEAS takes the value -1?

Thank you Daniel,

I am calling this function from cb_preintsol, which, in its turn, is in tree_cut_gen.

In principle I want to understand if cb_preintsol is triggered every time that an integer solution is found. (I have the impression that sometimes "cb_node" identifies that the current solution is integer, but then cb_preintsol is not triggered; and vice-versa).

This is why in cb_preintsol I start recovering the LP solution and check myself if its binary variables take integer values. After this is when I see the -1 value for the XPRS_MIPINFEAS parameter with the statement

writeln('is_int is ... ', is_int, ' parameter XPRS_MIPINFEAS is ...', getparam("XPRS_MIPINFEAS")

I am adding the beginning of the code of my cb_preintsol procedure (until the write statement), as well as the tree_cut_gen procedure.

Thanks again,

Elena

procedure cb_preintsol(isheur:boolean, cutoff:real)

declarations

my_tipo: integer

my_corte: linctr

my_corteid: integer

que_index: integer

end-declarations 

writeln("ENTERS preintsol, node: ", getparam("XPRS_nodes"), "ncortes: ", ncorte)

ncorte:=0

returned:=false

is_int:=true

forall(i in N1) bary(i):=getsol(y(i))

forall(i,k,r in N1)barz(i,k,r):=getsol(z(i,k,r))

forall(i in N1| bary(i)>eps) do

if(1-bary(i)>eps) then

is_int:=false

writeln(' y fraccional: i=', i, ' bary(i)=', bary(i))

break

else

forall(k,r in N1|barz(i,k,r)>eps) do

if(1-barz(i,k,r)>eps) then

is_int:=false

writeln('z fraccional, ', i, ' ', k, ' ' , r, ' barz(i,k,r)=', barz(i,k,r))

break

end-if

end-do

end-if

end-do

writeln('is_int is ... ', is_int, ' parameter XPRS_MIPINFEAS is ...', getparam("XPRS_MIPINFEAS"))

...

*****************************************************

procedure tree_cut_gen 

 setparam("XPRS_CUTSTRATEGY", 0)   ! Disable automatic cuts

 setparam("XPRS_PRESOLVE", 0)    ! Switch presolve off

 setparam("XPRS_EXTRAROWS", 5000)  ! Reserve extra rows in matrix

 feastol:= getparam("XPRS_FEASTOL") ! Get the zero tolerance

 setparam("zerotol", feastol * 10)  ! Set the comparison tolerance of Mosel

 setcallback(XPRS_CB_CM, "cb_node")

  setcallback(XPRS_CB_PREINTSOL, "cb_preintsol")

 end-procedure