[Help-glpk] Got a wrong order of column by lpx_get_mat_row(lp, j, ndx, val)?

[ロ コクユウ]

Dose anyone meet this problem:

 

for example  in jth row :  a*x-y+b*z=0;

 

by len=lpx_get_mat_row(lp, j, ndx, val), I found val=[-1,a,b], that mean the order of column is y,x,z.

I added two new columns to this row like:

 

ndx[len+1]=w, ndx[len+2]=v, val[len+1]=d, val[len+2]=e, len+=2

lpx_set_mat_row(lp,j,len,ndx,val)

 

then I thought the jth row should be a*x-y+b*z+d*w+e*v=0, but when I tried len=lpx_get_mat_row(lp, j, ndx, val) again,

I found it's d*w+e*v+a*x-y+b*z=0.

 

I wonder whether the order of columns in row is fixed and how the order of columns in a row is arranged there.