[Symphony] Suspicious Code

[Ted Ralphs]

Thanks for the report! I haven't had a chance to fix these issues yet, but
I will do so soon.

Cheers,

Ted

On Tue, Sep 16, 2014 at 7:03 AM, Konvicka Filip <Filip.Konvicka at logis.cz>
wrote:

>  Hi,
>
>
>
> While cleaning some warnings I stumbled upon several very suspicious lines
> of code in Symphony 5.5.7.
>
>
>
> Note that item 1 is a change in the headers, and unless this is fixed this
> causes warnings in programs that link libsymphony.
>
> Items 2 - 4 are possible bugs in Symphony.
>
>
>
> 1.  In OsiSolverInterface.hpp and OsiClpSolverInterface.hpp, there are
> functions defined with the default parameter values of std::string::npos.
> The type of this is size_t, but the argument for which the default is
> defined is unsigned. In 64bit builds, this leads to a truncation of the
> value.
>
>
>
>     virtual std::string getRowName(int rowIndex,
>
>                               unsigned maxLen = static_cast<unsigned>(std::string::npos))
> const;
>
>
>
> I think that it is better to use
>
>
>
>     virtual std::string getRowName(int rowIndex,
>
>                               unsigned maxLen = std::numeric_limits<
> unsigned>::max()) const;
>
>
>
> If you look at how COIN_INT_MAX is defined in CoinFinite.hpp, this is
> seems to be an acceptable COIN coding practice.  There are 5 occurrences in
> total of this (in OsiSolverInterface.hpp and OsiClpSolverInterface.hpp).
> The only use of this that I could find is OsiNames.cpp which uses this as a
> limit to std::string::substr.  Also this change should not break the ABI
> since this does not affect the symbols.
>
>
>
> 2.  In lp_heuristics.c, line 1410:
>
>
>
>        if(dive_depth > dive_depth_limit/2){
>
>           fix_incr_cnt =(int)(1.0*(frac_ip_cnt - d_fixed_cnt)/
>
>                            (dive_depth_limit > (dive_depth ?
> dive_depth_limit - dive_depth : 1)));
>
>           if(fix_incr_cnt < 1) fix_incr_cnt = 1;
>
>        }
>
>
>
> Look at the division.  The divider is a bool value! (dive_depth_limit >
> (dive_depth ? dive_depth_limit - dive_depth : 1))
>
> I think that most likely this should have been (dive_depth_limit >
> dive_depth) ? dive_depth_limit-dive_depth : 1, which by the way is
> equivalent to std::max(dive_depth_limit - dive_depth, 1).
>
>
>
>        if(dive_depth > dive_depth_limit/2){
>
>           fix_incr_cnt =(int)(1.0*(frac_ip_cnt - d_fixed_cnt)/
>
>                            ((dive_depth_limit > dive_depth) ?
> dive_depth_limit - dive_depth : 1));
>
>           if(fix_incr_cnt < 1) fix_incr_cnt = 1;
>
>        }
>
>
>
> By the way, the warning that caught the compiler's attention was -
> lp_heuristics.c(1412): warning C4804: '/' : unsafe use of type 'bool' in
> operation
>
>
>
> 3. In master_prep_base.c:504, I can also see something very suspicious:
>
>
>
>        if(P->ub < (P->mip->obj_sense == SYM_MAXIMIZE) ? -(P->mip->obj_offset)
> :
>
>            P->mip->obj_offset){
>
>
>
> This is actually evaluated as (P->ub < (P->mip->obj_sense ==
> SYM_MAXIMIZE)) ? -(P->mip->obj_offset) : P->mip->obj_offset, but obviously
> the intention was
>
>
>
>        if(P->ub < ((P->mip->obj_sense == SYM_MAXIMIZE) ? -(P->mip->obj_offset)
> :
>
>            P->mip->obj_offset)){
>
>
>
> Again the warning was master_prep_base.c(504): warning C4804: '<' : unsafe
> use of type 'bool' in operation
>
>
>
> 4. In master.c:231 and 233, there are assignments like this:
>
>
>
>    tm_par->warm_start_node_limit = (int)SYM_INFINITY;
>
>
>
> warm_start_node_limit is an int, while SYM_INFINITY is defined as 1e20
> (i.e. a double).  This does not make much sense (the conversion results in
> some strange value), so I think that it's much safer to write
>
>
>
>    tm_par->warm_start_node_limit = INT_MAX;
>
>
>
> Note that 1e20 mod (UINT_MAX+1) is the number that gets assigned, which is
> 1661992960 for 4byte ints but zero for 2byte ints.  Lucky we don't have
> small ints anymore :-)
>
>
>
> Cheers,
>
> Filip
>
>
>
> _______________________________________________
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> Symphony at list.coin-or.org
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>
>


-- 
Dr. Ted Ralphs
Associate Professor, Lehigh University
(610) 628-1280
ted 'at' lehigh 'dot' edu
coral.ie.lehigh.edu/~ted
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