[Coin-discuss] Problem with MPS export / MSVC

[Jörg Herbers]

I encountered a problem when exporting an mps file via CoinMpsIO. I work on 
Microsoft Visual Studio .NET 2003 which handles printf format specification 
flags somewhat different from e.g. the gcc compiler. The problem is that 
large "infinity" upper bounds are exported as "2.147484e+00", i.e. the 
exponent is 0. CoinMpsIO::writeMps() takes the minimum over the given upper 
bound and INT_MAX (2147483647). convertDouble() converts this to a string, 
using format specification "%12.7g". The resulting string is cut after 12 
characters according to the MPS specification for the BOUNDS section. But 
while gcc converts INT_MAX into 2.147484e+09, MS VC7 (and equally MS VC6) 
converts it into 2.147484e+009, and the final "9" at position 12 will be cut 
afterwards. The Microsoft documentation says that the exponent will always 
be typeset with three digits while gcc uses two digits for exponents <100. I 
don’t know if the C++ standard defines a "correct" behaviour.

I have solved the problem in my COIN code, but I would clearly prefer a 
general solution. Several ways are viable: On the one hand, the format 
specifications could generally be changed to "%12.6g". On the other hand, 
there could be a specific solution for the Microsoft compiler, e.g. by the 
above reduction of significant digits or by a manipulation of the resulting 
string, e.g. by something like

#if defined(_MSC_VER)
    if ((outputValue[9] == '+') && (outputValue[10] == '0'))
      strcpy(&(outputValue[10]), &(outputValue[11]));
#endif

I would be very glad if you could integrate a fix into the code.

Thanks a lot,
Jörg

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