FW: [Help-glpk] bigmulin glblib05.c

[Cheng,Jen-Min]

Because MSVS 2008 would issue warning for such a conversion, the bigmul
is modified as

void bigmul(int n, int m, unsigned short x[], unsigned short y[])
{     
      int i, j;
      unsigned int t;
      union {
         unsigned int uint;
         struct { unsigned short ush1, ush2 ;} ush;
      } tuiush;

      xassert(n >= 1);
      xassert(m >= 1);
      for (j = 0; j < m; j++) x[j] = 0;
      for (i = 0; i < n; i++)
      {  if (x[i+m])
         {  t = 0;
            for (j = 0; j < m; j++)
            {  
               t += (unsigned int)x[i+m] * (unsigned int)y[j] +
                    (unsigned int)x[i+j];
               tuiush.uint = t;
               x[i+j] = (unsigned short)tuiush.ush.ush1;
//               t += (unsigned int)x[i+m] * (unsigned int)y[j] +
//                    (unsigned int)x[i+j];
//               x[i+j] = (unsigned short)t;
               t >>= 16;
            }
            x[i+m] = (unsigned short)t;
         }
      }
      return;
}

Similar modification is applied to xldiv in glplib06.c.
The modified code can converge to the solution 13.75 of vpm2.mps of
MIPLIB2003.

Andrew and Michael : Thanks your explanation.



-----Original Message-----
From: Michael Hennebry [mailto:address@hidden 
Sent: Monday, January 04, 2010 1:41 PM
To: Cheng,Jen-Min
Cc: address@hidden
Subject: Re: [Help-glpk] bigmulin glblib05.c

On Mon, 4 Jan 2010, Cheng,Jen-Min wrote:

> With MS Visual Studio 2008, unsigned int is four bytes and unsigned
> short is two bytes.  If the value of the unsigned int t is greater
than
> maximum unsigned short, how will x[i+j] = (unsigned short)t; be
> executed?  Thanks.

The manner C prescribes is x[i+j]= t mod 2**16,
assuming two bytes mans 16 bits.

-- 
Michael   address@hidden
"Pessimist: The glass is half empty.
Optimist:   The glass is half full.
Engineer:   The glass is twice as big as it needs to be."