RE: computer-go: Sharing Go modules

["Man Lung Li" <manlungl@xxxxxxxxxxxxx>]

A one dimensional array doesn't avoid the multiply. You are doing the
multiply yourself to convert x,y to index. I think modern day optimized
compiler is more efficient than calculating the address yourself.

Man Lung Li

> -----Original Message-----
> From: David Fotland [mailto:fotland@xxxxxxxxxxxxxxxxx] 
> Sent: Wednesday, May 16, 2001 7:20 PM
> To: computer-go@xxxxxxxxxxxxxxxxx
> Subject: RE: computer-go: Sharing Go modules
> 
> 
> At 03:37 PM 5/16/2001 -0700, you wrote:
> >Could you explain why a 2D array can cause a performance problem?
> 
> 
> Take a look at the assembler output with a debugger.  To get 
> the memory address for a 2d 19x19 array, there is a multiply 
> by 19.  A one dimensional array avoids the multiply.  If the 
> computer has index addressing mode, a single instruction can 
> get the array value.
> 
> David
> 
> 
> >Thanks.
> >
> >-- Mousheng Xu
> >
> >-----Original Message-----
> >From: Anders Kierulf [mailto:anders@xxxxxxxxxxxxxxxxx]
> >Sent: Wednesday, May 16, 2001 8:33 AM
> >To: computer-go@xxxxxxxxxxxxxxxxx
> >Subject: RE: computer-go: Sharing Go modules
> >
> >
> > > The coordinate coding method that I use is X,Y converts 
> to X+Y*20. 
> > > The arrays are all 421 long where all te points at 0,Y and X,0 
> > > contain special values to make it easy to detect the edge of the 
> > > board. This is a
> >convenient
> > > coding since it's still fairly easy to see which coordinates they
> >represent
> > > (for example: 63 is 3,3 and 356 is 16,17). However I do 
> realise that 
> > > every Go programmmer has their own idea of how this 
> should be done 
> > > and that there's little chance that I can convince 
> everyone in the 
> > > world to use
> >this
> > > scheme (that would be nice though <grin>) instead of 
> using separate 
> > > X and
> >Y
> > > coordinates.
> >
> >This is a good scheme. It's the same scheme SmartGo uses, so 
> at least 
> >two Go programs have independently reached exactly the same 
> solution. 
> >Please go ahead and convince the rest of the world. :-)
> >
> >Anders Kierulf
> >www.smartgo.com
> >
> >
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> David Fotland
> 
>