[Issue 255] New: Odd performance difference w/ complex doubles.

[d-bugmail at puremagic.com]

http://d.puremagic.com/issues/show_bug.cgi?id=255

           Summary: Odd performance difference w/ complex doubles.
           Product: D
           Version: 0.162
          Platform: PC
        OS/Version: All
            Status: NEW
          Severity: normal
          Priority: P2
         Component: DMD
        AssignedTo: bugzilla at digitalmars.com
        ReportedBy: godaves at yahoo.com


Version foo runs 5x slower depending on which scope the complex double
variables are declared in.

import std.stdio, std.string;
void main(char[][] args)
{
  char  bit_num = 0, byte_acc = 0;
  const int iter = 50;
  const double lim = 2.0 * 2.0;
version(foo)
{
  cdouble Z, C;
}

  int n = atoi(args[1]);

  writefln("P4\n%d %d",n,n);

  for(int y=0; y<n; y++)
    for(int x=0; x<n; x++)
    {
version(foo)
{}
else
{
       cdouble Z,C;
}
       Z = 0 + 0i;
       C = 2*cast(double)x/n - 1.5 + 2i*cast(double)y/n - 1i;

       for(int i = 0; i < iter && norm(Z) <= lim; i++)
         Z = Z*Z + C;

       byte_acc = (byte_acc << 1) | ((norm(Z) > lim) ? 0x00:0x01);

       bit_num++;
       if(bit_num == 8)
       {
           putc(byte_acc,stdout);
           bit_num = byte_acc = 0;
       }
       else if(x == n-1)
       {
           byte_acc  <<= (8-n%8);
           putc(byte_acc,stdout);
           bit_num = byte_acc = 0;
       }
    }
}

double norm(cdouble C)
{
    return C.re*C.re + C.im*C.im;
}


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