result of sqrt is never more precise than double

2 results were exact to double the precision

20 largest ulp errors (stored in a double)
   0.50000 ulp for sqrt(0.999999999999999889) = 0.999999999999999889)
   0.50000 ulp for sqrt(15.9999999999999982) = 3.99999999999999956)
   0.50000 ulp for sqrt(0.0156249999999999983) = 0.124999999999999986)
   0.50000 ulp for sqrt(0.249999999999999972) = 0.499999999999999944)
   0.50000 ulp for sqrt(63.9999999999999929) = 7.99999999999999911)
   0.50000 ulp for sqrt(0.0624999999999999931) = 0.249999999999999972)
   0.50000 ulp for sqrt(3.99999999999999956) = 1.99999999999999978)
   0.50000 ulp for sqrt(16.0000000000000036) = 4)
   0.50000 ulp for sqrt(0.0156250000000000035) = 0.125)
   0.50000 ulp for sqrt(4.00000000000000089) = 2)
   0.50000 ulp for sqrt(64.0000000000000142) = 8)
   0.50000 ulp for sqrt(1.00000000000000022) = 1)
   0.50000 ulp for sqrt(0.250000000000000056) = 0.5)
   0.50000 ulp for sqrt(0.0625000000000000139) = 0.25)
   0.50000 ulp for sqrt(2.53884156217198101e-308) = 1.59337426933284621e-154)
   0.50000 ulp for sqrt(7.05037261855188913) = 2.65525377667594897)
   0.50000 ulp for sqrt(9.53144511356327229) = 3.08730385831444742)
   0.50000 ulp for sqrt(491.057774316958671) = 22.159823427025735)
   0.50000 ulp for sqrt(0.374608653801551006) = 0.6120528194539675)
   0.50000 ulp for sqrt(3.25760941642394334e-308) = 1.80488487622450423e-154)

<tr><td align=left><a href=sqrt.res>sqrt</a></td><td align=right>1055</td><td align=right>0.50000</td><td>0.999999999999999889</td><td>0.999999999999999889</td></tr>