result of atan is never more precise than double

3 results were exact to double the precision

20 largest ulp errors (stored in a double)
   1.02297 ulp for atan(-78661649112785.969) = -1.5707963267948837)
   1.02297 ulp for atan(-78661649112785.953) = -1.5707963267948837)
   1.02297 ulp for atan(-78661649112785.047) = -1.5707963267948837)
   1.02297 ulp for atan(-78661649112693.047) = -1.5707963267948837)
   1.02297 ulp for atan(-78661649103493.156) = -1.5707963267948837)
   1.01423 ulp for atan(855947754570165.25) = 1.5707963267948952)
   1.01423 ulp for atan(855947754570164.75) = 1.5707963267948952)
   1.01423 ulp for atan(855947754570115.88) = 1.5707963267948952)
   1.01423 ulp for atan(855947754565226.25) = 1.5707963267948952)
   0.96496 ulp for atan(-1360272459229432) = -1.5707963267948957)
   0.96496 ulp for atan(-1360272459229431.2) = -1.5707963267948957)
   0.96496 ulp for atan(-1360272459229361.2) = -1.5707963267948957)
   0.96496 ulp for atan(-1360272459222359) = -1.5707963267948957)
   0.96063 ulp for atan(-3424441040829278) = -1.5707963267948961)
   0.96063 ulp for atan(-3424441040829277.5) = -1.5707963267948961)
   0.96063 ulp for atan(-3424441040829234) = -1.5707963267948961)
   0.96063 ulp for atan(-3424441040824855.5) = -1.5707963267948961)
   0.94165 ulp for atan(-3375726820532630.5) = -1.5707963267948961)
   0.94165 ulp for atan(-3375726820532630) = -1.5707963267948961)
   0.94165 ulp for atan(-3375726820532587) = -1.5707963267948961)

<tr><td align=left><a href=atan.res>atan</a></td><td align=right>870</td><td align=right>1.02297</td><td>-78661649112785.969</td><td>-1.5707963267948837</td></tr>