result of acosh is never more precise than double

20 largest ulp errors (stored in a double)
   1.89624 ulp for acosh(1.0078226778257107) = 0.12499999999999843)
   1.58186 ulp for acosh(1.031413099879573) = 0.24999999999999914)
   1.50904 ulp for acosh(1.1209539299999969) = 0.48701403556102812)
   1.49989 ulp for acosh(1.0075487162999484) = 0.12279444763620369)
   1.49127 ulp for acosh(1.0075487162999883) = 0.12279444763652836)
   1.33774 ulp for acosh(1.1053530086000023) = 0.45508989593356125)
   1.11356 ulp for acosh(27.308232836016476) = 3.9999999999999991)
   1.00948 ulp for acosh(27.308232836016426) = 3.9999999999999973)
   1.00761 ulp for acosh(1490.4791612521715) = 7.9999999999999947)
   1.00394 ulp for acosh(1.0078226778111077) = 0.12499999988347826)
   1.00027 ulp for acosh(27.308232836008912) = 3.999999999999722)
   1.00003 ulp for acosh(27.308232836004816) = 3.9999999999995728)
   0.99975 ulp for acosh(1490.4791612521265) = 7.9999999999999645)
   0.99966 ulp for acosh(1.0078226778256265) = 0.12499999999932696)
   0.99612 ulp for acosh(1490.4791612521635) = 7.9999999999999893)
   0.95802 ulp for acosh(1490.4791612521767) = 7.9999999999999982)
   0.91277 ulp for acosh(1.0314130998795727) = 0.24999999999999828)
   0.60042 ulp for acosh(3.1577205043999999) = 1.8169261897751663)
   0.59773 ulp for acosh(1.5430806348152439) = 1)
   0.59069 ulp for acosh(4.1142561060000933) = 2.092497640769666)

<tr><td align=left><a href=acosh.res>acosh</a></td><td align=right>1033</td><td align=right>1.89624</td><td>1.0078226778257107</td><td>0.12499999999999843</td></tr>