result of acosh is never more precise than double

20 largest ulp errors (stored in a double)
   15308.44677 ulp for acosh(1.00000000000000022) = 2.10734242553963641e-08)
   2390.27360 ulp for acosh(1.00000000000000244) = 6.9892641303323978e-08)
   244.45396 ulp for acosh(1.0000000000000866) = 4.16166783683576424e-07)
   0.50053 ulp for acosh(1.29741217680007193) = 0.75330991099042266)
   0.50046 ulp for acosh(1.12095392999993626) = 0.487014035560908387)
   0.50042 ulp for acosh(1.36330736969994848) = 0.828515944049502018)
   0.50038 ulp for acosh(3.15772050439981955) = 1.81692618977510634)
   0.50037 ulp for acosh(1.12762596520619729) = 0.499999999999647837)
   0.50036 ulp for acosh(1.11106932700000161) = 0.46705902617123074)
   0.50035 ulp for acosh(1.43056139209698396) = 0.897535996160003569)
   0.50032 ulp for acosh(2.19500017679989057) = 1.42286181945099655)
   0.50031 ulp for acosh(1.28124451960000396) = 0.733442366478272323)
   0.50029 ulp for acosh(12.8612564290001625) = 3.24585177878055475)
   0.50027 ulp for acosh(2.52188403919999571) = 1.57630081954532475)
   0.50027 ulp for acosh(1.29204579160011224) = 0.74678447283572269)
   0.50026 ulp for acosh(1.64707883420005596) = 1.08378454134297586)
   0.50026 ulp for acosh(29.9324955006994919) = 4.0918127278999652)
   0.50025 ulp for acosh(1.20622220850001693) = 0.631664435607457664)
   0.50024 ulp for acosh(85.6832915961711876) = 5.14377096914440379)
   0.50023 ulp for acosh(1.12993122200003748) = 0.504402879147148209)

<tr><td align=left><a href=acosh.res>acosh</a></td><td align=right>1033</td><td align=right>15308.44677</td><td>1.00000000000000022</td><td>2.10734242553963641e-08</td></tr>