Torture tests: what do they mean?

[Tugdual]

(05-13-2014 10:58 PM)jebem Wrote:  This site calls my attention to how different calculators are concerning the used algorithms to get a result for a specific problem.

For example, the tan(355/226) has an ideal result of -7497258.185...
It gives me the following results (in Radian mode) for these models:

HP-Prime: -7497089.06508
HP-50G: -7497089.06508
Casio FX-991DE PLUS: -7497258.44
WP-34S: -7497258.194

Clearly the HP models algorithms deviates somehow from the expected result, contrary to what the Walter&Pauli algorithms which are giving fantastic close results.
My new acquisition, the Casio FX-991DE PLUS, is a nice surprise with a close second in this torture test, probably because it uses 15 digits internally like many others Casio calculators.

Hi Jebem,
please note that the 34s has a "double" precision mode.
I do get -7497258.185325587112905071814481370
Wolfram Alpha says that the result shall be
-7.497258185325587112905071831891248663417267943785263161571223470151837884956238​9571281869682281839570540842373435... × 10^6

So the 34s could achieve 26 digits.
Quite impressive but I will not congratulate Walter or he will think I worship him...