Torture tests: what do they mean?

[Joe Horn]

(05-16-2014 08:52 AM)jebem Wrote:  

(05-15-2014 07:08 PM)DavidM Wrote:  Test 2:
(10^15 + 7.2 − 10^15) * 100
(...) First, make sure you're in Exact/CAS mode.

HP-Prime in CAS mode result: 400
HP-Prime Home mode: 0
Correct mathematical result: 720.
Here the WP-34S wins hands down. More digits means more probability to get a correct result. Not the other way around.

Please note that this wasn't really done in "Exact/CAS mode" as requested. The decimal point in the 7.2 forces Prime to evaluate the whole thing in approximate mode, not exact mode. If you really want to evaluate that expression in Exact/CAS mode, you must use 72/10 (or any other exact equivalent of 7.2, e.g. 7+1/5) instead of 7.2 with a decimal point in it. If you do that, you'll get the correct answer of 720 in Exact/CAS mode.