WP34S solver



#17

Hi,

I have some question about the WP34S V.3 solver:

- can I stop the solver on the real calculator if it takes too much time and how ?

- sometimes, the answer given by the solver is outside the initial domain I provided,

isn't more logic in this case that it returns a' solution not found ' message ?



Thanks.


#18

Answer to your first question: R/S will stop it at any time. EXIT will do the same. See page 81 of the manual.

Question to your second question: I don't get what you mean by 'outside the initial domain I provided'. Please specify.

Edited: 15 Mar 2012, 3:27 p.m.


#19

Quote:
Answer to your first question: R/S will stop it at any time. EXIT will do the same. See page 81 of the manual.

I admit that I haven't read carefully the manual but I remembered I've pressed EXIT and nothing is changed,

in this rarely cases calculator (v3 2641) seems frozen and I have to reset it.


Quote:
Question to your second question: I don't get what you mean by 'outside the initial domain I provided'. Please specify.


Marcus has already responded to my answer: I wrongly thought the
the solver algorithm utilized the two initial estimates as

limits for the possible solutions.


#20

A hang is always a bad thing and should never happen. If you can reproduce the case I'd be glad to analyze it.

Pauli has explained it: The two values are used as a bound if the function evaluates to opposite signs on each of the points.


#21

Hi Marcus,

unfortunately I'm not able to reproduce the solver crash but I can crash the calculator in this way:

1-reset the calculator

2-type a number

3-press very fastly ,at least twenty times ,the white down arrow key [SST]

4-without waiting repeat point 2 and 3 several times (usually 2)

at this point my calculator is frozen and I have to reset it.

Alessandro


#22

Quote:
I can crash the calculator in this way:

1-reset the calculator

2-type a number

3-press very fastly ,at least twenty times ,the white down arrow key [SST]

4-without waiting repeat point 2 and 3 several times (usually 2)

at this point my calculator is frozen and I have to reset it.


Yep, that's indeed a procedure that happens very often in every day's use! ;-)
#23

What is the current program?


#24

Hi Marcus,

my version is 2641 and there isn't a current program after I've resetted. Battery level is 2.9

I think that crash isn't caused from what keys I press but only from the speed of typing in.

I'm new to WP34 but in the first two hours I've used ,testing SLV and not making this unusual procedure,

I had to reset four times: perhaps this is only a problem of my unit.

Alessandro


#25

I can reproduce it. You are not alone :-)


#26

I must admit that I was able to reproduce the hang myself. I have no idea what goes wrong here and my hardware debugging unit is broken. I'm going to increase the probability of the fault by creating a version with a much shorter keyboard buffer. Maybe I get an idea what the cause is.


#27

The latest build contains a fix in the watch dog reset logic. In theory this should at least help to recover from any hangs. The calculator should show a "Reset" message after a few seconds.

I hope this helps.

Edit: The watch dog might well have been the culprit. It is served only when a heartbeat kicks in. With a full keyboard buffer, the heartbeats are ignored and thus it's possible that the watch dog isn't served in time. I may add another call to the watch dog reset routine if a valid keystroke is executed to avoid this.


Edited: 18 Mar 2012, 11:56 a.m.


#28

Hi Marcus,

thanks, I'll try it as soon as possible.

Alessandro

#29

"Sometimes" and "rarely" are two invincible enemies of troubleshooting. Please try to reproduce your observations under controlled conditions. We are most willing to debug, but need your support by a proper specification. Mille grazie!


#30

Quote:
"Sometimes" and "rarely" are two invincible enemies of troubleshooting. Please try to reproduce your observations under controlled conditions. We are most willing to debug, but need your support by a proper specification. Mille grazie!

I know , I'll try to reproduce the conditions that cause the crash on my calculator so you can eliminate the problem.

Thanks

Alessandro

#31

The two estimates are by no means a bound. You cannot count on the fact that the solution is between the two values in X and Y. Pauli can give you the details of the solver algorithm.


#32

The solver should stay within the two estimate if they produce function evaluations of opposite signs. Otherwise, they are just used as a guide and it is free to wander outside.

The solver uses a quadratic interpolation step but this is guarded against going to far or encountering problems with either a secant or bisection step instead.

I have code to use Ridder's method after a bisection instead of the quadratic interpolation. This is supposed to be better but I never noticed enough of an improvement to justify its inclusion and so it isn't included in the build.


- Pauli


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