Spell Fail calculation

[sanuich]

Hello

I checked the formulas that i found on wiki
http://crawl.chaosforge.org/Spell_success#Spell_skills
and i didn't get the value of spell fail that i see in game

Also i can't understand what is "You are clumsy (-2 DEX)" in my mutations list.
I don't remember where it appears. And how to remove it.

I upload my save (saves folder from game folder)

Where i missed?

[sanuich]

Here is my Exsel calculations
I got 49 if my armour Enc is 4
And 80 if 13

In game numbers are different: 30 and 99

[rockygargoyle]

The mutations screen is located on (shift) A, you can remove your mutations with a potion of cure mutations, Jiyva and Zin powers (and sometimes Xom removes mutations as well).

[neil]

Here is my Exsel calculations
I got 49 if my armour Enc is 4
And 80 if 13

In game numbers are different: 30 and 99

I can see at least a few things wrong:

• Your Armour, Earth, and Conjurations skills in the spreadsheet don't match the numbers in game (9.9, 6.8, -1 in the spreadsheet, but 8.9, 4.8, 0 in the saved game).
• Several of your formulas have a floor() that shouldn't be there. The relevant calculations use fractional skill numbers. There is some rounding depending on the formula, but AFAIK all the relevant formulas care at least down to multiples of 0.1, which is all the m screen shows anyway.
• Your formula for S_0 is spc/2 + skills/2, but that should be spc/2 + skills*2.
• The wiki's spellpower stepdown formula (that you are using in B12) isn't quite right: it doesn't account for the first step being "free" (the log formula would actually step up). The formula should only be applied if the power from step 11 is ≥ 50.
• There are two more steps after the chance you calculated in B15. First, you must apply "chance_breaks", which adjust the range (45% to -180%) to (45% to 0%) via a stepwise function. This is the step labelled "Step Down" in the wiki. This gives you "raw fail rate".
• Finally you must calculate the true fail rate from the raw fail rate ("the final step" on the wiki). The formula is in _get_true_fail_rate in the source. The wiki gives the formula for up to 33% fail, but you need two other formulas for 34-66% and 67-100%.

Edit: fixed a few things I had wrong (specifically, the spellpower stepdown as on the wiki is correct above 50).

[sanuich]

Than i missunderstood what is aptitude.
I thought that i have to add aptitude to skill.

I've red already )

[Sandman25]

http://crawl.chaosforge.org/Aptitude

[neil]

Than i missunderstood what is aptitude.
I thought that i have to add aptitude to skill.

I've red already )

Aptitude affects how much XP is required to gain a particular skill level, but doesn't change the effects of that skill level. So it takes a human (aptitude 0) twice as much XP to train Charms to level 7 as it takes a deep elf (aptitude +4), but once they're at level 7 the effects are exactly the same.