there is a bug at Pain Attunement / GMP / Spell echo

Hi guys im come from taiwan server
I am building a caculator about spell damage
but when I build it , i found a weird thing about Pain Attunement + Spell echo + GMP
I use fireball to help me check the accuracy of my caculator

my fireball use
1、GMP (50% less damage)
2、Spell echo (10% less damage)
3、Pain Attunement (30% more damage)

and when I use two of them or only one to check the accuracy
it's correct , the caculation is same as game index
but when i use three of them
some weird thing happened
the effect of them become 58.005% (0.5*0.9*1.289) , not 58.5% (0.5*0.9*1.3) anymore！

my base dmg of fireball is 999 - 1498 ( with gmp and spell echo)

http://imgur.com/5ZkTnlO

you guys can see the index in the buttom

and when I ues Pain Attunement
the dmg sould be 999 * 1.3 ~ 1498 * 1.3 = 1298 ~ 1948
but it became 1287 ~ 1931 (999*1.289 ~ 1498*1.289)

http://imgur.com/DH3raMP

the base dmg is in the bottom

I dont know it is a bug or I make any mistake
dose anyone help me deal with this problem?

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i dont know the problem is about Pain Attunement or Spell echo or GMP
because as I say before, when I use two of them to check the accuracy
the index is all correct.
The problem only appears when I use all of them.

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here is my passive / gears / gems / about %increase dmg and %more or less dmg

lv19 fireball

base dmg：358 - 537

%increase dmg
1、passive：321% (fire / elemental / projectile)
2、gears：143%
3、gems：56% (Q20 fire penetration +10% , Q20 spell echo +10% , lv19 gmp +36% )

%more or less dmg
1、GMP：-50%
2、Spell echo：-10%
3、Pain Attunement：+30%

so the final base dmg should be

358 * [1 + 3.21 + 1.43 + 0.56] * 0.5 * 0.9 * 1.3 = 1298
537 * [1 + 3.21 + 1.43 + 0.56] * 0.5 * 0.9 * 1.3 = 1949

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here is all of my caculation and indexes in game

use none of them http://imgur.com/oBoqJZ7
min 358 * [1 + 3.21 + 1.43 + 0.1 (fire penatration) ] = 2055
max 537 * [1 + 3.21 + 1.43 + 0.1 (fire penatration) ] = 3082

only use GMP http://imgur.com/FOR0510

min 358 * [1+ 3.21 + 1.43 + 0.46 ] * 0.5 = 1092
max 537 * [1+ 3.21 + 1.43 + 0.46 ] * 0.5 = 1638

only use Spell echo http://imgur.com/bRoUUba

min 358 * [1 + 3.21 + 1.43 + 0.2 ] * 0.9 = 1882
max 537 * [1 + 3.21 + 1.43 + 0.2 ] * 0.9 = 2822

only use Pain Attunement http://imgur.com/rzjJ2oc

min 358 * [1 + 3.21 + 1.43 + 0.1 ] * 1.3 = 2671
max 537 * [1 + 3.21 + 1.43 + 0.1 ] * 1.3 = 4007

GMP + Spell echo http://imgur.com/RFI1DTw

min 358 * [1 + 3.21 + 1.43 + 0.56] * 0.9 * 0.5 = 999
max 537 * [1 + 3.21 + 1.43 + 0.56] * 0.9 * 0.5 = 1498

GMP + Pain Attunement http://imgur.com/sF5Wi4P

min 358 * [1 + 3.21 + 1.43 + 0.46] * 0.5 * 1.3 = 1419
max 537 * [1 + 3.21 + 1.43 + 0.46] * 0.5 * 1.3 = 2129


Spell echo + Pain Attunement http://imgur.com/80QOKjy

min 358 * [1 + 3.21 + 1.43 + 0.2] * 0.9 * 1.3 = 2446
max 537 * [1 + 3.21 + 1.43 + 0.2] * 0.9 * 1.3 = 3669

the caculations are as same as the indexes in game so far.

but when I use three of them

it sould be

358 * [1 + 3.21 + 1.43 + 0.56] * 0.5 * 0.9 * 1.3 = 1298
537 * [1 + 3.21 + 1.43 + 0.56] * 0.5 * 0.9 * 1.3 = 1949

but the index in game is like this
http://imgur.com/1Dq7Jq3

I think my caculation is right...:(

"

chriso_ov wrote:

my fireball use
1、GMP (50% less damage)
2、Spell echo (10% less damage)
3、Pain Attunement (30% more damage)


the effect of them become 58.005% (0.5*0.9*1.289) , not 58.5% (0.5*0.9*1.3) anymore！

haven't read your whole Post but aren't 'more' and/or 'less' multiplikators additive instead of multiplicative?
like multiple 'increased' and/or 'decreased' don't multiply each other but add together.

Pretty sure thats the case.

"

Vipermagi wrote:

"

Chesto wrote:

haven't read your whole Post but aren't 'more' and/or 'less' multiplikators additive instead of multiplicative?

People do use GMP + Chain. So uh. Yeah :P

Yes, but in his post he multiplies them instead of add them.
Accourding to http://pathofexile.gamepedia.com/Modifiers#Multiple_.E2.80.9CLess.E2.80.9D_and_.E2.80.9CMore.E2.80.9D_modifiers im wrong though. More is always multiplied.

most likely rounding issue related to the fact that the damage is being calculted in a slightly different way..

Vipermagi would tell you more, but I cant see the point. The divergence is less than 1%, no big deal