Elitist Jerks - View Single Post - [Mechanic Primer] - Haste

Malconstant · 04/30/08, 1:09 AM

There seems to be some confusion. It has been stated that the effect spell haste rating has on overall DPS is linear, and yet follow up responses seem to suggest a belief that there is a diminishing return in overall DPS. This is simply not the case. Even though there is a diminishing rate of decreased casting speed with spell haste rating, the increase in overall dps is constant, i.e. linear.

Consider, if the casting time of, say, a shadow bolt linearly decreased with haste rating, then a finite amount of haste rating would eventually drive the casting time down to 0 sec, which would result in dps approaching infinity. How much haste rating would result in an infinite dps? Precisely the cap, 1570. For this calculation, I am using the assumption that cast speed = 1 + (spell haste rating)/1570 , and that new casting time = (base casting time)/(cast speed). I then found the rate of decreasing casting time for spell haste rating = 0 (this is just the derivative of the new casting time as a function of spell haste rating), and followed that rate down to 0.

No one believes this model is accurate, it results in a possible infinite dps for finite haste rating, which would be an extraordinary failure on Blizzard's end. However, people do seem to believe that because the rate of casting time decrease is NOT linear, that the overall dps must ALSO be non-linear, and that is simply not the case. The impact spell haste has on dps may be calculated by:

New DPS = (Old DPS) (Old Cast Time)/(New Cast Time)

For example, consider the shadow bolt spam. Assuming one talents for the 2.5 base casting time, our (Old Cast Time) = 2.5 sec. Now suppose our lucky warlock has gathered enough spell haste rating to give a (New Cast Time) = 1.25 sec, never mind how much spell haste rating that requires (it's irrelevant for the given calculation). As you would expect, our New DPS = (Old DPS) (2.5)/(1.25) = (Old DPS) 2. So by halving our cast time, we have doubled our DPS. good. You can try out other numbers as I have if you need more convincing that this function is accurate (it is).

Therefore the effect spell haste rating has on overall DPS is to just multiply the Old DPS by (Old Cast Time)/(New Cast Time), which itself is just (Old Cast Time)/{(Old Cast Time)/[1 + (Spell Haste Rating)/1570]}. And THAT function IS linear. That is to say, the marginal effect on DPS is constant, no matter how much haste rating you have (barring the unattainable 1570 cap). Of course the OVERALL effect on DPS depends on how much haste rating you have, it is only the CHANGE in DPS that we are concerned with here.

[edited for clarity: read embarrassing errors that were quickly noted by others]

04/30/08, 1:09 AM	#132 (permalink)
Malconstant Glass Joe Malconstant Undead Warlock <Desecration> Feathermoon	The effect spell haste rating has on DPS IS linear (note: DPS does not = cast time) There seems to be some confusion. It has been stated that the effect spell haste rating has on overall DPS is linear, and yet follow up responses seem to suggest a belief that there is a diminishing return in overall DPS. This is simply not the case. Even though there is a diminishing rate of decreased casting speed with spell haste rating, the increase in overall dps is constant, i.e. linear. Consider, if the casting time of, say, a shadow bolt linearly decreased with haste rating, then a finite amount of haste rating would eventually drive the casting time down to 0 sec, which would result in dps approaching infinity. How much haste rating would result in an infinite dps? Precisely the cap, 1570. For this calculation, I am using the assumption that cast speed = 1 + (spell haste rating)/1570 , and that new casting time = (base casting time)/(cast speed). I then found the rate of decreasing casting time for spell haste rating = 0 (this is just the derivative of the new casting time as a function of spell haste rating), and followed that rate down to 0. No one believes this model is accurate, it results in a possible infinite dps for finite haste rating, which would be an extraordinary failure on Blizzard's end. However, people do seem to believe that because the rate of casting time decrease is NOT linear, that the overall dps must ALSO be non-linear, and that is simply not the case. The impact spell haste has on dps may be calculated by: New DPS = (Old DPS) (Old Cast Time)/(New Cast Time) For example, consider the shadow bolt spam. Assuming one talents for the 2.5 base casting time, our (Old Cast Time) = 2.5 sec. Now suppose our lucky warlock has gathered enough spell haste rating to give a (New Cast Time) = 1.25 sec, never mind how much spell haste rating that requires (it's irrelevant for the given calculation). As you would expect, our New DPS = (Old DPS) (2.5)/(1.25) = (Old DPS) 2. So by halving our cast time, we have doubled our DPS. good. You can try out other numbers as I have if you need more convincing that this function is accurate (it is). Therefore the effect spell haste rating has on overall DPS is to just multiply the Old DPS by (Old Cast Time)/(New Cast Time), which itself is just (Old Cast Time)/{(Old Cast Time)/[1 + (Spell Haste Rating)/1570]}. And THAT function IS linear. That is to say, the marginal effect on DPS is constant, no matter how much haste rating you have (barring the unattainable 1570 cap). Of course the OVERALL effect on DPS depends on how much haste rating you have, it is only the CHANGE in DPS that we are concerned with here. [edited for clarity: read embarrassing errors that were quickly noted by others] Last edited by Malconstant : 04/30/08 at 11:44 PM.