How do Damage Reduction and multiple sources of damage from one attack interact?

[Level 1 Commoner]

How do Damage Reduction and multiple sources of damage from one attack interact?

Let's use this example.

Simon the Slasher backstabs Harry the Hamatula (DR 10/good) with his +1 Shocking Greatsword.

The rolled damage is: 25 points of weapon damage, 12 points of Sneak Attack damage and 6 points of electricity damage. But how much damage does Harry take when Damage Reduction is factored in? 33 points [(25 +12 +6) -10] points of damage or does he take 17 points of Damage [(25 -10)+ (12-10) + (6-10)]?

[Lyee]

As far as I know: Energy damage isn't reduced, but the rest is, so it would be (min(25+12-10, 0)+6) here, or 33.

[Bizbag]

It's all one attack, so it's a sum total of physical damage. Elemental damage is treated separately, but not sneak attack. Harry takes 37 points of physical damage, less 10 for DR. He also takes 6 electric damage, which he does not resist.

It's a lot like if you critically hit them - they don't get DR twice for that, either.

[Astral Wanderer]

Energy damage (acid, cold, electricity, fire or sonic) is only reduced by corresponding resistances, DR has nothing to do with it.
Sneak Attack damage, instead, is physical damage of the same type dealt by the weapon in use (bludgeoning/piercing/slashing), and is thus subject to DR.
So, Harry takes (25 normal + 12 Sneak Attack - 10 DR) + 6 electricity damage.

[Bizbag]

If it helps conceptually, DR reduces damage once per attack, regardless of the various damage dice rolled. Exceptions will be noted, like with Manyshot.

[Level 1 Commoner]

Ah ok, I never understood the difference between DR and Resistance. Now it's clear. Thanks a lot!

We're new to PF and my player are getting into the regions where both become commonplace (level 6+). Last weekend was their first fight with an Erinyes and I wanted to clarify all the questions stemming from this encounter.