Improve time estimates, taking into account the number of cores.

This only affects time estimates while keysafe is generating hashes;
it does not affect cost estimates to brute-force.

1 files changed, 11 insertions, 7 deletions

diff --git a/Types/Cost.hs b/Types/Cost.hs
index 0e017bb..372c43d 100644
--- a/Types/Cost.hs
+++ b/Types/Cost.hs
@@ -9,22 +9,26 @@ module Types.Cost where
 
 -- | An estimated cost to perform an operation.
 data Cost op 
-	= CPUCost Seconds -- ^ using 1 physical CPU core
+	= CPUCost Seconds Divisibility
+	-- ^ cost in Seconds, using 1 physical CPU core
 	deriving (Show, Eq, Ord)
 
-unknownCost :: Cost op
-unknownCost = CPUCost (Seconds 0)
-
 newtype Seconds = Seconds Integer
 	deriving (Num, Eq, Ord, Show)
 
+-- | How many CPU cores a single run of an operation can be divided amoung.
+newtype Divisibility = Divisibility Integer
+	deriving (Show, Eq, Ord)
+
 data UsingHardware = UsingCPU | UsingGPU | UsingASIC
 	deriving (Show)
 
 instance Monoid (Cost t) where
-	mempty = CPUCost (Seconds 0)
-	CPUCost (Seconds a) `mappend` CPUCost (Seconds b) =
-		CPUCost (Seconds (a+b))
+	mempty = CPUCost (Seconds 0) (Divisibility 1)
+	CPUCost (Seconds a) (Divisibility x) `mappend` CPUCost (Seconds b) (Divisibility y) =
+		-- Take maximum divisibility, to avoid over-estimating
+		-- the total cost.
+		CPUCost (Seconds (a+b)) (Divisibility $ max x y)
 
 -- | Operations whose cost can be measured.
 data DecryptionOp