use less expensive hash for proof of work

The server has to run the hash once to verify a request, so a hash that
took 4 seconds could make the server do too much work if it's being flooded
with requests.

So, made the hash much less expensive.

This required keeping track of fractional seconds. Actually, I used
Rational for them, to avoid most rounding problems. That turned out nice.

I've only tuned the proofOfWorkHashTunable on my fanless overheating
laptop so far. It seems to be fairly reasonablly tuned though.

1 files changed, 1 insertions, 1 deletions

diff --git a/Types/Cost.hs b/Types/Cost.hs
index 372c43d..4b71116 100644
--- a/Types/Cost.hs
+++ b/Types/Cost.hs
@@ -13,7 +13,7 @@ data Cost op
 	-- ^ cost in Seconds, using 1 physical CPU core
 	deriving (Show, Eq, Ord)
 
-newtype Seconds = Seconds Integer
+newtype Seconds = Seconds Rational
 	deriving (Num, Eq, Ord, Show)
 
 -- | How many CPU cores a single run of an operation can be divided amoung.