diff --git a/ChangeLog b/ChangeLog
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,12 @@
 ChangeLog
 
+v0.2.1.1 2014/02/05
+	(2014/02/04) PS1 - improved efficiency of square root.
+	(2014/02/04) PS1 - added profiling options.
+
+v0.2.1.0 2013/12/11
+	(2013/12/11) PS1 - added Random instance for FixedPrec.
+
 v0.2 2013/06/30
 	(2013/06/30) PS1 - fixed cabal compilation warnings.
 	(2013/05/29) PS1 - check for non-positive argument in floorlog.
diff --git a/Data/Number/FixedPrec.hs b/Data/Number/FixedPrec.hs
--- a/Data/Number/FixedPrec.hs
+++ b/Data/Number/FixedPrec.hs
@@ -57,18 +57,36 @@
 decshiftL :: Int -> Integer -> Integer
 decshiftL n x = x * 10^n
 
+-- | Return 1 + the position of the leftmost \"1\" bit of a
+-- non-negative 'Integer'. Do this in time O(/n/ log /n/), where /n/
+-- is the size of the integer (in digits).
+hibit :: Integer -> Int
+hibit 0 = 0
+hibit n = aux 1 where
+  aux k 
+    | n >= 2^k  = aux (2*k)
+    | otherwise = aux2 k (k `div` 2)    -- 2^(k/2) <= n < 2^k
+  aux2 upper lower 
+    | upper - lower < 2  = upper
+    | n >= 2^middle = aux2 upper middle
+    | otherwise = aux2 middle lower
+    where
+      middle = (upper + lower) `div` 2
+
 -- | For /n/ ≥ 0, return the floor of the square root of /n/. This is
 -- done using integer arithmetic, so there are no rounding errors.
 intsqrt :: (Integral n) => n -> n
 intsqrt n 
   | n <= 0 = 0
-  | otherwise = iterate 1 
+  | otherwise = iterate a
     where
       iterate m
         | m_sq <= n && m_sq + 2*m + 1 > n = m
         | otherwise = iterate ((m + n `div` m) `div` 2)
           where
             m_sq = m*m
+      a = 2^(b `div` 2)
+      b = hibit (fromIntegral n)
 
 -- ----------------------------------------------------------------------
 -- ** Other general-purpose functions
diff --git a/fixedprec.cabal b/fixedprec.cabal
--- a/fixedprec.cabal
+++ b/fixedprec.cabal
@@ -1,16 +1,17 @@
-Name:           fixedprec
-Version:        0.2.1.0
-License:        BSD3
+name:           fixedprec
+-- Don't forget to update the ChangeLog
+version:        0.2.1.1
+license:        BSD3
 cabal-version:  >= 1.8
-Build-type:	Simple
-License-file:   LICENSE
-Copyright:	Copyright (c) 2013 Peter Selinger
-Author:         Peter Selinger
-Maintainer:     selinger@mathstat.dal.ca
-Stability:	beta
-Category:       Data, Math
-Synopsis:       A fixed-precision real number type
-Description:
+build-type:	Simple
+license-file:   LICENSE
+copyright:	Copyright (c) 2013-2014 Peter Selinger
+author:         Peter Selinger
+maintainer:     selinger@mathstat.dal.ca
+stability:	beta
+category:       Data, Math
+synopsis:       A fixed-precision real number type
+description:
   A reasonably efficient implementation of arbitrary-but-fixed precision
   real numbers. This is inspired by, and partly based on,
   Data.Number.Fixed and Data.Number.CReal, but more efficient.
@@ -18,15 +19,18 @@
 
 extra-source-files: ChangeLog
 
-Library
-  Build-Depends:
+library
+  build-depends:
     base >= 3 && < 5, random ==1.0.*
 
-  Exposed-modules:
+  exposed-modules:
     Data.Number.FixedPrec
 
-  Ghc-Options:
+  ghc-options:
     -Wall
     -fno-warn-name-shadowing
     -fno-warn-unused-matches
     -fno-warn-type-defaults
+
+  ghc-prof-options:
+    -prof -auto-all