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Renamed normalise to normaliseEq and stopped it being applied to inequalities (as it will fail needlessly on those!)

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This commit is contained in:
Neil Brown 2007-12-12 18:02:19 +00:00
parent 4eae0ede18
commit 4e58d48d1c
1 changed files with 12 additions and 9 deletions
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21
transformations/ArrayUsageCheck.hs
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@ -71,16 +71,19 @@ type StIneq = StateT InequalityProblem Maybe
solveConstraints :: EqualityProblem -> InequalityProblem -> Maybe InequalityProblem
solveConstraints p ineq
= normalise p >>= (\p' -> execStateT (solve p') ineq)
= normaliseEq p >>= (\p' -> execStateT (solve p') ineq)
where
normalise :: EqualityProblem -> Maybe EqualityProblem
normalise = mapM normalise' --Note the mapM; if any calls to normalise' fail, so will normalise
-- | Normalises an equation by dividing all coefficients by their greatest common divisor.
-- If the unit coefficient (a_0) doesn't divide by this GCD, Nothing will be returned
-- (the constraints do not have an integer solution)
normaliseEq :: EqualityProblem -> Maybe EqualityProblem
normaliseEq = mapM normaliseEq' --Note the mapM; if any calls to normalise' fail, so will normalise
where
normalise' :: EqualityConstraintEquation -> Maybe EqualityConstraintEquation
normalise' e | g == 0 = Just e
| ((e ! 0) `mod` g) /= 0 = Nothing
| otherwise = Just $ amap (\x -> x `div` g) e
where g = foldl1 mygcd (map abs $ tail $ elems e) -- g is the GCD of a_1 .. a_n (not a_0)
normaliseEq' :: EqualityConstraintEquation -> Maybe EqualityConstraintEquation
normaliseEq' e | g == 0 = Just e
| ((e ! 0) `mod` g) /= 0 = Nothing
| otherwise = Just $ amap (\x -> x `div` g) e
where g = foldl1 mygcd (map abs $ tail $ elems e) -- g is the GCD of a_1 .. a_n (not a_0)
mygcd :: Integer -> Integer -> Integer
mygcd 0 0 = 0
@ -116,7 +119,7 @@ solveConstraints p ineq
solveUnits p
= case findFirstUnit p of
(Nothing,p') -> return p' -- p' should equal p anyway
(Just (eq,ind),p') -> modify change >> solveUnits (change p')
(Just (eq,ind),p') -> modify change >> ((lift $ normaliseEq $ change p') >>= solveUnits)
where
change = substIn ind (arrayMapWithIndex (modifyOthersZeroSpecific ind) eq)
origVal = eq ! ind