[Haskell-cafe] using Map rather than FiniteMap
S. Alexander Jacobson
alex at alexjacobson.com
Wed Jan 26 11:41:32 EST 2005
On Wed, 26 Jan 2005, Simon Marlow wrote:
> When using the ordinary 2-generation collector, memory in use will tend
> to be 2-3 times larger than the actual residency, because this is a
> copying collector.
Ok. Perhaps you want a different name for
this item in the reports?
>> On the other hand, I found 10mb, 5mb, and 2.5mb
>> maximum residency, but that is still ~100 bytes
>> per record.
But 100 bytes per record in a (Map Int Int) seems
awefully high. A 3 record Map would be:
(Bin 3 2 2
(Bin 1 1 1 Tip Tip)
(Bin 1 3 3 Tip Tip))
Here is how I account for memory:
size qty subtotal
Ints 4 9 36
Pointers 4 7 28
Constructors 4 7 28
Num Pairs 3
Is this accounting correct? Where do the other 70
>> Lastly, I tried "example +RTS -p -K5M -hc" and
>> then looked at the resulting graph (attachment #2)
>> and it shows a total of 1.6Mb heap allocated and
>> if that data is correct, it does correspond
>> roughly to our 20-30 bytes per record estimate.
> That profile doesn't include the stack, which sounds reasonable.
So I guess all the extra memory is actually being
allocated on the stack rather than the heap which
is a sign of a spaceleak. If I solve the
spaceleak I get the 70 bytes per item back.
> I haven't looked at your code in detail, hopefully someone else can shed
> some light on why you're building up such a large stack in the first
The code is just this 6 line program:
import qualified Map
zipped =zip [1..] [1..100000]::[(Int,Int)]
untup f (x,y) = f x y
produce = foldr (untup Map.insert) Map.empty zipped
fm = length $ Map.keys produce
main = print $ fm
Can someone tell me what I can do to make this
S. Alexander Jacobson tel:917-770-6565 http://alexjacobson.com
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