[Haskell-cafe] using Map rather than FiniteMap

S. Alexander Jacobson alex at alexjacobson.com
Wed Jan 26 09:28:58 EST 2005

Ah, ok.  So I ran the code with 100000 items, 
50000 items, and 25000 items and got total memory 
in use of 28Mb, 15Mb, and 8Mb respectively.  That 
comes to 260-280 bytes per record which is still 
an order of magnitude higher than the 20-30 bytes 
per record we would expect.

On the other hand, I found 10mb, 5mb, and 2.5mb 
maximum residency, but that is still ~100 bytes 
per record.

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.

Regarding stack, I tried "example +RTS -p -K5M -xt 
-hc" and then ran hp2ps and looked at the 
resulting graph (attachment #1) SYSTEM appears to 
use 4mb of stack at the very beginning (presumably 
to create "zipped"), but I don't know why it 
would.  Then this stack is consumed by the rest of 
the program.

Can you provide some guidance on interpreting this 


S. Alexander Jacobson tel:917-770-6565 http://alexjacobson.com

On Wed, 26 Jan 2005, Simon Marlow wrote:

> On 25 January 2005 23:27, S. Alexander Jacobson wrote:
>> Oops.  It pays to check your checking code before
>> making posts like this.
>> After actually running the correct test, I am
>> still getting semi-ridiculous space behavior
>> (6k/pair)!
>>     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
>> Has this profile:
>>  	   example +RTS -p -K5M -RTS
>>  	total time  =        5.10 secs   (255 ticks @ 20 ms)
>>  	total alloc = 612,534,236 bytes  (excludes profiling overheads)
>>     	COST CENTRE                    MODULE               %time %alloc
>>  	balance                        Map                   71.8   72.8
>>  	insert                         Map                   12.2   10.8
>>  	size                           Map                    9.0    9.7
>>  	bin                            Map                    2.4    2.2
>>  	rotateR                        Map                    1.6    0.3
>>  	zipped                         Main                   0.8    1.9
>> Notice the 612Mb for storing a mapping from Int
>> to Int!!
> Notice that's 612Mb *allocation* to create the finite map and
> deconstruct it into a list.  Not 612Mb of live heap to store the finite
> map.  If you make sure everything is evaluated, and examine the heap
> profile I'm sure you'll find that the finite map is taking a reasonable
> amount of space (perhaps 20-30 bytes per node for storing integers, I
> guess).
> To get a rough idea of the total live heap without profiling, you can
> run the program with +RTS -sstderr and look at the memory "in use"
> figure.
> Cheers,
> 	Simon
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