Justin Bailey
Massimiliano,
I had to update your code for it to compile (removed "sequence" from testpdf'. However, I don't see any significant difference in the memory profile of either testpdf or testpdf'.
Thanks Justin, indeed the two programs seems to have the same profile. I should have messed up with different versions and now I cannot reproduce the behaviour I was observing. However under Mac, Activity Monitor still gives different memory allocation to the two programs but maybe this is due to other reasons. What still I do not understand is the huge allocation of memory, but I think it is due to the way HPDF write the PDF (it has no way to understand when a page has been finished). So here's a suggestion for the library: add a pageFinalize statement which flush the page to the disk without waiting. Further addition to the same page can be either made impossible or handled by standard PDF mechanism to deal with incremental editing (see the PDF reference). Best, Massimiliano
Not sure how you are watching the memory usage, but if you didn't know the option "+RTS -sstderr" will print out useful memory statistics when you run your program. E.g.:
pdf_test.exe +RTS -sstderr
gives:
2,157,524,764 bytes allocated in the heap 246,516,688 bytes copied during GC (scavenged) 6,086,688 bytes copied during GC (not scavenged) 45,107,704 bytes maximum residency (8 sample(s)) 4086 collections in generation 0 ( 0.61s) 8 collections in generation 1 ( 0.67s) 129 Mb total memory in use INIT time 0.02s ( 0.00s elapsed) MUT time 5.83s ( 7.48s elapsed) GC time 1.28s ( 1.45s elapsed) RP time 0.00s ( 0.00s elapsed) PROF time 0.00s ( 0.00s elapsed) EXIT time 0.00s ( 0.00s elapsed) Total time 7.13s ( 8.94s elapsed) %GC time 18.0% (16.3% elapsed) Alloc rate 369,202,098 bytes per MUT second Productivity 81.8% of total user, 65.2% of total elapsed
Above you can see 45 MB was the max amount of memory ever in use - and according to the heap profiling I did it's about constant. I saw the same results when using "testpdf'".
A few tricks I've learned to reduce space usage:
* Use strict returns ( return $! ...) * foldl' over foldr unless you have to use foldr. * Profile, profile, profile - understand who is hanging on to the memory (+RTS -hc) and how it's being used (+RTS -hb). * Use +RTS -p to understand who's doing all the allocations and where your time is being spent. * Approach profiling like a science experiment - make one change, observe if anything is different, rollback and make another change - observer the change. Keep notes!
Good luck!
Justin