| RE: [cdt-dev] Performance problems building C++ ASTs |
Yes. Oh what joy. :)
So what should I be doing? I have tried this:
ITranslationUnit tu = ...
IIndex index = CCorePlugin.getIndexManager().getIndex(tu.getCProject());
IASTTranslationUnit ast = tu.getAST(index, ITranslationUnit.AST_SKIP_ALL_HEADERS) ;
// initially I was doing just getAST() with no args
which does indeed run much faster :) but then I can't find declarations for anything.
If I do getAST(index, 0) there is no speedup
What I'm trying to do is: walk the AST, and for each api found, determine if it's coming from a header file in a particular path.
Is there a way to only have it, say, parse the header files of the ones I'm interested in?
Then, in some other code doing some very different analysis, by a different author, we get the AST like this (I have not tested performance of this on large C++ apps because it was aimed at C-only apps anyway):
IFile file;
IASTTranslationUnit ast = CDOM.getInstance().getASTService().getTranslationUnit(file,
CDOM.getInstance().getCodeReaderFactory(CDOM.PARSE_SAVED_RESOURCES));
Pros/Cons of each way? suggestions for improving?
...Beth
Beth Tibbitts (859) 243-4981 (TL 545-4981)
High Productivity Tools / Parallel Tools http://eclipse.org/ptp
IBM T.J.Watson Research Center
Mailing Address: IBM Corp., 745 West New Circle Road, Lexington, KY 40511
"Schaefer, Doug" <Doug.Schaefer@xxxxxxxxxxxxx>
Sent by: cdt-dev-bounces@xxxxxxxxxxx 05/21/08 03:18 PM
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To be honest I don't think I ever ran the analysis on a large MPI C++ project - only on small C++ test cases, using large benchmarks projects that were C-only.
As my C++ test cases got bigger I noticed the slow down, and it *may* have been there for a long time.
Blame Greg. He found a large C++ MPI program testcase. :)
But if this helps me speed 'em all up, then that's terrific.
>apples vs. apples
The difference in time is remarkable, yes.
I don't know about #tokens but here are my rough test cases in lines of code ... tokens would be roughly proportional.
C++ loc=56 getAST() timing, three tries: 3.3,1.6,1.9 sec
C loc=80 getAST() timing, three tries: .19,.10,.03 sec
These times are just System.currentTimeMillis() before and after the getAST() call (no args. looking at using args now)
I assume the first run does some setup that the subsequent runs get to share.
I even did the C one before the C++ one once, but the times were still in the same ball park.
Repeated it a couple of times bringing up runtime workbench anew each time too - results always in the same ball park too.
This is CDT 4.0.3.200802251018
...Beth
Beth Tibbitts (859) 243-4981 (TL 545-4981)
High Productivity Tools / Parallel Tools http://eclipse.org/ptp
IBM T.J.Watson Research Center
Mailing Address: IBM Corp., 745 West New Circle Road, Lexington, KY 40511
"Schaefer, Doug" <Doug.Schaefer@xxxxxxxxxxxxx>
Sent by: cdt-dev-bounces@xxxxxxxxxxx 05/21/08 02:34 PM
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I think you can get a reference to the IIndex using CCorePlugin.getIndexManager().getIndex(tu.getCProject()).
Then call getAST() with the option ITranslationUnit.AST_SKIP_ALL_HEADERS.
This will cause the preprocessor to ignore #include directives, which is a huge performance boost. Bindings and macro calls will be resolved using the index when necessary.
I don't know if the OpenMP analysis code depends on a full parse though.
But it seems strange that parsing would be so much faster for C than C++. Are you calling the parser exactly the same way in both cases? I can see that the current code uses the CDOM.
Is CDOM something that is supposed to be deprecated eventually? Should we do it for 5.0?
Mike Kucera
Software Developer
IBM Eclipse CDT Team
mkucera@xxxxxxxxxx
Beth Tibbitts ---05/21/2008 01:14:28 PM---So how do I improve this? Can you provide some suggestions?
Sent by: cdt-dev-bounces@xxxxxxxxxxx 05/21/2008 01:13 PM
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Sent by: cdt-dev-bounces@xxxxxxxxxxx 05/21/08 01:00 PM
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I'm tracking down a performance problem (CDT 4.0.3 for now) running our PTP analysis tools on C++ code.
Getting the IASTTranslationUnit from the ITranslationUnit seems to be the culprit.
For C code,
IASTTranslationUnit atu = itranslationunit.getAST();
takes a few hundredths of a sec
For a C++ file, it takes on the order of a second and a half.
Any idea how I can speed this up? Analyzing a large C++ project is impossible at this rate.
Most of our initial analysis was on plain C code and it seems to pose no large problems.
...Beth
Beth Tibbitts (859) 243-4981 (TL 545-4981)
High Productivity Tools / Parallel Tools http://eclipse.org/ptp
IBM T.J.Watson Research Center
Mailing Address: IBM Corp., 745 West New Circle Road, Lexington, KY 40511_______________________________________________
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