[LLVMdev] [GSoC] Applying for GSoC 2015
John Criswell
jtcriswel at gmail.com
Fri Mar 27 10:22:35 PDT 2015
On 3/27/15 11:55 AM, Mingxing Zhang wrote:
> Hello John,
>
> In fact I'm rushing toward a paper submission in recent days.
> Thus I'm very sorry that I do have enough time to re-write a detailed
> timeline.
I understand. I provide feedback on proposals that interest me so that
they have the greatest chance of getting accepted. That means that they
should convince not only me but other potential reviewers as well, so I
keep pushing for improvements.
It's also good exercise for writing fellowship and grant proposals.
Competing for free money is a tough business. :)
Regards,
John Criswell
> However, I've revised the "Preliminary Results" section and add some
> more information about the current prototype
> (updated both on google-melange and the url
> http://james0zan.github.io/resource/GSoC15-Proposal-BloatDetection.pdf ).
> I hope it will address your main concerns.
>
> Thank you very much!
>
>
>
> On 27 March 2015 at 03:03, John Criswell <jtcriswel at gmail.com
> <mailto:jtcriswel at gmail.com>> wrote:
>
> Dear Mingxing,
>
> Sorry for the late reply. I've been gallivanting about Europe
> giving talks and attending a conference. :)
>
> Attached is feedback on your performance diagnosis proposal. I
> think the proposal has two flaws which, if possible, you should
> rectify before the deadline tomorrow:
>
> 1) It is not clear what the current prototype can do and how well
> it works. Is it implemented only in PIN, or also in LLVM? If in
> LLVM, how far along is that prototype, and how well does it
> perform? What is missing from it that you want to implement for GSoC?
>
> 2) Your reasoning for why dynamic slicing is going to work is
> flawed. You assume that Giri is slow because it instruments a lot
> of instructions. That is incorrect. Giri is slow because it
> generates so much data during program execution that this data
> cannot be kept in memory and must therefore be flushed to
> persistent storage (which was magnetic disk at the time we wrote
> it). If instrumentation just needs to update data structures, you
> get 2x-4x slowdown and life is slow but livable. If you're
> streaming tons of data to disk about every load, store, and
> branch, that's another thing entirely.
>
> I realize that the time to the deadline is short, but if possible,
> please improve your proposal before the deadline. Despite the
> above issues, I find your proposal interesting and would like to
> see it have the best chance possible of being accepted for GSoC.
>
> Regards,
>
> John Criswell
>
>
>
> On 3/16/15 11:55 AM, Mingxing Zhang wrote:
>> Thank you very much for all your advices!
>> I'll revise the proposal according to them.
>>
>> To George,
>>
>> As mentioned in the former emails of this thread, I intend to
>> prepare two proposals for the AA project listed in the idea list
>> and the bloat detection project proposed by myself respectively
>> and at most one of them will be accepted by GSoC.
>> Personally, I do prefer the second project since I'm more
>> familiar with that field and the technique (static
>> instrumentation) it uses.
>>
>> According to the timeline of GSoC
>> <https://www.google-melange.com/gsoc/document/show/gsoc_program/google/gsoc2015/help_page>,
>> the accepted proposals will only be announced at 27 April. Is it
>> too late since I do not know which project will be selected or
>> even none of them will be accepted until then?
>> Otherwise, will the mentors know the decision earlier (e.g., at
>> 15 April after the slot is allocated to organizations)?
>>
>>
>> To John,
>>
>> The proposal for bloat detection is also available now at
>> http://james0zan.github.io/resource/GSoC15-Proposal-BloatDetection.pdf
>> (not completely finished yet).
>> Some preliminary evaluation results on overhead and detecting
>> ability based on a simple prototype are given.
>> (Actually I came up with this idea during my visitation in
>> Columbia U and the prototype is also implemented at those days,
>> but the project is paused until recent days due to my internship
>> in Google and some other works.)
>>
>> P.S. The tex template is downloaded at
>> http://www.latextemplates.com/template/large-colored-title-article.
>>
>> Once again, thank you for your time!
>>
>>
>> On 16 March 2015 at 02:58, George Burgess IV
>> <george.burgess.iv at gmail.com
>> <mailto:george.burgess.iv at gmail.com>> wrote:
>>
>> CFLAA already has some basic interprocedural analysis built
>> in (see: tryInterproceduralAnalysis; it basically boils down
>> to CFLAA grabbing the StratifiedSets for each function call
>> and unifying sets based off of that instead of unifying
>> everything ever). The only real changes I had in mind for it
>> were:
>>
>> - Adding context sensitivity (which kind of requires adding
>> context sensitivity to CFLAA first)
>> - Making it less terrible for {mutually,indirectly,}
>> recursive functions (While we're building the sets for some
>> function A(), the sets for A() aren't accessible, so any call
>> to A() from a function called by A() looks opaque).
>>
>> If you want to take a stab at making IPA better/adding
>> context sensitivity, you're more than welcome to do so. I'm
>> happy to work on other things in the meantime :)
>>
>> George
>>
>> On Sun, Mar 15, 2015 at 8:50 AM, Mingxing Zhang
>> <james0zan at gmail.com <mailto:james0zan at gmail.com>> wrote:
>>
>> Hello Daniel,
>>
>> Thank you for your comments and sorry for my mistakes,
>> I'll revise them.
>> And I'll for sure read the paper you mentioned and survey
>> the recent researches before deciding the implementation
>> technique.
>>
>> To George:
>> May I know the exact plan of your attempt for making
>> cfl-aa interprocedural?
>> I do think that this is the most valuable part of my
>> proposal, but that makes no sense to do it twice.
>>
>> Maybe I can work on the porting of the flow-sensitive
>> method proposed by Prof. Ben Hardekopf at CGO11
>> <http://www.cs.ucsb.edu/%7Ebenh/research/papers/hardekopf11flow.pdf>.
>> It is declared in his homepage that the published source
>> code "is written for a pre-release version of LLVM 2.5
>> and does not work in current versions of LLVM"
>>
>> Thanks!
>>
>>
>>
>> On 15 March 2015 at 08:31, Daniel Berlin
>> <dberlin at dberlin.org <mailto:dberlin at dberlin.org>> wrote:
>>
>> A few notes:
>> 1. "But these standard LLVM AA passes either take a
>> large amount of time (Anderson Analysis at cubic time
>> and large memory requirements)"
>>
>> Neither of these is correct. Andersen's is not cubic
>> in practice, or large memory in practice, when
>> implemented properly. GCC uses it by default as the
>> points-to implementation, and it's never even close
>> to the top of the profile.
>>
>> It takes about 1 second to do a million lines of code.
>> And one can do better (gcc's impl is no longer state
>> of the art).
>>
>> 2. The approach to field sensitivity you mention is
>> not going to work very well, given how much casting
>> occurs (everything is casted). I would suggest using
>> the approach in http://dl.acm.org/citation.cfm?id=996835
>>
>> 3. George, cc'd, is planning on implementing both
>> context sensitive and context-insensitive
>> interprocedural analysis in cfl-aa the next month or
>> two.
>>
>> 4. Using a BDD cloning approach for CFL-AA doesn't
>> make much sense, the whole point of CFL is not having
>> to generate explicit points-to sets if you don't want
>> to. Plus, followup papers and researchers have
>> *never* been able to reproduce the scalability of
>> Whaley's work.
>>
>> Not to mention it's done on Java. Java is a language
>> where doing things like field-sensitivity always
>> increase precision, which is not true for C.
>>
>> If you really want to attempt this, I would suggest
>> using one of the demand driven context-sensitive
>> approaches that will be easy to fit in CFL.
>>
>> On Sat, Mar 14, 2015 at 5:57 AM Mingxing Zhang
>> <james0zan at gmail.com <mailto:james0zan at gmail.com>> wrote:
>>
>> Hello John,
>>
>> I've finished the first version of my proposal on
>> enhancing alias analysis.
>> The proposal can be downloaded at
>> http://james0zan.github.io/resource/GSoC15-Proposal-AA.pdf.
>> I hope I've successfully justified the necessity
>> and benefits of this project.
>> If possible, please find some time to review it
>> and give me some more feedbacks.
>>
>> Thank you very much!
>>
>> P.S. I'm working on the other proposal, a couple
>> of days is needed.
>>
>>
>>
>> On 8 March 2015 at 21:42, Mingxing Zhang
>> <james0zan at gmail.com
>> <mailto:james0zan at gmail.com>> wrote:
>>
>> Got it.
>> I'll try to find the applications for
>> field-sensitivity (and interprocedural, etc)
>> AA analysis.
>> And I'll do some preliminary evaluation on
>> the tracing/slicing part for the bloat detection.
>>
>> Thanks!
>>
>> On 8 March 2015 at 21:34, John Criswell
>> <jtcriswel at gmail.com
>> <mailto:jtcriswel at gmail.com>> wrote:
>>
>> On 3/8/15 8:56 AM, Mingxing Zhang wrote:
>>> Hello John,
>>>
>>> According to the FAQ, I can submit two
>>> proposals although at most one of them
>>> can be accepted.
>>> Thus I will prepare a proposal for each
>>> of the two projects.
>>
>> Correct. Only one proposal will be accepted.
>>
>>
>>> And, after reading the code of cfl-aa
>>> and several related papers, I've listed
>>> four milestones for the AA project:
>>>
>>> 1) In order to use the fast algorithm
>>> described in PLDI'13 [1], cfl-aa makes a
>>> simplification on the CFL defined in
>>> POPL'08 [2], which will lead to a
>>> reduction on precision (I've confirmed
>>> this observation with the author).
>>> Thus a quantitative measurement on how
>>> much is the reduction is needed.
>>>
>>> 2) In cfl-aa, different fields of a same
>>> struct and the whole array are
>>> represented by a single node.
>>> This is the reason of the problem 2, 4
>>> listed in http://llvm.org/OpenProjects.html.
>>> We should split these large nodes.
>>
>> I think the real question is whether the
>> loss of precision matters, and if so, to
>> which uses of alias analysis. SAFECode,
>> for example, wants field information to
>> determine type safety (so that it can
>> optimize away type-safe loads and
>> stores), so field sensitivity matters.
>> Perhaps field sensitivity doesn't matter
>> for other applications (e.g.,
>> optimization). There's no point in
>> improving precision if it doesn't help
>> the analyses that people care about most.
>>
>> As part of your project, I think you
>> should state the uses of alias
>> analysis/points-to analysis that you're
>> aiming to improve and understand whether
>> your proposed improvements will help that
>> use. I would also recommend picking a
>> use that matters to a significant portion
>> of the LLVM community.
>>
>>>
>>> 3) Handling special global variables,
>>> such as errno.
>>>
>>> 4) It seems that the current version of
>>> cfl-aa is an intraprocedural analysis.
>>> If the time is enough, I think we may
>>> extend it to an interprocedural analysis.
>>> The algorithm described in [3] can be
>>> applied to scaling it.
>>>
>>> As for the bloat-detection project, the
>>> final result should be a tool that is
>>> verified by known bugs and a set of
>>> newly detected bugs.
>>
>> For the bloat detection tool, I would
>> like to be convinced that dynamic tracing
>> will be, or can be, sufficiently
>> efficient to be practical. I hate to ask,
>> but I think you need to run an experiment
>> with Giri to show that dynamic slicing is
>> going to be practical for the executions
>> that you expect to analyze. Either that,
>> or you need to explain how you can use
>> something more efficient than dynamic
>> slicing (note that dynamic slicing and
>> dynamic tracing are not the same, so be
>> sure you're correctly stating which one
>> you need).
>>
>>>
>>> Do you have any suggestions on these
>>> objectives?
>>
>> In your proposal, be sure to include a
>> set of milestones and how long you think
>> you will need to achieve those
>> milestones. I may have said that before,
>> but it's worth repeating.
>>
>> Regards,
>>
>> John Criswell
>>
>>
>>>
>>> Thanks!
>>>
>>>
>>> [1] Fast Algorithms for
>>> Dyck-CFL-Reachability with Applications
>>> to Alias Analysis. PLDI'13
>>> [2] Demand-Driven Alias Analysis for C.
>>> POPL'08
>>> [3] Demand-Driven Context-Sensitive
>>> Alias Analysis for Java. ISSTA'11
>>>
>>>
>>> On 5 March 2015 at 09:58, Mingxing Zhang
>>> <james0zan at gmail.com
>>> <mailto:james0zan at gmail.com>> wrote:
>>>
>>> Wow, that is cool!
>>> I'll check about it.
>>>
>>> Thank you!
>>>
>>> On 4 March 2015 at 21:57, John
>>> Criswell <jtcriswel at gmail.com
>>> <mailto:jtcriswel at gmail.com>> wrote:
>>>
>>> On 3/4/15 2:18 AM, Mingxing
>>> Zhang wrote:
>>>> Hello John,
>>>>
>>>> Thank you for your advices and
>>>> congratulations~
>>>>
>>>> I'll read the code of cfl-aa
>>>> and Giri first and make the
>>>> decision of which project to
>>>> pursue.
>>>> The choice will be reported to
>>>> this thread once I made the
>>>> determination (hopefully within
>>>> this week).
>>>
>>> You should check for yourself,
>>> but I don't think anything
>>> prevents you from submitting two
>>> proposals. If you have time to
>>> write two strong proposals, I
>>> see no problem with that.
>>>
>>> Just make sure that any proposal
>>> you write is strong: it provides
>>> a concrete explanation of what
>>> you want to do, some
>>> justification for why it would
>>> benefit the community (short or
>>> long term), and why you're the
>>> person qualified to do it.
>>> Proposals should also include a
>>> set of milestones and expected
>>> dates for completing those
>>> milestones.
>>>
>>> Regards,
>>>
>>> John Criswell
>>>
>>>
>>>>
>>>> Thanks!
>>>>
>>>>
>>>> On 3 March 2015 at 23:12, John
>>>> Criswell <jtcriswel at gmail.com
>>>> <mailto:jtcriswel at gmail.com>>
>>>> wrote:
>>>>
>>>> Dear Mingxing,
>>>>
>>>> I think both projects are
>>>> interesting and useful.
>>>>
>>>> Points-to analysis is
>>>> something that is needed by
>>>> research users of LLVM, but
>>>> to the best of my
>>>> knowledge, no solid
>>>> implementation currently
>>>> exists (although the cfl-aa
>>>> work being done at Google
>>>> may provide us with
>>>> something; you should check
>>>> into it before writing a
>>>> proposal). My interest is
>>>> in a points-to analysis
>>>> that is robust and is
>>>> useful to both research and
>>>> industry users of LLVM. A
>>>> points-to analysis proposal
>>>> must indicate how it will
>>>> help both of these subsets
>>>> of the LLVM community, and
>>>> it must argue why current
>>>> efforts do not meet the
>>>> requirements of both
>>>> subsets of the community.
>>>>
>>>> The runtime bloat tool also
>>>> looks interesting, and your
>>>> approach (at least to me)
>>>> is interesting. One
>>>> question in my mind,
>>>> though, is whether dynamic
>>>> slicing is going to work
>>>> well. Swarup Sahoo and I
>>>> built a dynamic slicer for
>>>> LLVM named Giri, and we
>>>> found the tracing required
>>>> for dynamic slicing to be
>>>> slow. For our purposes,
>>>> the overhead was okay as we
>>>> only needed to record
>>>> execution until a crash
>>>> (which happened quickly).
>>>> In your bloat tool, the
>>>> program will probably run
>>>> for awhile, creating a long
>>>> trace record. You should
>>>> take a look at the Giri
>>>> code, use it to trace some
>>>> programs, and see if the
>>>> overheads are going to be
>>>> tolerable. If they are
>>>> not, then your first task
>>>> would be to optimize Giri
>>>> for your bloat tool.
>>>>
>>>> You should also be more
>>>> specific about which LLVM
>>>> instructions will be
>>>> traced. For example, I
>>>> wouldn't record the outputs
>>>> of every LLVM instruction;
>>>> I might only record the
>>>> outputs of loads and stores
>>>> or the end of a def-use chain.
>>>>
>>>> I'd be interested in
>>>> mentoring either project.
>>>>
>>>> BTW, it looks like your FSE
>>>> paper won an award. Congrats.
>>>>
>>>> Regards,
>>>>
>>>> John Criswell
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>>
>>>> On 3/3/15 2:30 AM, Mingxing
>>>> Zhang wrote:
>>>>> Hi all,
>>>>>
>>>>> As a Ph.D. student majored
>>>>> in Software Reliability, I
>>>>> have used LLVM in many of
>>>>> my projects, such as the
>>>>> Anticipating Invariant
>>>>> (http://james0zan.github.io/AI.html)
>>>>> and some other undergoing
>>>>> ones.
>>>>> Thus, it would be a great
>>>>> pleasure for me if I could
>>>>> take this opportunity to
>>>>> contribute to this awesome
>>>>> project.
>>>>>
>>>>> After reading the idea
>>>>> list
>>>>> (http://llvm.org/OpenProjects.html),
>>>>> I was most interested in
>>>>> the idea of improving the
>>>>> "Pointer and Alias
>>>>> Analysis" passes.
>>>>> Could you please give me
>>>>> some more tips or advices
>>>>> on how to get started on
>>>>> working on the application?
>>>>>
>>>>> Simultaneously, I also
>>>>> have another idea about
>>>>> using LLVM to detect
>>>>> runtime bloat, just like
>>>>> the ThreadSanitizer tool
>>>>> for data races.
>>>>> If there is anyone here
>>>>> who would like to mentor
>>>>> this project, could you
>>>>> please find some time to
>>>>> review the more detailed
>>>>> proposal on gist
>>>>> <https://gist.github.com/james0zan/d03737c60b10d0d11d34>
>>>>> and give me some feedbacks?
>>>>>
>>>>> P.S.
>>>>> I do prefer the bloat
>>>>> detection tool, but I'm
>>>>> not sure about whether it
>>>>> is suitable for GSoC.
>>>>> Thus I will apply for
>>>>> the Alias Analysis one if
>>>>> it is not suitable.
>>>>>
>>>>> Thanks!
>>>>>
>>>>> --
>>>>> Mingxing Zhang
>>>>>
>>>>> Tel.: +86-10-62797143
>>>>> <tel:%2B86-10-62797143>
>>>>> Web:
>>>>> http://james0zan.github.io/
>>>>> Addr: Room 3-122, FIT
>>>>> Building, Tsinghua
>>>>> University, Beijing
>>>>> 100084, China
>>>>>
>>>>>
>>>>> _______________________________________________
>>>>> LLVM Developers mailing list
>>>>> LLVMdev at cs.uiuc.edu <mailto:LLVMdev at cs.uiuc.edu> http://llvm.cs.uiuc.edu
>>>>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>>> /
>>>>
>>>> --
>>>> John Criswell
>>>> Assistant Professor
>>>> Department of Computer Science, University of Rochester
>>>> http://www.cs.rochester.edu/u/criswell
>>>>
>>>>
>>>>
>>>>
>>>> --
>>>> Mingxing Zhang
>>>>
>>>> Tel.: +86-10-62797143
>>>> <tel:%2B86-10-62797143>
>>>> Web: http://james0zan.github.io/
>>>> Addr: Room 3-122, FIT Building,
>>>> Tsinghua University, Beijing
>>>> 100084, China
>>>
>>>
>>> --
>>> John Criswell
>>> Assistant Professor
>>> Department of Computer Science, University of Rochester
>>> http://www.cs.rochester.edu/u/criswell
>>>
>>>
>>>
>>>
>>> --
>>> Mingxing Zhang
>>>
>>> Tel.: +86-10-62797143
>>> <tel:%2B86-10-62797143>
>>> Web: http://james0zan.github.io/
>>> Addr: Room 3-122, FIT Building,
>>> Tsinghua University, Beijing 100084,
>>> China
>>>
>>>
>>>
>>>
>>> --
>>> Mingxing Zhang
>>>
>>> Tel.: +86-10-62797143
>>> <tel:%2B86-10-62797143>
>>> Web: http://james0zan.github.io/
>>> Addr: Room 3-122, FIT Building, Tsinghua
>>> University, Beijing 100084, China
>>
>>
>> --
>> John Criswell
>> Assistant Professor
>> Department of Computer Science, University of Rochester
>> http://www.cs.rochester.edu/u/criswell
>>
>>
>>
>>
>> --
>> Mingxing Zhang
>>
>> Tel.: +86-10-62797143 <tel:%2B86-10-62797143>
>> Web: http://james0zan.github.io/
>> Addr: Room 3-122, FIT Building, Tsinghua
>> University, Beijing 100084, China
>>
>>
>>
>>
>> --
>> Mingxing Zhang
>>
>> Tel.: +86-10-62797143 <tel:%2B86-10-62797143>
>> Web: http://james0zan.github.io/
>> Addr: Room 3-122, FIT Building, Tsinghua
>> University, Beijing 100084, China
>> _______________________________________________
>> LLVM Developers mailing list
>> LLVMdev at cs.uiuc.edu <mailto:LLVMdev at cs.uiuc.edu>
>> http://llvm.cs.uiuc.edu
>> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>>
>>
>>
>>
>> --
>> Mingxing Zhang
>>
>> Tel.: +86-10-62797143 <tel:%2B86-10-62797143>
>> Web: http://james0zan.github.io/
>> Addr: Room 3-122, FIT Building, Tsinghua University,
>> Beijing 100084, China
>>
>>
>>
>>
>>
>> --
>> Mingxing Zhang
>>
>> Tel.: +86-10-62797143 <tel:%2B86-10-62797143>
>> Web: http://james0zan.github.io/
>> Addr: Room 3-122, FIT Building, Tsinghua University, Beijing
>> 100084, China
>
>
> --
> John Criswell
> Assistant Professor
> Department of Computer Science, University of Rochester
> http://www.cs.rochester.edu/u/criswell
>
>
>
>
> --
> Mingxing Zhang
>
> Tel.: +86-10-62797143
> Web: http://james0zan.github.io/
> Addr: Room 3-122, FIT Building, Tsinghua University, Beijing 100084, China
--
John Criswell
Assistant Professor
Department of Computer Science, University of Rochester
http://www.cs.rochester.edu/u/criswell
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