Re: [Gcl-devel] hash redux

[Jared C. Davis]

Hi,

For this benchmark you may want to compare GCL against any other Lisp
besides CCL, because we use a different hashing scheme in CCL than in
other Lisps.

Cheers,
Jared

On Tue, Nov 12, 2013 at 8:04 AM, Matt Kaufmann <address@hidden> wrote:
> Hi, Camm --
>
> Here's a comparable CCL time:
>
> ; 37.65 seconds realtime, 36.99 seconds runtime
> ; (3,473,050,544 bytes allocated).
>
> Although that's about half the time it takes GCL, I think that may be
> quite outstanding for GCL, given that CCL is optimized specifically
> for the "(h)" part of ACL2(h).
>
> -- Matt
>    From: Camm Maguire <address@hidden>
>    Cc: "Jared C. Davis" <address@hidden>, address@hidden
>    Date: Tue, 12 Nov 2013 08:04:10 -0500
>
>    Greetings!  Before we look further, let me run this in gdb.  I have
>    encountered situations in which the gprof profilier fails to detect the
>    end of certain (optimized, inlined) functions and misreports the
>    statistics.  More later when I get this done.
>
>    Matt, I was trying the same in ccl just to see where we stand, and could
>    not load the portcullis.  Do you happen to have a comparable ccl time
>    for this handy?
>
>    Take care,
>
>    Matt Kaufmann <address@hidden> writes:
>
>    > Hi, Jared and Camm --
>    >
>    > I ran the experiment you suggested, Jared (thanks for the suggestion).
>    > In books/centaur/gl/:
>    >
>    > (ubt! 1)
>    > (include-book "portcullis")
>    > (rebuild "solutions.lisp" t)
>    > (u)
>    > (time$ (def-gl-thm 1f
>    >   :hyp (and (unsigned-byte-p 3000 x)
>    >             (unsigned-byte-p 3000 y))
>    >   :concl (equal (+ x y) (+ y x))
>    >   :g-bindings (gl::auto-bindings (:mix (:nat x 3000)
>    >                                        (:nat y 3000)))))
>    >
>    > That took 78 seconds (a very nice improvement!).  Then:
>    >
>    > ACL2 !>:q
>    >
>    > Exiting the ACL2 read-eval-print loop.  To re-enter, execute (LP).
>    > ACL2>(hons-summary)
>    >
>    > Normed Objects Summary
>    >
>    >  - NIL-HT:                     4 count,           5,000 size ( 0.08% 
> full)
>    >  - CDR-HT:             9,071,974 count,      12,974,622 size (69.92% 
> full)
>    >  - CDR-HT-EQL:                 0 count,           1,000 size ( 0.00% 
> full)
>    >  - STR-HT:                     1 count,           1,000 size ( 0.10% 
> full)
>    >  - PERSIST-HT:                 0 count,             100 size ( 0.00% 
> full)
>    >  - FAL-HT:                     0 count,           1,000 size ( 0.00% 
> full)
>    >
>    > NIL
>    >
>    > ACL2>(hl-hspace-str-ht *default-hs*)
>    >
>    > #<hash-table 0000000004e06af0>
>    >
>    > ACL2>
>    >
>    > (I did some searching and did find another 'equal hash table besides
>    > that str-ht, namely; *hcomp-book-ht*, but it's quite small and not
>    > relevant here.)
>    >
>    > So I'm again stumped, since the cdr-ht is, I think, an 'eq hash
>    > table.
>    >
>    > Camm, is there a way to identify the callers that are setting a hash
>    > table with test 'equal?  The profile you sent seems to be at the level
>    > of C, so I don't know what to trace.
>    >
>    > -- Matt
>    >    From: "Jared C. Davis" <address@hidden>
>    >    Date: Mon, 11 Nov 2013 16:18:24 -0600
>    >    Cc: Camm Maguire <address@hidden>,
>    >       "address@hidden" <address@hidden>
>    >
>    >    Hi,
>    >
>    >    I believe Matt is correct that the only use of EQUAL hash tables in
>    >    the (h) part of ACL2(h) is for string hashing.  In fact, for the most
>    >    part, in a single-threaded context, I think there should typically be
>    >    just a single string hash table.
>    >
>    >    At the relevant part of your benchmark, you might run (hons-summary)
>    >    to see the size and count of this table, in case that's helpful.  Or
>    >    if you want to get your hands on the hash table to really take a deep
>    >    look at it, you can try, e.g.,:
>    >
>    >    ACL2 !>(hons "foo" "bar")
>    >    ("foo" . "bar")
>    >    ACL2 !>:q
>    >    :q
>    >
>    >    Exiting the ACL2 read-eval-print loop.  To re-enter, execute (LP).
>    >    ? (hl-hspace-str-ht *default-hs*)
>    >    #<HASH-TABLE :TEST EQUAL size 2/1000 #x30200EA5441D>
>    >
>    >    Cheers,
>    >    Jared
>    >
>    >    On Mon, Nov 11, 2013 at 3:21 PM, Matt Kaufmann <address@hidden> wrote:
>    >    > Hi, Camm --
>    >    >
>    >    > That's interesting, but I'm confused, and I'm definitely not an 
> expert
>    >    > on hash tables.  I looked at the files that implement the "(h)" part
>    >    > of ACL2(h), which is almost certainly what is involving hash tables,
>    >    > and it looks to me like maybe the only 'equal hash tables are for
>    >    > strings.
>    >    >
>    >    > I'm forwarding this to Jared, since he is the most recent author of
>    >    > that code (plus, you mention him as helping with potentially related
>    >    > reader issues), in case he has time to shed light on this.
>    >    >
>    >    > -- Matt
>    >    >    From: Camm Maguire <address@hidden>
>    >    >    Date: Mon, 11 Nov 2013 12:49:41 -0500
>    >    >
>    >    >    Greetings!
>    >    >
>    >    >    Just a followup -- the remaining time appears to be in sethash 
> for an
>    >    >    'equal hash-table:
>    >    >
>    >    >    
> =============================================================================
>    >    >    index % time    self  children    called     name
>    >    >                                 103979625             sethash [1]
>    >    >    [1]     84.2    2.11   49.03       0+103979625 sethash [1]
>    >    >                   22.58    6.16 167566772/167566772     
> fShash_equal [2]
>    >    >                    0.00   20.28  119656/131885      alloc_relblock 
> [6]
>    >    >                    0.01    0.00  119656/205048      alloc_object 
> [47]
>    >    >                                 103979625             sethash [1]
>    >    >    -----------------------------------------------
>    >    >                   22.58    6.16 167566772/167566772     sethash [1]
>    >    >    [2]     47.3   22.58    6.16 167566772         fShash_equal [2]
>    >    >                    5.25    0.00 363849475/363849475     hash_eql 
> [12]
>    >    >                    0.91    0.00 1174935219/1174940911     eql1 [18]
>    >    >                    0.00    0.00      12/2577623     Fand <cycle 2> 
> [151]
>    >    >    -----------------------------------------------
>    >    >                    0.29    5.78       3/14          make_cons [9]
>    >    >                    1.06   21.19      11/14          alloc_relblock 
> [6]
>    >    >    [3]     46.6    1.35   26.97      14         GBC [3]
>    >    >                   26.93    0.00 25304834/25331171     
> sgc_mark_object1 <cycle 1> [5]
>    >    >    
> =============================================================================
>    >    >
>    >    >    This is somewhat remarkable, as the 'eql gethash calls which 
> greatly
>    >    >    dominate in number are no longer on the radar.  Presumably the 
> algorithm
>    >    >    makes some complex cons, (definitely not your grandmother's '(1 
> 2 3)
>    >    >    list), uses an 'equal hashtable to make it equal-unique, and 
> then uses
>    >    >    that as a key in an 'eql hashtable for the real heavy work.
>    >    >
>    >    >    This just reminded me of the work we did earlier regarding the 
> loading
>    >    >    of complex conses in compiled files, which overloaded the #= 
> reader
>    >    >    until we memoized the routine calculating the hash-equal index.  
> This is
>    >    >    barely necessary to the gcl compiler -- the point is to catch 
> errors
>    >    >    where the constant list to be compiled in changes during 
> compilation.
>    >    >    And as I indicated earlier, we flush the memoizing hash tables 
> on each
>    >    >    compile-file.  This, together with the implementation of the 
> 'hybrid' #=
>    >    >    algorithm suggested by Jared, made the loading of these conses 
> very
>    >    >    fast.
>    >    >
>    >    >    My question is if we've learned anything which might make the 
> above
>    >    >    results yet faster.  By default, the hash-equal index descends 
> no more
>    >    >    than three levels, car and cdr, into a cons to xor up the index. 
>  It
>    >    >    does not attempt to descend the entire structure memoizing as 
> one goes
>    >    >    like the compiler version.  There the depth limit is much 
> greater (1000)
>    >    >    due to its purpose and the absence of any table.  My intuition 
> tells me
>    >    >    that there is no way a memoized version of the generic 
> hash-equal would
>    >    >    pay off.  It seems we would have to flush on each call, or 
> never.  It
>    >    >    would only speed up index calculations of great depth, which is 
> only
>    >    >    useful in hash tables if your index is insufficiently random at 
> the
>    >    >    default depth of 3.  This does not appear the case, as #'equal 
> itself is
>    >    >    absent from the profiling report, implying that the hit rate to 
> the
>    >    >    index is good.
>    >    >
>    >    >    I suppose an 'equal hashtable could keep an 'eq hashtable 
> internally for
>    >    >    the life of the table.  That might be interesting.
>    >    >
>    >    >    In any case, I don't want to waste a lot of time reinventing some
>    >    >    wheel.  If you or any of the other hashtable experts have some 
> wisdom
>    >    >    here, I'd be most appreciative.
>    >    >
>    >    >    Take care,
>    >    >    --
>    >    >    Camm Maguire                                        
> address@hidden
>    >    >    
> ==========================================================================
>    >    >    "The earth is but one country, and mankind its citizens."  --  
> Baha'u'llah
>    >    >
>    >    >
>    >    > _______________________________________________
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>    >    > address@hidden
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>    >
>    >
>    >
>    >    --
>    >    Jared C. Davis <address@hidden>
>    >    11410 Windermere Meadows
>    >    Austin, TX 78759
>    >    http://www.cs.utexas.edu/users/jared/
>    >
>    >
>    >
>    >
>    >
>
>    --
>    Camm Maguire                                     address@hidden
>    ==========================================================================
>    "The earth is but one country, and mankind its citizens."  --  Baha'u'llah
>



-- 
Jared C. Davis <address@hidden>
11410 Windermere Meadows
Austin, TX 78759
http://www.cs.utexas.edu/users/jared/