Write a version in Python that can infer 40 from the inputs then maybe we
can talk about declarative. I have no idea what you mean by "cheating" and
even less of an idea what you mean by "nice."
On Saturday, November 12, 2011, Jules <julesjac...@gmail.com> wrote:
> The time difference is largely due to using the product library
> function instead of for comprehensions and the fact that the cKanren
> version cheats by hardcoding part of the solution, and hardcoding an
> extra constraint alldiff(a,b,c,d). The following code takes ~12ms with
> PyPy on my computer:
>
> def valid(a,b,c,d):
> weights = set(w*a+x*b+y*c+z*d for w in [-1,0,1]
> for x in [-1,0,1]
> for y in [-1,0,1]
> for z in [-1,0,1])
> return weights >= set(range(1,41))
>
>
> ws = [(a,b,c,d) for a in range(1,40)
> for b in range(1,40) if a <= b
> for c in range(1,40) if b <= c
> for d in range(1,40) if c <= d
> if a+b+c+d == 40 and valid(a,b,c,d)]
>
> If you cheat with `for a in [1]` instead of `for a in range(1,40)` and
> changing the <= to < (the same cheat as the alldiff), then the
> execution time drops to 2ms.
>
> Since we don't seem to be going to agree on the definition of
> declarative, lets use another word: nice. Lets define niceness as
> understandability and closeness to mathematical specification. I agree
> that the matches definition is already nice: it handles the
> constraints and symmetry breaking nicely (better than the Python
> version if you ignore syntactic issues e.g. a+b+c+d=40 is more
> convoluted). But the checko and subchecko leave a lot to be desired.
> So my question is: can the cKanren version be improved so that it also
> becomes nice?
>
> Jules
>
> On 12 nov, 07:16, David Nolen <dnolen.li...@gmail.com> wrote:
>> Also note that even given all this generality over the Python code - the
>> earlier Python implementation takes ~300ms and this implementation takes
>>
>> >900ms on my machine.
>>
>> Quite a bit slower than ~12ms. Inferring 40 takes even less time of
course
>> - ~8ms.
>>
>> But really the execution time is just icing on the declarative cake ;)
>>
>> David
>>
>>
>>
>>
>>
>>
>>
>> On Fri, Nov 11, 2011 at 8:09 PM, Jules <julesjac...@gmail.com> wrote:
>> > Here is a new program. Perhaps you would consider this declarative:
>>
>> > def valid(a,b,c,d):
>> > weights = set(w*a+x*b+y*c+z*d for (w,x,y,z) in
>> > product([-1,0,1],repeat=4))
>> > return weights >= set(range(1,41))
>>
>> > ws = [(a,b,c,d) for (a,b,c,d) in product(range(1,41),repeat=4)
>> > if a <= b <= c <= d and a+b+c+d == 40 and
>> > valid(a,b,c,d)]
>>
>> > On 12 nov, 01:48, Jules <julesjac...@gmail.com> wrote:
>> > > Are we reading the same cKanren code? I'll give you that the matches
>> > > definition is declarative, but then read checko and subchecko. They
>> > > are all about (recursive) control flow. Where does the specification
>> > > say anything remotely close to the checko and subchecko relations? In
>> > > contrast to this, the Python set comprehensions have minimal control
>> > > flow. Yeah, the standard Python implementation has a certain order of
>> > > executing the comprehensions, but so does the cKanren implementation
>> > > when executing the predicates. My Python program doesn't depend on
>> > > this order: it just uses declarative descriptions of sets as set
>> > > comprehensions.
>>
>> > > Just being written in cKanren doesn't make a program declarative. If
>> > > you write a C interpreter in cKanren and then write your actual
>> > > program in a literal string, that doesn't magically make the program
>> > > declarative even though it is a cKanren program. Similarly, checko
and
>> > > subchecko don't describe the problem in a declarative way. Compare
>> > > this with the Python valid() function: the set of possible weights
you
>> > > can make has to be a superset of {1..40}. Again, declarativeness is a
>> > > property of programs, not languages. Some languages make writing
>> > > declarative programs easier, of course. cKanren is supposed to be
such
>> > > a language, so it would be neat to see a more declarative cKanren
>> > > program for this problem.
>>
>> > > Also, I don't see how "one stone should weigh 1lbs" is part of the
>> > > specification. Now, it is true that the answer happens to have one
>> > > stone equal to 1, but how is that part of or trivially follows from
>> > > the specification? We might as well hard-code the whole solution.
>>
>> > > Jules
>>
>> > > On 12 nov, 00:49, Timothy Baldridge <tbaldri...@gmail.com> wrote:
>>
>> > > > > My Python code is much more declarative than the given
>> > > > > cKanren code in that regard. Just compare:
>> >http://dosync.posterous.com/another-taste-of-ckanren
>>
>> > > > I don't think you understand what declarative programming is at its
>> > > > core. Declarative programming
>>
>> > > > To borrow from the ever-present wikipedia:
>> > > > "declarative programming is a programming paradigm that expresses
the
>> > > > logic of a computation without describing its control flow.[1] Many
>> > > > languages applying this style attempt to minimize or eliminate side
>> > > > effects by describing what the program should accomplish, rather
than
>> > > > describing how to go about accomplishing it.[2] This is in contrast
>> > > > with imperative programming, which requires an explicitly provided
>> > > > algorithm." (see: Declarative Programming)
>>
>> > > > This is where the cKanren code succeeds where the Python code
fails.
>> > > > The Python code is all algorithm, and no facts. While the cKanren
code
>> > > > is a direct implementation of the facts about the problem: one
stone
>> > > > must be 1lb all stones should equal 40lb, etc. The cKanren code
leaves
>> > > > the interpretation of these facts up to the logic engine, while the
>> > > > Python code sets strict guidelines that the compiler must follow.
If,
>> > > > for instance, i
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