relative to the same thing without the Val
On Wednesday, August 10, 2016 at 2:45:06 PM UTC-4, Jeffrey Sarnoff wrote:
>
> that slows it down by a factor of 5
>
> On Wednesday, August 10, 2016 at 2:37:25 PM UTC-4, Bill Hart wrote:
>>
>> How about compared with:
>>
>> ntuple(i -> a[i] + b[i], Val{N})
>>
>>
>> On 10 August 2016 at 20:32, Jeffrey Sarnoff <[email protected]> wrote:
>>
>>> Bill,
>>>
>>> Following Eric's note, I tried (with a,b equi-length tuples)
>>> function addTuples(a,b)
>>> ca = CartesianIndex(a)
>>> cb = CartesianIndex(b)
>>> return (ca+cb).I
>>> end
>>>
>>>
>>> for me, with 100 values it ran ~60% faster, and with 1000 values much
>>> much faster than
>>> ntuple(i -> a[i] + b[i], N)
>>>
>>>
>>>
>>> On Wednesday, August 10, 2016 at 11:06:46 AM UTC-4, Bill Hart wrote:
>>>>
>>>> This code seems to be (about 50%) faster than recursive functions:
>>>>
>>>> Base.:+{N}(a::NTuple{N}, b::NTuple{N}) = ntuple(i -> a[i] + b[i], N)
>>>>
>>>>
>>>> But this seems (about 50%) slower:
>>>>
>>>> ((a[i] + b[i] for i = 1:N)...)
>>>>
>>>>
>>>> Anyway, I can use the first method, until I find something faster. It's
>>>> definitely way more convenient. Thanks.
>>>>
>>>> Bill.
>>>>
>>>>
>>>>
>>>> On 10 August 2016 at 16:56, Erik Schnetter <[email protected]> wrote:
>>>>
>>>>> The built-in type `CartesianIndex` supports adding and subtracting,
>>>>> and presumably also multiplication. It is implemented very efficiently,
>>>>> based on tuples.
>>>>>
>>>>> Otherwise, to generate efficient code, you might have to make use of
>>>>> "generated functions". These are similar to macros, but they know about
>>>>> the
>>>>> types upon which they act, and thus know the value of `N`. This is a bit
>>>>> low-level, so I'd use this only if (a) there is not other package
>>>>> available, and (b) you have examined Julia's performance and found it
>>>>> lacking.
>>>>>
>>>>> I would avoid overloading operators for `NTuple`, and instead us a new
>>>>> immutable type, since overloading operations for Julia's tuples can have
>>>>> unintended side effects.
>>>>>
>>>>> -erik
>>>>>
>>>>>
>>>>> On Wed, Aug 10, 2016 at 9:57 AM, 'Bill Hart' via julia-users <
>>>>> [email protected]> wrote:
>>>>>
>>>>>> Does anyone know an efficient way to add NTuples in Julia?
>>>>>>
>>>>>> I can do it using recursive functions, but for various reasons this
>>>>>> is not efficient in my context. I really miss something like tuple(a[i]
>>>>>> +
>>>>>> b[i] for i in 1:N) to create the resulting tuple all in one go (here a
>>>>>> and
>>>>>> b would be tuples).
>>>>>>
>>>>>> The compiler doesn't do badly with recursive functions for handling
>>>>>> tuples in very straightforward situations, but for example, if I want to
>>>>>> create an immutable type based on a tuple the compiler doesn't seem to
>>>>>> be
>>>>>> able to handle the necessary optimisations. At least, that is what I
>>>>>> infer
>>>>>> from the timings. Consider
>>>>>>
>>>>>> immutable bill{N}
>>>>>> d::NTuple{N, Int}
>>>>>> end
>>>>>>
>>>>>> and I want to add two bill's together. If I have to add the tuples
>>>>>> themselves using recursive functions, then I no longer seem to be able
>>>>>> to
>>>>>> do something like:
>>>>>>
>>>>>> A[i] = B[i] + C[i] efficiently, where A, B and C are arrays whose
>>>>>> elements are of type bill.
>>>>>>
>>>>>> I know how to handle tuples via arrays, but for efficiency reasons I
>>>>>> certainly don't want to do that, e.g. tuple([a[i] + b[i] for i in
>>>>>> 1:N]...).
>>>>>>
>>>>>> Bill.
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>> --
>>>>> Erik Schnetter <[email protected]>
>>>>> http://www.perimeterinstitute.ca/personal/eschnetter/
>>>>>
>>>>
>>>>
>>
