No big deal, just now noticed it, is all. FWIW, I like the comprehension
order better (inner = faster). Although I also see François' point about
the for loop nesting.
Thanks,
--Peter
On Friday, May 16, 2014 2:10:19 PM UTC-7, Stefan Karpinski wrote:
>
> It's less about the array ordering and more about the fact that
> mathematically the row index comes before the column index and doing it the
> other way would be very confusing. It's a shame these don't match, but
> there's not much to do about it.
>
> On May 16, 2014, at 4:57 PM, francoi...@gmail.com <javascript:> wrote:
>
> I am very new to Julia, but here is my guess :
> - for i = , j =
> should be the same as
> for i =
> for j =
> It would be awkward to have something else.
> - For comprehensions, the order is the other way around because matrices
> are stored in Julia in column order as in Fortran (and maybe Matlab) as
> opposed to C. Therefore, ordering the comprehension that way make the
> filling of the array cache-friendly.
>
> François
>
> On Friday, May 16, 2014 10:52:22 PM UTC+2, Peter Simon wrote:
>>
>> Comprehensions and for loops do not perform nested looping in the same
>> order:
>>
>> julia> [begin println((i,j)); (i,j) end for i = 1:3, j = 1:4]
>> (1,1)
>> (2,1)
>> (3,1)
>> (1,2)
>> (2,2)
>> (3,2)
>> (1,3)
>> (2,3)
>> (3,3)
>> (1,4)
>> (2,4)
>> (3,4)
>> 3x4 Array{(Int64,Int64),2}:
>> (1,1) (1,2) (1,3) (1,4)
>> (2,1) (2,2) (2,3) (2,4)
>> (3,1) (3,2) (3,3) (3,4)
>>
>>
>> julia> for i = 1:3, j=1:4
>> println((i,j))
>> end
>> (1,1)
>> (1,2)
>> (1,3)
>> (1,4)
>> (2,1)
>> (2,2)
>> (2,3)
>> (2,4)
>> (3,1)
>> (3,2)
>> (3,3)
>> (3,4)
>>
>>
>>
>> Just wondering what the rationale is for this difference.
>>
>> --Peter
>>
>
