Re: senseless warning in octave-3.6.2

[Sergei Steshenko]

----- Original Message -----
> From: Sergei Steshenko <address@hidden>
> To: Francesco Potortì <address@hidden>
> Cc: c. <address@hidden>; Octave users list <address@hidden>
> Sent: Sunday, July 1, 2012 11:09 PM
> Subject: Re: senseless warning in octave-3.6.2
> 
> 
> 
> 
> 
> ----- Original Message -----
>>  From: Francesco Potortì <address@hidden>
>>  To: Sergei Steshenko <address@hidden>
>>  Cc: c. <address@hidden>; Octave users list 
> <address@hidden>
>>  Sent: Sunday, July 1, 2012 11:02 PM
>>  Subject: Re: senseless warning in octave-3.6.2
>> 
>>>  Here is a small test case:
>>> 
>>>  "
>>>  octave:1> foo = zeros(1, 1e6);
>>>  octave:2> bar = ones(1e6, 1);
>>>  octave:3> doo = foo + bar;
>>>  warning: operator +: automatic broadcasting operation applied
>>>  error: memory exhausted or requested size too large for range of 
>>  Octave's index type -- trying to return to prompt
>>>  octave:3> doo = foo' + bar;
>>>  octave:4>     
>>>  "
>>> 
>>>  which illustrates the problem
>>> 
>>>  Is it a bug or a feature ?
>> 
>>  This is a feature.  Excerpt from the 3.6 NEWS:
>> 
>>  ** Many of Octave's binary operators (.*, .^, +, -, ...) now perform
>>      automatic broadcasting for array operations which allows you to use
>>      operator notation instead of calling bsxfun or expanding arrays (and
>>      unnecessarily wasting memory) with repmat or similar idioms.  For
>>      example, to scale the columns of a matrix by the elements of a row
>>      vector, you may now write
>> 
>>        rv .* M
>> 
>>      In this expression, the number of elements of rv must match the
>>      number of columns of M.  The following operators are affected:
>> 
>>        plus      +  .+
>>        minus     -  .-
>>        times     .*
>>        rdivide   ./
>>        ldivide   .\
>>        power     .^  .**
>>        lt        <
>>        le        <=
>>        eq        ==
>>        gt        >
>>        ge        >=
>>        ne        !=  ~=
>>        and       &
>>        or        |
>>        atan2
>>        hypot
>>        max
>>        min
>>        mod
>>        rem
>>        xor
>> 
>>      additionally, since the A op= B assignment operators are equivalent
>>      to A = A op B, the following operators are also affected:
>> 
>>        +=  -=  .+=  .-=  .*=  ./=  .\=  .^=  .**=  &=  |=
>> 
>>      See the "Broadcasting" section in the new "Vectorization 
> and 
>>  Faster
>>      Code Execution" chapter of the manual for more details.
>> 
> 
> If it is a feature, why did it fail ? Is the expected behavior to create a 
> 1e6 x 
> 1e6 matrix ?
> 
> Thanks,
>   Sergei.
> 

A scaled down example:

"
octave:1> foo = zeros(1, 1e3);
octave:2> bar = ones(1e3, 1);
octave:3> doo = foo + bar;
warning: operator +: automatic broadcasting operation applied
octave:4> size(doo)
ans =

   1000   1000

octave:5> size(foo)
ans =

      1   1000

octave:6> size(bar)
ans =

   1000      1

octave:7>
"

- why the result is a matrix despite the fact that both operands of the '+' 
operator are vectors ?

Thanks,
  Sergei.






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