[gmx-developers] size of out->f array

Mark Abraham mark.j.abraham at gmail.com
Tue Jun 30 22:50:15 CEST 2015


Hi,

Yes, that's enough for safety.

Mark

On Tue, Jun 30, 2015 at 10:46 PM Sikandar Mashayak <mashayak at votca.org>
wrote:

> Thanks Mark,
>
> In that case, if I were to copy the data from out->f to another array (say
> real *ftmp) then the size of the ftmp must be nbat->nalloc*fstride.
>
> Thanks,
> Sikandar
>
> On Tue, Jun 30, 2015 at 2:22 PM, Mark Abraham <mark.j.abraham at gmail.com>
> wrote:
>
>> Hi,
>>
>> This is "just" like std::vector. There's a number of elements in the
>> array and a size to the storage. Reallocation is something you want to
>> avoid (particularly for high-performance multi-threaded code), so you
>> over-allocate the size when you first know the number, and hope you will
>> never need to re-allocate.
>>
>> Mark
>>
>> On Tue, Jun 30, 2015 at 10:03 PM Sikandar Mashayak <mashayak at votca.org>
>> wrote:
>>
>>> Hi,
>>>
>>> I am a bit confused about length/size of the out->f , x, and q arrays.
>>> Looking at the data structures in the nbnxn_pairlist.h, there are two size
>>> related variables, natoms and nalloc. And in nbnxn_atomdata.c, when f, x,
>>> and q arrays are reallocated they are passed nalloc*stride size value. Does
>>> that mean the actual size is nalloc*stride or natoms*stride? Also, I
>>> noticed nalloc and natoms may not be the same.
>>>
>>> Thanks,
>>> Sikandar
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>>
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