Re: [igraph] Memory management of igraph_vector_t in C

[Tamas Nepusz]

Hi,

For igraph vectors, one has to distinguish between their _actual_ size
(i.e. the number of elements they hold) and their _capacity_ (i.e. the
maximum number of elements that they can hold without having to
re-allocate the internal memory area that backs the vector). When you
call igraph_vector_init, you set the _actual_ size of the vector - so,
if you pass N as the vector size, the vector will have N
(uninitialized) real elements. What you probably need is to initialize
the vector with zero size and then call igraph_vector_reserve(), which
increases (or decreases) the _capacity_ of the vector while keeping
its size (length) intact.

T.

T.


On Wed, Sep 9, 2015 at 7:53 PM, Hadidi, Lars
<address@hidden> wrote:
> When using the igraph_vector_t type, it needs to be initialized with the
> function igraph_vector_init, which takes the amount of elements to be
> initialized as an argument. The documentation says, that the size of vectors
> will be handles automatically by increasing their size on demand, but not
> using free when they decrease, in order to keep performance. Therefore, some
> internal management must be done. My question is, if it is possible to
> overestimate the size of the vector on initialization and assigning elements
> less then the initialization size ? Will the internal management keep track
> of that, and will the algorithms perform correctly on such vectors. I try to
> avoid memory allocation inside the main loop of my program.
>
>
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