[R] R-memory: clearing memory within a function?

[Henrik Bengtsson]

See blog post 'Speed trick: Assigning large object NULL is much faster
than using rm()!':

  http://www.jottr.org/2013/05/speed-trick-assigning-large-object-null.html

/Henrik

On Tue, Jun 3, 2014 at 5:35 PM, Ista Zahn <istazahn at gmail.com> wrote:
> Hi Frank,
>
> I don't think it is possible to state a general rule about which will
> be faster. For example this
>
> system.time({
>     for(i in 1:10000) {
>         x <- matrix(rnorm(10), ncol = 10)
>         y <- mean(x)
>         #rm(x)
>         z <- matrix(runif(10), ncol = 100)
>         #rm(z)
>     }
> })
>
> gets a lot slower if I uncomment the "rm()" lines, but this
>
> system.time({
>     for(i in 1:5) {
>         x <- matrix(rnorm(10000000), ncol = 10)
>         y <- mean(x)
>         rm(x)
>         z <- matrix(runif(10000000), ncol = 100)
>         rm(z)
>     }
> })
>
> is slightly faster than it would be without the rm() lines. I think
> you'll have to run a smaller version of the simulation both ways and
> see which is faster.
>
> Best,
> Ista
>
> On Tue, Jun 3, 2014 at 10:05 AM, Frank van Berkum
> <frankieboytje at hotmail.com> wrote:
>> Dear R-users,
>>
>> I'm working on a project in which many simulations have to be performed within functions. The simulations are quite time consuming. I thought that in general an empty memory is better for speed performance than a full memory.
>>
>> If I call a function which performs simulations within the function, than the memory will temporarily increase (while the function is executed and objects are created within the function), but as soon as the function is finished, temporarily objects are flushed. It seems as if it might be beneficial for speed performance to clear objects from the memory within the function if they are no longer needed in the remainder of the function. Does anyone know whether this is actually the case?
>>
>> Thanks in advance!
>>
>> Frank
>>         [[alternative HTML version deleted]]
>>
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>
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