That overhead seems constant, beyond a single temporary. So I dont suppose there is that much to be worried about, unless you are using many small arrays.
julia> 800-sizeof(rand(2)) 784 julia> 944-sizeof(rand(20)) 784 On Tuesday, 29 April 2014 10:40:10 UTC+1, Carlos Becker wrote: > > Besides Julia internals, I suppose there is memory overhead in terms of > the structure holding the array itself (when temporaries are created). > I suppose an array isn't just the size in bytes of the data it holds, but > also information about its size/type/etc. Though I doubt that would add up > to 800 bytes, it could explain part of it. > > I wonder if there is a way within julia to know the 'real' size of a julia > object. > > El martes, 29 de abril de 2014 11:32:21 UTC+2, Carlos Becker escribió: >> >> I just saw another part of your message, I am wondering also why memory >> consumption is so high. >> >> El martes, 29 de abril de 2014 11:31:09 UTC+2, Carlos Becker escribió: >>> >>> This is likely to be because Julia is creating temporaries. This is >>> probably why you get increasing memory usage when increasing array size. >>> >>> This is a long topic, that will have to be solved (hopefully soon), I >>> had a previous question related to something similar here: >>> https://groups.google.com/d/topic/julia-users/Pbrm9Nn9fWc/discussion >>> >>> >>> El martes, 29 de abril de 2014 08:05:17 UTC+2, John Aslanides escribió: >>>> >>>> I'm aware that evaluating a vectorized operation (say, an elementwise >>>> product of two arrays) will result in the allocation of a temporary array. >>>> I'm surprised, though, at just how much memory this seems to consume in >>>> practice -- unless there's something I'm not understanding. Here is an >>>> extreme example: >>>> >>>> julia> a = rand(2); b = rand(2); >>>> >>>> julia> @time a .*= b; >>>> elapsed time: 0.505942281 seconds (11612212 bytes allocated) >>>> >>>> julia> @time a .*= b; >>>> elapsed time: 1.4177e-5 seconds (800 bytes allocated) >>>> >>>> julia> @time a .*= b; >>>> elapsed time: 2.5334e-5 seconds (800 bytes allocated) >>>> >>>> 800 bytes seems like a lot of overhead given that a and b are both only >>>> 16 bytes each. Of course, this overhead (whatever it is) becomes >>>> comparatively less significant as we move to larger arrays, but it's still >>>> sizeable: >>>> >>>> julia> a = rand(20); b = rand(20); >>>> >>>> julia> @time a.*= b; >>>> elapsed time: 1.4162e-5 seconds (944 bytes allocated) >>>> >>>> julia> @time a.*= b; >>>> elapsed time: 2.3754e-5 seconds (944 bytes allocated) >>>> >>>> Can someone explain what's going on here? >>>> >>>
