I’m trying to solve a simple linear system. However, it seems like the preallocated versions of any IterativeSolvers.jl functions are either much slower or allocating more memory. Here’s the example: using IterativeSolvers using LinearMaps function SecondOrderCentralDiffmul!(C, B) C[1] = -2B[…

This is actually not related to IterativeSolvers, but to BenchmarkTools subtleties, mostly because it runs the function several times to get a better estimate of the time. First, as a rule, you should always interpolate global variables when benchmarking. Furthermore, running the mutating version …

@gdalle awesome! One last thing is that I still don’t understand why the mutating gmres! is allocating the same amount of memory as non-mutating version?

I would also note that mutating gmres! allocates memory even without using LinearMaps. julia> using IterativeSolvers, BenchmarkTools julia> function f!(x, A, b, n_runs=1) for i in 1:n_runs x .= 0 gmres!(x, A, b) end return nothing end f! (gen…

[image] leespen1: Still, it would be nice to have a ‘cached’ option, just to be sure that memory allocation isn’t significantly affecting performance. I definitely agree. The fact that we can’t provide this option makes it so that for many specific cases the user will have to write their own …

Actually I think there is an advanced interface where you can avoid repeated allocation. See here: The iterator approach · IterativeSolvers.jl

@abraemer wow completely missed this section. Good catch

You’re right, thanks! I would note that it’s not immediately obvious how to avoid repeated allocation with gmres, since the user has to repeat some of the initialization process when setting a new value for b. But some of the solvers, like jacobi, are much easier (just set a new b and do the iterat…

That seems like useful information that could be preserved. I suggest opening a pull request to IterativeSolvers.jl to put this into the documentation as an example usage of the iterator interface :slight_smile:

IterativeSolvers.jl not working as expected with mutating and allocation

General Usage

leespen1 March 5, 2024, 9:49pm 10

Thanks, I’m working on it now.

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IterativeSolvers.jl not working as expected with mutating and allocation

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