Add documentation on performance and work-around for sparse variable creation #2126
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docs/src/variables.md
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| @@ -387,6 +387,12 @@ JuMP.Containers.SparseAxisArray{VariableRef,1,Tuple{Int64}} with 2 entries: | |||
| [2] = x[2] | |||
| ``` | |||
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| Note that with many indices and large amount of sparcity, variable construction may take more time than expected, as JuMP is effectively iterating over all indices and evaluating the conditional for each combination. The recommended work-around in such cases is to work directly with a list of tuples. For example: | |||
docs/src/variables.md
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| ```jldoctest; setup=:(model=Model()) | ||
| S = [(1,1,1),(10,10,10)] | ||
| @variable(model, x[S]) |
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Could you make an example with both approach and then show that e.g. one has quadratic complexity and the other one has linear complexity? For instance with a condition i == j and n elements for i and j, it will be quadratic complexity vs linear complexity
docs/src/variables.md
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| @@ -387,6 +387,12 @@ JuMP.Containers.SparseAxisArray{VariableRef,1,Tuple{Int64}} with 2 entries: | |||
| [2] = x[2] | |||
| ``` | |||
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| Note that with many indices and large amount of sparcity, variable construction may take more time than expected, as JuMP is effectively iterating over all indices and evaluating the conditional for each combination. The recommended work-around in such cases is to work directly with a list of tuples. For example: | |||
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Please follow the 80-character limit used in the rest of the documentation.
docs/src/variables.md
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| @@ -387,6 +387,12 @@ JuMP.Containers.SparseAxisArray{VariableRef,1,Tuple{Int64}} with 2 entries: | |||
| [2] = x[2] | |||
| ``` | |||
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| Note that with many indices and large amount of sparcity, variable construction may take more time than expected, as JuMP is effectively iterating over all indices and evaluating the conditional for each combination. The recommended work-around in such cases is to work directly with a list of tuples. For example: | |||
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"is effectively iterating" is unnecessarily imprecise, just "iterates"
Codecov Report
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## master #2126 +/- ##
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Coverage 91.08% 91.08%
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Files 41 41
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Hits 3986 3986
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I don't want to merge this until we have a green light on the documentation build. |
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@hellemo can you rebase against master ? |
Add note on possible performance implications and suggested work-around following the discussion here:
https://discourse.julialang.org/t/working-efficiently-with-sparse-variables-in-jump/32240