CacheVariables.jl

A lightweight way to save outputs from (expensive) computations.

Function form

The function form saves the output of running a function and can be used with the do...end syntax.

cache("test.bson") do
  a = "a very time-consuming quantity to compute"
  b = "a very long simulation to run"
  return (; a = a, b = b)
end

The first time this runs, it saves the output in a BSON file called test.bson. Subsequent runs load the saved output from the file test.bson rather than re-running the potentially time-consuming computations! Especially handy for long simulations.

An example of the output:

julia> using CacheVariables

julia> cache("test.bson") do
         a = "a very time-consuming quantity to compute"
         b = "a very long simulation to run"
         return (; a = a, b = b)
       end
[ Info: Saving to test.bson
(a = "a very time-consuming quantity to compute", b = "a very long simulation to run")

julia> cache("test.bson") do
         a = "a very time-consuming quantity to compute"
         b = "a very long simulation to run"
         return (; a = a, b = b)
       end
[ Info: Loading from test.bson
(a = "a very time-consuming quantity to compute", b = "a very long simulation to run")

Macro form

The macro form looks at the code to determine what variables to save.

@cache "test.bson" begin
  a = "a very time-consuming quantity to compute"
  b = "a very long simulation to run"
  100
end

The first time this block runs, it identifies the variables a and b and saves them (in addition to the final output 100 that is saved as ans) in a BSON file called test.bson. Subsequent runs load the saved values from the file test.bson rather than re-running the potentially time-consuming computations! Especially handy for long simulations.

An example of the output:

julia> using CacheVariables

julia> @cache "test.bson" begin
         a = "a very time-consuming quantity to compute"
         b = "a very long simulation to run"
         100
       end
┌ Info: Saving to test.bson
│ a
└ b
100

julia> @cache "test.bson" begin
         a = "a very time-consuming quantity to compute"
         b = "a very long simulation to run"
         100
       end
┌ Info: Loading from test.bson
│ a
└ b
100

An optional overwrite flag (default is false) at the end tells the macro to always save, even when a file with the given name already exists.

julia> @cache "test.bson" begin
         a = "a very time-consuming quantity to compute"
         b = "a very long simulation to run"
         100
       end false
┌ Info: Loading from test.bson
│ a
└ b
100

julia> @cache "test.bson" begin
         a = "a very time-consuming quantity to compute"
         b = "a very long simulation to run"
         100
       end true
┌ Info: Overwriting test.bson
│ a
└ b
100

See also a similar package: Memoization.jl

Caveat: The variable name ans is used for storing the final output (100 in the above examples), so it is best to avoid using this as a variable name.