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set_input for one period leaves the variable's cached sum or twelfth over an overlapping period in place

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#579 0 comments 0 reactions 0 assignees View on GitHub

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@MaxGhenis is already working on this.

Since Oct 6, 2026.

  • #593 by @MaxGhenis — open

Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
68/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
python
Domain
backend, performance

Research direction

Start by tracing Holder.set_input and Holder._set, then follow Simulation.calculate_add, calculate_divide, and _calculate to understand how overlapping periods and branches are cached. Reproduce the four calculation sequences in the issue; done means setting an input for its own period no longer leaves stale sums or twelfths while existing cache behavior remains intact.

Written by the indexing model from the issue text.

Description

set_input for one of a variable's own periods (one month of a monthly variable, one year of a yearly one) replaces the value stored for that period, but leaves in place what the simulation had calculated from it for the same variable at periods of another size: the sum calculate caches for a monthly flow over a year, and the twelfth it caches for a yearly flow at a month. A later calculate returns the cached value, so the result depends on whether the longer (or shorter) period was read before the input was set.

Executed on master b78b0ba9 (two people, formula-less float variables, auto_carry_over_input_variables off):

Steps Result
calculate("flow_m", "2013"); set_input("flow_m", "2013-05", [50, 0]); calculate("flow_m", "2013") [0, 0]
set_input("flow_m", "2013-05", [50, 0]); calculate("flow_m", "2013") [50, 0]
calculate("flow_y", "2013-05"); set_input("flow_y", "2013", [1200, 0]); calculate("flow_y", "2013-05") [0, 0]
set_input("flow_y", "2013", [1200, 0]); calculate("flow_y", "2013-05") [100, 0]

flow_m is a monthly float variable and flow_y a yearly one, both with no formula.

Where it comes from: Simulation.calculate_add stores the sum at the requested period and calculate_divide stores the twelfth at the month (holder.put_in_cache(result, period, self.branch_name)), and _calculate returns a stored value for the requested period before anything else. Holder.set_input with a period of the variable's own unit calls Holder._set for that period only.

The inputs set over a longer period through set_input_divide_by_period and set_input_dispatch_by_period have the same problem and more; the PR for those helpers drops the variable's calculated sums and twelfths that overlap the input period. This issue is the remaining path: an input for the variable's own period. The same rule would fix it (an input drops the values calculated for that variable at overlapping periods of another size, on the branch it is stored under and the branches read through it), applied in Holder.set_input.

Not covered by #571 (which keeps the cache for a flow read over a period of another unit), #566/#576 (the fast cache, not holder storage) or #560 (other variables calculated from the input, on branches).

Dominant language
Python
Stars
22
Forks
30
Avg merge
2d 21h
Merged PRs (30d)
24

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