Skip to content

Cache Calculator (cache://)

The cache:// calculator does not run anything. It looks in one or more existing result directories for a case whose input files hash identically to the current case and, if it finds one with valid outputs, copies those results in — skipping the computation.

Put it first in a calculator list so real calculators only run on cache misses.

URI Syntax

cache://path/to/results

calculators = "cache://previous_run"

calculators = ["cache://run1", "cache://archive/results"]      # several caches

calculators = ["cache://archive/2024-*/results"]               # glob patterns

calculators = [
    "cache://previous_results",   # try cache first
    "sh://bash calculate.sh",     # compute on miss
]

How It Works

  1. Compute the MD5 hash of every input file for the current case.
  2. Search the cache directories for a .fz_hash file whose entries all match.
  3. Check that the cached outputs are non-None.
  4. On a hit, copy the cached result files in and mark the case done; on a miss, fall through to the next calculator.

Matching is by .fz_hash content, not directory name — so a cache written with any case_naming scheme (path / hash / index) still matches.

.fz_hash
a1b2c3d4e5f6...  input.txt
f6e5d4c3b2a1...  config.dat

Note

The cache keys on input files only, not on the calculator command. Editing your calculation script but not the inputs will still produce a cache hit — use a fresh results_dir without cache:// to force recomputation.

Common Uses

fz.fzr("input.txt", {"p": range(100)}, model, "sh://bash calc.sh", "run1")
# ... Ctrl+C after 50 cases ...
fz.fzr("input.txt", {"p": range(100)}, model,
       ["cache://run1", "sh://bash calc.sh"], "run1_resumed")

fz.fzr("input.txt", {"t": [100, 200, 300]}, model, "sh://bash calc.sh", "study1")
fz.fzr("input.txt", {"t": [100, 200, 300, 400, 500]}, model,
       ["cache://study1", "sh://bash calc.sh"], "study2")   # reuses 3, runs 2

calculators = [
    "cache://latest_run",
    "cache://archive/2024-*",
    "cache://archive/*/*",
    "sh://bash calc.sh",
]

See Also