Cargo Optimizer
Chemical tanker stowage planner for M/T X (IMO 9000001, IBC ship type 2, 12 cargo tanks).
No installation and no internet needed: open index.html in a browser.
Offline chemical tanker stowage planner and cargo optimiser: IBC Code ship type and segregation checks, filling limits, list and deadweight, with a C++ (WebAssembly) search engine.
Optimisation goals (in order of priority)
- Stow the maximum cargo (every tonne that doesn't fit is the heaviest penalty).
- Use the fewest tanks, and leave the least empty volume in the tanks used (best fit).
- No slack tanks: a tank filled below an adjustable threshold (default 65 %) is heavily penalised, so one tank at 70 % is chosen over two tanks at 35 %.
- List: the part that can be corrected with empty ballast on the opposite side is penalised lightly, anything beyond that heavily; a ballast suggestion is given for the correction.
- P/S pairs preferred, slop tanks as a last resort.
Hard constraints: one parcel per tank, a filling limit per parcel, no common bulkhead between incompatible parcels, locked tanks are never touched.
Algorithm: "minimal sufficient" tank subsets for each parcel (12 tanks → 4096 subsets, capacity DP) plus their P/S symmetric closures; the most constrained parcel goes first, branch & bound with a capacity lower bound. Typical run time 10–800 ms.
C++ engine (v2)
The stowage search and the scoring done at every step (P/S moment, list during loading/discharge, slack, empty volume) are written in C++ in engine/stowage.cpp. They are compiled to WebAssembly and embedded in js/engine-wasm.js, so the app still runs by opening index.html, without internet. The UI, physics (VCF, filling limit) and compatibility stay in JavaScript.
- Settings → Optimiser engine: C++ — deep search (default, twice as wide a search), C++ — standard search (exactly the same plan as JS, ~25–40× faster), JavaScript (the previous engine).
- If WebAssembly can't be loaded, the planner falls back to the JavaScript engine automatically and shows a warning.
- Consistency: the C++ engine follows the same order of operations as JS and is compiled with FMA off (
-ffp-contract=off); in standard search, JS, WebAssembly and the native build give bit-for-bit the same plan and score (tests/engine-parity.js).
- Native build (ship's computer, command line):
npm run build:engine -- --native → build/stowage (input/output format at the top of engine/stowage.cpp).
- After changing the engine:
npm run build:engine (needs clang + lld: sudo apt install clang lld). js/optimizer.js and engine/stowage.cpp are the same algorithm; a change to one must be made to the other too.
Calculations
- Density/VCF: petroleum products ASTM Table 54B, lube oil / base oil ASTM Table 54D (15 °C), chemicals and vegetable oils the product's expansion coefficient β. The method can be changed by hand in the form.
- Filling limit = min(98 % × ρ(max temperature on passage) / ρ(loading temperature), 98 % × 1.54 / ρ).
- Weight: in vacuum or in air (WCF −0.0011).
- Compatibility: USCG 46 CFR 150 Figure 1 reactive group chart (exception pairs are shown as warnings), plus heat-sensitive products next to heated cargo (styrene, VAM, acrylonitrile…).
- DWT: T/S/W load line zone chosen by hand, optional draft-restricted DWT.
Manual editing
- Click a tank → type %, m³ or tonnes; slider; step (0.5–100, t/m³/%); "Fill to limit", "Match pair", "Even out", "Empty".
- With Keep parcel totals on, a change in one tank is carried over to the other tanks of the same parcel, so the parcel total stays the same.
- Every cell in the tank table is editable; the parcel is picked from a drop-down.
- Drag a parcel onto a tank; drag a tank onto another tank to move or swap.
- Tank lock: Optimise leaves locked tanks alone. Adding a new parcel doesn't disturb the current plan (it only goes into empty tanks).
- DWT: if the nominations exceed the deadweight, Optimise warns and asks before scaling all parcels down proportionally (Cancel → full nomination, with a DWT overrun warning). The optimiser also takes the P/S imbalance of the current ballast into account.
- Undo / redo (Ctrl+Z / Ctrl+Y), autosave, save/open JSON, CSV, A4 landscape print (with signature blocks).
Themes
Chart (paper, default) · Bridge (dark) · Night (red, night vision) · Auto.
Tests
npm test # calculation / optimiser tests + C++/JS parity test (Node)
npm run test:ui # browser smoke test (installed Chrome, or CHROMIUM_PATH=/path/to/chromium)
Desktop version (Tauri)
npm run tauri build — dist-web/ is regenerated from index.html, css/ and js/ on every build (npm run build:web); don't edit it by hand.
The regulatory data is a planning aid; the ship's Certificate of Fitness, the current IBC Code Ch.17/18, the USCG chart and the charterer's/shipper's instructions take precedence.
