EVEShip.fit's Dogma Engine

This library calculates accurately statistics of an EVE Online ship fit.

The input are several data-files provided by EVE Online, together with a ship fit. The output are all the Dogma attributes of the ship, its items and the character.

Implementation

This Dogma engine implements a multi-pass approach.

• pass 1: collect all the Dogma attributes of the hull and modules.
• pass 2: collect all the Dogma effects of the hull and modules.
• pass 3: apply all the Dogma effects to the hull/modules, calculating the actual Dogma attribute values.
• pass 4: augment the Dogma attributes with EVEShip.fit specific attributes, that are too complex for the Dogma itself to handle.

Input and output

calculate takes a fit and options, and returns a calculation. All identifiers are those from the SDE.

Fit

• name (optional): name of the fit.
• ship: the ship being fitted.
  • type_id: its type.
  • mode (optional): type ID of the active mode, for ships that have modes. Whether the mode belongs to the ship is not checked.
• items: everything fitted or carried. Each item has:
  • type_id: its type.
  • slot: where the item is.
    • type: high, medium, low, rig, subsystem, service, fighter_tube, fighter_bay, implant, booster, drone_bay or cargo.
    • index: position within that slot type, starting at 0 (implant and booster starting at 1). Absent for fighter_bay, drone_bay and cargo.
  • quantity (optional, default 1): stack size for drones, fighters and cargo. For fighters in a tube, the squadron size.
  • state: requested state; offline, online, active or overload.
  • charge (optional): the loaded charge, as type_id.
  • mutation (optional): for mutated items (Abyssal modules, mutated drones, ...).
    • base: type ID of the item before it was mutated.
    • attributes: the rolled value per attribute ID.
  • fighter_abilities (optional): the abilities a fighter uses, as effect IDs. Absent means the fighter's default abilities.
  • booster_side_effects (optional): the side effects a booster rolled, as effect IDs. Absent means none.
  • spool (optional): for modules whose bonus grows every cycle, how far it has spooled. Only per-second stats use it; volley is always unspooled. Absent means fully spooled.
    • multiplier_bonus: the bonus reached so far; 0.0 is unspooled, 2.125 is +212.5%.
• character (optional):
  • skills: level (0 to 5) per skill type ID. A missing skill gives no bonuses.
  • security_status (optional, default 0.0): the pilot's security status, -10.0 to 5.0.
• environment (optional): where the fit is.
  • damage_profile (optional, default 0.25 each): incoming damage for effective hitpoints, as em, explosive, kinetic and thermal (relative to each other).
  • security (optional, default high_sec): high_sec, low_sec, null_sec or wormhole.
  • reactive_armor (optional, default do_not_adapt): what a Reactive Armor Hardener shifts its resistances towards. do_not_adapt leaves them where EVE shows them, damage_profile shifts towards damage_profile, and {"profile": {..}} shifts towards a profile of its own, written the same way as damage_profile.
• incoming (optional): what effects and buffs to apply that come from outside the ship. A calculation reports the same shape as outgoing: feed one fit's result into another's incoming links them up.
  • buffs (optional, default none): buffs to apply, like the ones a command burst hands out.
    • id: which buff, as dbuffCollections in the SDE numbers them.
    • value: how strong it is, in whatever the buff's operation reads.
  • effects (optional, default none): effects aimed at the fit, like a stasis webifier.
    • type_id: the type the effect belongs to; its category decides the stacking penalty.
    • effect_id: which effect, as dogmaEffects in the SDE numbers them.
    • attributes: the value per attribute ID the effect reads, worked out by the fit that aimed it.

Options

• sources (optional, default false): report per attribute what its value was calculated from. Leave it off unless you show it; it makes the calculation several times bigger.

Calculation

• ship: result for the ship.
• mode: result for the mode; absent when the fit has no mode.
• items: one result per item of the fit, in the same order.
• character: result for the character.
• buffs: the buffs that landed, ordered by id. Those of incoming, plus the ones the fit's own bursts hand out: a fleet boost reaches the ship running it. What is missing lost to another source of the same buff, or the SDE has no such buff.
  • id: which buff, as dbuffCollections in the SDE numbers them.
  • value: how strong it is, in whatever the buff's operation reads.
• outgoing: what the fit hands to other fits, in the shape incoming takes.

Each result has:

• attributes: per attribute ID, its base value before effects and its final value. With the sources option, also sources: every modifier on it, in the order they were applied. Each has:

  • from: where it comes from; type is ship, mode, character, item or charge (with the index into items), projected (with the index into incoming.effects), skill (with its type_id) or buff (with its id).
  • effect_id: the effect that holds the modifier; null for a buff, which has none.
  • source_attribute_id: the attribute on the source that holds value; null for a buff, which carries its own strength.
  • operator: pre_assign, pre_mul, pre_div, mod_add, mod_sub, post_mul, post_div, post_percent or post_assign.
  • value: the value of the modifying attribute, or the strength of the buff.
  • quantity: how many times it counts. A stacking penalised stack is listed once per item instead.
  • penalty: the stacking penalty factor it got, or null if not penalised.
  • applied: false when the source's state is too low for the effect.

  How much each source added is not reported: multiplications compound and stacking penalties depend on order, so there is no single answer.

• state: the state the item reached, which can be lower than requested.

• max_state: the highest state the item can reach.

• charge: result for its charge, if it has one.

EVEShip.fit's specific attributes

Pass 4 create Dogma attributes that do not exist in-game, but are rather complicated to calculate. To make rendering a fit easier, these are calculated by this library, and presented as new Dogma attributes.

Their identifier is always a negative value, to visually separate them. What additional attributes exist are defined in EVEShipFit/sde-patched repository.

Validation

validate() checks if the fit violates any rules that would prevent you from flying it in-game. It returns the violations, grouped by the kind of rule and, within a kind, in the order of items. An empty list means the fit breaks no rules.

Each violation has:

• target: what the rule is about.
  • ship, for what the ship carries as a whole.
  • item, with the index into items.
  • charge, with the index into items of the item holding it.
• rule: the rule, and the values that failed it. type says which:
  • resource: resource ran out, used of available. One of cpu, powergrid, calibration, drone_bay, drone_bandwidth, launched_drones, fighter_bay, fighter_tubes, light_fighter_tubes, support_fighter_tubes, heavy_fighter_tubes, cargo_bay or charge_capacity.
  • slots: more items in the slot rack than the ship has, used of available. One of high, medium, low, rig, subsystem, service, turret or launcher; the last two are hardpoints a weapon takes on top of its slot.
  • wrong_slot: the item belongs in the expected rack.
  • slot_taken: another item of the fit is in this slot too.
  • wrong_slot_index: an implant or booster outside the slot it occupies, which is expected.
  • subsystem_taken: another subsystem covers the same part of the ship.
  • skill: the character is missing type_id, or has it at level where the item asks for required.
  • rig_size: a rig of size item where the ship takes another.
  • ship_restricted: the item cannot go on this ship at all.
  • capital_item: a capital item on a ship that is not a capital.
  • max_group: used of group_id are limit (fitted, online or active), where allowed may be. This is what keeps a second propulsion module from running: an afterburner and a microwarpdrive share a group.
  • max_type: used of type_id are fitted, where allowed may be.
  • charge_group: a charge of a group the module does not take.
  • charge_size: a charge of size charge where the module takes another.

Usage

The engine is published for Rust, Javascript and Python; all three calculate the same way. Each hands over sde.dat once, and every lookup after that happens inside Rust. An EFT import matches the English names in sde.dat; hand over names.dat too to also match the other languages EVE supports.

How each package is built is explained under Integration.

Rust

The crate is published on crates.io as esf-dogma-engine. esf-data reads sde.dat.

cargo add esf-dogma-engine esf-data

use esf_data::{InfoSde, Sde};
use esf_dogma_engine::{Fit, Options, beacon, calculate, validate};

let bytes = std::fs::read("sde.dat")?;
let sde = Sde::new(&bytes)?;
let info = InfoSde::new(&sde);

let fit: Fit = serde_json::from_str(
    r#"{
        "ship": {"type_id": 587},
        "items": [
            {
                "type_id": 2873,
                "slot": {"type": "high", "index": 0},
                "state": "active",
                "charge": {"type_id": 185}
            }
        ],
        "character": {"skills": {"3300": 5}}
    }"#,
)?;

let calculation = calculate(&info, &fit, &Options::default());
// Or if you want to know the source of the effects:
let with_sources = calculate(&info, &fit, &Options { sources: true, ..Default::default() });
// Or if you have a beacon in space (like wormhole effects):
let with_beacon = calculate(&info, &Fit { incoming: beacon(&info, beacon_type_id), ..fit }, &Options::default());

// What EVE would not let you fly:
let violations = validate(&info, &fit, &calculation);

Javascript (WebAssembly)

The WebAssembly variant is published on npm as @eveshipfit/dogma-engine. @eveshipfit/sde ships sde.dat in its dist folder; serve or bundle that file.

The package is built for bundlers (Vite, webpack 5, ...), which load the .wasm themselves.

npm install @eveshipfit/dogma-engine @eveshipfit/sde

import {
  init,
  load_sde,
  load_eft,
  save_eft,
  calculate,
  validate,
  beacon,
} from "@eveshipfit/dogma-engine";

init();

const sde = await fetch("/sde.dat").then((response) => response.arrayBuffer());
const buildNumber = load_sde(new Uint8Array(sde));
const fit = {
  ship: { type_id: 587 },
  items: [{ type_id: 2873, slot: { type: "high", index: 0 }, state: "active", charge: { type_id: 185 } }],
  character: { skills: { 3300: 5 } },
};

const calculation = calculate(fit);
/* Or if you want to know the source of the effects: */
const withSources = calculate(fit, { sources: true });
/* Or if you have a beacon in space (like wormhole effects): */
const withBeacon = calculate({ ...fit, incoming: beacon(beaconTypeId) });
/* Or if you have an EFT, the text format EVE copies a fit to the clipboard in: */
const imported = calculate(load_eft("[Rifter, My Rifter]\n200mm AutoCannon I"));
/* And to write a fit back out as EFT: */
const eft = save_eft(fit);

/* What EVE would not let you fly; it calculates the fit itself: */
const violations = validate(fit);

Python

The Python variant is published on PyPI as eveshipfit-dogma-engine. The sde extra brings in eveshipfit-sde, which ships sde.dat.

pip install eveshipfit-dogma-engine[sde]

import esf_dogma_engine as dogma
from eveshipfit_sde import sde_path

build_number = dogma.load_sde_from_file(sde_path())

fit = {
    "ship": {"type_id": 587},
    "items": [
        {
            "type_id": 2873,
            "slot": {"type": "high", "index": 0},
            "state": "active",
            "charge": {"type_id": 185},
        }
    ],
    "character": {"skills": {3300: 5}},
}

calculation = dogma.calculate(fit)
# Or if you want to know the source of the effects:
with_sources = dogma.calculate(fit, {"sources": True})
# Or if you have a beacon in space (like wormhole effects):
with_beacon = dogma.calculate({**fit, "incoming": dogma.beacon(beacon_type_id)})
# Or if you have an EFT, the text format EVE copies a fit to the clipboard in:
imported = dogma.calculate(dogma.load_eft("[Rifter, My Rifter]\n200mm AutoCannon I"))
# And to write a fit back out as EFT:
eft = dogma.save_eft(fit)

# What EVE would not let you fly; it calculates the fit itself:
violations = dogma.validate(fit)

Fits and calculations are plain dicts, typed with TypedDict in esf_dogma_engine.types.

load_eft, calculate and beacon release the GIL while they work, so a thread pool calculates fits in parallel.

Development

Make sure you have Rust installed.

Next, we need the data-files. They are Flatbuffers, built by sde-patched and published on npm as @eveshipfit/sde:

npm ci

• sde.dat holds everything needed to calculate a fit.
• names.dat holds the type names in the other seven languages EVE supports. It is optional.

English names live in sde.dat, so an EFT-fit written in English imports without it; names.dat is only consulted when a name does not match.

After that, we can run the application.

flatc --rust --gen-onefile -o crates/esf-data/src/sde/ node_modules/@eveshipfit/sde/specs/eve.fbs node_modules/@eveshipfit/sde/specs/names.fbs
cargo run --release -p esf-cli

For example, some attributes of a fit with every skill at L0 except two:

printf '[Nergal, Spool]\nLight Entropic Disintegrator II, Occult S\n' \
  | cargo run --release -p esf-cli -- -l 0 --skill "Gunnery=4" --skill "Rapid Firing=2" -a damage -a speed

It prints a table on a terminal and JSON otherwise; see --help for the rest.

Or to write the fit back out as EFT, instead of calculating it:

printf '[Nergal, Spool]\nLight Entropic Disintegrator II, Occult S\n' \
  | cargo run --release -p esf-cli -- --eft

The regression suite reads the same paths; set ESF_SDE and ESF_NAMES to point it elsewhere.

Regression

The engine is locked down by snapshot tests. A case calculates one fit with one set of skills, and compares the result against a stored snapshot in tests/snapshots.

cargo test

If failures are expected differences, use insta to resolve them:

cargo install cargo-insta
cargo insta review

Integration

Every variant is built from the same Rust crates; the flatc step from Development comes first.

Rust

The engine itself is a plain crate; esf-cli is an example of using it.

cargo build --release -p esf-dogma-engine

Javascript (WebAssembly)

The primary goal of this library is to build a WebAssembly variant that can easily be used in the browser. This means that there is no need for a server-component, and everything can be calculated in the browser.

This is done with wasm-pack:

cargo install wasm-pack
wasm-pack build crates/esf-wasm --release --out-dir ../../pkg

In the pkg folder is now a NPM module to use.

Python

This is done with maturin:

cargo install maturin
maturin build --release

In the target/wheels folder is now a wheel to install.