Ultimate Performance Mod: Reductio – 22% smaller map (Faster map)

Part of the Ultimate Mod Collection. A reduction-based performance submod for UPM (Ultimate Performance Mod).

Reductio ships a permanently smaller world map. It merges adjacent, historically-minor locations into their neighbours — cutting the location count, and with it the buildings, market participants, map meshes and GUI sweeps that every location carries. Less of the map to simulate, every year, from 1337 to 1837.

EU5 ships ~28,573 locations. Reductio merges the over-granular ones down to ~22,194 — a 22.3% map-wide reduction — while keeping the parts of the map you actually recognise and interact with.

• Fewer pops — pops live inside locations; fewer locations means fewer pops to tick.
• Fewer buildings & market participants — cut at the source.
• Lighter map render & GUI — fewer meshes, markers and per-location sweeps.
• Uniform — the win applies in the early game too, not just the late game.

Reductio never touches province, area or region borders — only the tiles inside a province are consolidated. A set of conservative, automated rules guarantees the map stays coherent and historical.

• Floor of 3 — every province keeps at least three populated locations.
• Max 50% — no province loses more than half its locations.
• Same culture + religion + adjacency — merges never blur cultural or religious borders, and the merged tile is always contiguous.
• Protected locations always survive — capitals, holy sites, trade-market centres and any location referenced by an event, decision or mission are never merged away.

Same provinces, same shape of the world — just fewer tiles to manage and simulate.

The densest, most over-granular regions give up the most tiles; sparse and historically-detailed areas are left largely intact.

Reductio is a base map mod. That has consequences:

• Hard-incompatible with other map mods and with content mods that reference specific locations by ID.
• Saves are map-bound — a game started on the Reductio map cannot be continued on vanilla, and vice-versa. This is not a toggle.
• Designed to sit under the UPM performance stack and the rest of the Ultimate Mod Collection.

Always start a new game after enabling or disabling this mod.

• UPM — Ultimate Performance Mod (AI cadence, event gating, culling)
• Reductio — this mod (structural map reduction)
• UGM — Ultimate Gameplay Mod
• UVM — Ultimate Visual Mod
• UCT — Ultimate Cheat Tool

The merged map is produced by a deterministic, fully-scripted toolchain: a candidate selector applies the rules above, a merge driver rewrites the entire map-data and setup cascade (locations image, definitions, pops, ownership, roads, ports, localization in 11 languages…), and a validator proves no merged location is left referenced anywhere — guaranteeing a clean, crash-free map. The spline-network and map-object locators are re-baked in the official map editor against the reduced map.

Built for EU5 1.2.x.