mp-ir

Mixed-precision iterative refinement. mp-ir composes two header-only libraries — MTL5 for linear algebra and Universal for parameterized number systems — to study iterative refinement: factor a system in a low working precision, then recover accuracy by correcting the solution with a higher-precision residual (half precision, posits, ... as the working type).

MTL5 deliberately has no dependency on Universal: it is the general linear-algebra layer, and it already ships a Universal-free sparse iterative_refine core. mp-ir is the integration layer where MTL5's dense LU and Universal's number types meet — the mixed-precision experiments live here.

# Dependencies (MTL5 + Universal) are pulled automatically via FetchContent.
cmake -B build -DCMAKE_BUILD_TYPE=Release
cmake --build build -j

# Run the smoke test
ctest --test-dir build --output-on-failure

# Run the precision study (optional arg: problem size)
./build/applications/dense_lu/lu_ir_precision/lu_ir_precision 8

# Run the benchmark (optional arg: problem size)
./build/benchmarks/dense_lu/lu_ir_benchmark 64

Using local checkouts instead of fetching from GitHub:

cmake -B build \
  -DFETCHCONTENT_SOURCE_DIR_MTL5=../mtl5 \
  -DFETCHCONTENT_SOURCE_DIR_UNIVERSAL=../universal

The repo is organized by iterative-refinement category: dense_lu (LU factor

• refine), scaling (round-and-replace / scale-and-round squeeze strategies), and sparse (sparse direct factor + refine, driving MTL5's core).

include/sw/mp_ir/
  lu_iterative_refinement.hpp    # re-exports MTL5 core (mtl::lu_iterative_refine)
include/mtl/math/
  quire_accumulator.hpp          # MTL5 accumulator_traits <- Universal quire bridge
applications/
  dense_lu/lu_ir_precision/      # refined-vs-unrefined residual across precisions
benchmarks/
  dense_lu/                      # factor/refine timing + steps-to-floor
tests/
  dense_lu/                      # LU-IR smoke test + migrated luir experiment
  scaling/                       # squeeze preconditioners (round/scale/two-sided)
  sparse/                        # (no tests yet -- see docs/roadmap.md)
docs/roadmap.md                  # milestones and migration plan

MIT — see LICENSE.