Feat/pecos num (#201)

* Add Rust general numerical methods

Author: ciaranra

Cargo.lock

@@ -85,6 +85,12 @@ tket = "0.16"
 tket-qsystem = { version = "0.22", default-features = false }
 ndarray = "0.16"
 anyhow = "1"
+
+# Numerical computing dependencies (for pecos-num)
+peroxide = "0.40"
+roots = "0.0.8"
+levenberg-marquardt = "0.15"
+nalgebra = "0.34"
 cxx = "1.0.187"
 cxx-build = "1.0.187"
 reqwest = { version = "0.12", default-features = false, features = ["blocking", "rustls-tls"] }
@@ -126,6 +132,7 @@ pecos-rslib = { version = "0.1.1", path = "python/pecos-rslib/rust" }
 pecos-wasm = { version = "0.1.1", path = "crates/pecos-wasm" }
 pecos-build-utils = { version = "0.1.1", path = "crates/pecos-build-utils" }
 pecos-llvm-utils = { version = "0.1.1", path = "crates/pecos-llvm-utils" }
+pecos-num = { version = "0.1.1", path = "crates/pecos-num" }
 
 # Decoder crates
 pecos-decoder-core = { version = "0.1.1", path = "crates/pecos-decoder-core" }

Cargo.toml

@@ -327,7 +327,7 @@ decoder-cache-clean: ## Clean decoder download cache
 .PHONY: pytest
 pytest:  ## Run tests on the Python package (not including optional dependencies). ASSUMES: previous build command
 	@$(ADD_LLVM_TO_PATH) uv run pytest ./python/quantum-pecos/tests/ --doctest-modules -m "not optional_dependency"
-	@$(ADD_LLVM_TO_PATH) uv run pytest ./python/pecos-rslib/tests/
+	@$(ADD_LLVM_TO_PATH) uv run --with scipy --with numpy pytest ./python/pecos-rslib/tests/
 	@$(ADD_LLVM_TO_PATH) uv run pytest ./python/slr-tests/ -m "not optional_dependency"
 
 .PHONY: pytest-dep
@@ -337,7 +337,7 @@ pytest-dep: ## Run tests on the Python package only for optional dependencies. A
 .PHONY: pytest-all
 pytest-all: ## Run all tests on the Python package ASSUMES: previous build command
 	@$(ADD_LLVM_TO_PATH) uv run pytest ./python/quantum-pecos/tests/ -m ""
-	@$(ADD_LLVM_TO_PATH) uv run pytest ./python/pecos-rslib/tests/
+	@$(ADD_LLVM_TO_PATH) uv run --with scipy --with numpy pytest ./python/pecos-rslib/tests/
 
 # .PHONY: pytest-doc
 # pydoctest:  ## Run doctests with pytest. ASSUMES: A build command was ran previously. ASSUMES: previous build command

Makefile

@@ -0,0 +1,32 @@
+[package]
+name = "pecos-num"
+version.workspace = true
+edition.workspace = true
+authors.workspace = true
+homepage.workspace = true
+repository.workspace = true
+license.workspace = true
+keywords.workspace = true
+categories.workspace = true
+readme.workspace = true
+description = "Numerical computing support for PECOS quantum error correction simulations"
+
+[dependencies]
+# Comprehensive numerical computing library (for Newton, polynomial fitting)
+peroxide.workspace = true
+
+# Root finding (for Brent's method only - Peroxide doesn't have it)
+roots.workspace = true
+
+# Curve fitting (scipy-compatible API, better match than Peroxide's AD-based optimizer)
+levenberg-marquardt.workspace = true
+nalgebra.workspace = true  # Required by levenberg-marquardt
+
+# Array interface (for API compatibility and return types)
+ndarray.workspace = true
+
+# Logging
+log.workspace = true
+
+[lints]
+workspace = true

crates/pecos-num/Cargo.toml

@@ -0,0 +1,36 @@
+# pecos-num
+
+`pecos-num` provides numerical computing support for PECOS quantum error correction simulations.
+
+This crate brings together numerical computing dependencies and implements functionality needed for QEC analysis in PECOS, including threshold fitting, data analysis, and optimization. It provides APIs with similar functionality to scipy and numpy for numerical operations.
+
+## Features
+
+- Root finding algorithms (Brent's method, Newton-Raphson)
+- Non-linear curve fitting (Levenberg-Marquardt)
+- Polynomial fitting and evaluation
+- Built on robust Rust numerical libraries (Peroxide, levenberg-marquardt, nalgebra)
+
+## Usage
+
+This is an **internal crate** used by:
+- `pecos` - The main PECOS metacrate (via prelude)
+- `pecos-rslib` - Python bindings exposing numerical functions
+
+For direct usage in Rust:
+
+```rust
+use pecos_num::prelude::*;
+
+// Root finding with Brent's method
+let root = brentq(|x| x * x - 2.0, 0.0, 2.0, None).unwrap();
+
+// Curve fitting
+let result = curve_fit(
+    |x, params| params[0] * x + params[1],
+    xdata.view(),
+    ydata.view(),
+    p0.view(),
+    None
+).unwrap();
+```