Knot Floer Homology

1.2.2 verified Fri May 01 auth: no python

Python wrapper for Zoltán Szabó's HFK (Heegaard Floer Knot homology) Calculator. Computes knot Floer homology invariants including the tau invariant, epsilon invariant, and the full HFK chain complex. Current version 1.2.2, with periodic releases.

pip install knot-floer-homology

Common errors

error knot_floer_homology has no attribute 'compute' ↓

cause Incorrect import or outdated version (older API).

fix

Update to >=1.0.0 and use kfh.compute(manifold, prime=...).

error OverflowError: integer overflow for prime >= 1297 ↓

cause Bug in version <1.1 when using large primes.

fix

Upgrade to v1.1 or later.

error ModuleNotFoundError: No module named 'knot_floer_homology' ↓

cause Trying to import with hyphens or not installed.

fix

Install with pip install knot-floer-homology, then import knot_floer_homology (underscores).

Warnings

breaking The fast algorithm for alternating knots was removed in v1.2 due to bug #17. All knots now use the same algorithm, which may be slower for large alternating knots. ↓

fix No fix needed; just aware that performance may differ from earlier versions.

deprecated Dependency on sphereogram package was removed in v1.2.1. If you relied on sphereogram for other purposes, you need to install it separately. ↓

fix Install sphereogram independently if needed: pip install sphereogram

gotcha Interrupting long computations with Control-C was only added in v1.1. In older versions, interrupting could leave the C++ backend in an inconsistent state. ↓

fix Upgrade to v1.1 or later.

gotcha The module name uses underscores (knot_floer_homology) but the PyPI package name uses hyphens (knot-floer-homology). Import with underscores. ↓

fix Use import knot_floer_homology

Imports

knot_floer_homology
```
import knot_floer_homology
```
Standard import; no common wrong pattern.

Quickstart

Basic usage: compute knot Floer homology for the trefoil knot over Z/2Z using snappy's Manifold.

import knot_floer_homology as kfh
import snappy

# Create a knot (trefoil)
K = snappy.Manifold('3_1')

# Compute knot Floer homology (mod 2)
result = kfh.compute(K, prime=2)
print("Tau:", result.tau)
print("Epsilon:", result.epsilon)
print("Rank of HFK:", result.hfk_rank)