hotfix(HatBasisQFE): fix negative sqrt

CHANGELOG.md

@@ -5,6 +5,12 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [0.6.2] - 2024-02-06
+
+### Fixed
+
+- Hat basis negative close to 0 values, sqrt in HatBasisQFE returned nan
+
 ## [0.6.1] - 2024-02-05
 
 ### Fixed

pyproject.toml

@@ -1,6 +1,6 @@
 [tool.poetry]
 name = "qulearn"
-version = "0.6.1"
+version = "0.6.2"
 description = "Streamlining quantum and classical machine learning model development."
 authors = ["Mazen Ali <[email protected]>"]
 readme = "README.md"

qulearn/qlayer.py

@@ -156,8 +156,9 @@ def circuit(self, x: Tensor) -> None:
         a, b = self.basis.nonz_vals(x)
 
         if self.sqrt:
-            a = torch.sqrt(a)
-            b = torch.sqrt(b)
+            # sometimes the values are close to 0 and negative
+            a = torch.sqrt(torch.abs(a))
+            b = torch.sqrt(torch.abs(b))
 
         if position == -1:
             self.norm = b.item()