From 3658abe455ac824f0c09a592c5452659e1174bd8 Mon Sep 17 00:00:00 2001
From: Hao Zhang <hzhangxyz@outlook.com>
Date: Sun, 19 Nov 2023 04:45:29 +0800
Subject: [PATCH] Fix imaginary part discarding warning in `to` function.

---
 tat/tensor.py | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/tat/tensor.py b/tat/tensor.py
index eec49f92f..72691ec26 100644
--- a/tat/tensor.py
+++ b/tat/tensor.py
@@ -422,12 +422,16 @@ def to(self: Tensor, new_type: typing.Any) -> Tensor:
                 new_type = torch.complex64
             elif new_type in ["complex128", "complex", "Z"]:
                 new_type = torch.complex128
+        if self.dtype.is_complex and new_type.is_floating_point:
+            data = self.data.real.to(new_type)
+        else:
+            data = self.data.to(new_type)
         return Tensor(
             names=self.names,
             edges=self.edges,
             fermion=self.fermion,
             dtypes=self.dtypes,
-            data=self.data.to(new_type),
+            data=data,
             mask=self.mask,
         )