Add block-spin update sampler

dwave/plugins/torch/nn/functional.py

@@ -0,0 +1,56 @@
+# Copyright 2025 D-Wave
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+"""Functional interface."""
+
+import torch
+
+__all__ = ["bit2spin_soft", "spin2bit_soft"]
+
+
+def bit2spin_soft(b: torch.Tensor) -> torch.Tensor:
+    """Maps input :math:`b` to :math:`2b-1`.
+
+    The mapping does not require :math:`b` to be binary, only that it is in the interval :math:`[0, 1]`.
+
+    Args:
+        b (torch.Tensor): Input tensor of values in :math:`[0, 1]`.
+
+    Raises:
+        ValueError: If not all ``b`` values are in :math:`[0, 1]`.
+
+    Returns:
+        torch.Tensor: A tensor with values :math:`2b-1`.
+    """
+    if not ((b >= 0) & (b <= 1)).all():
+        raise ValueError(f"Not all inputs are in [0, 1]: {b}")
+    return b * 2 - 1
+
+
+def spin2bit_soft(s: torch.Tensor) -> torch.Tensor:
+    """Maps input :math:`s` to :math:`(s+1)/2`.
+
+    The mapping does not require :math:`s` to be spin-valued, only that it is in the interval :math:`[-1, 1]`.
+
+    Args:
+        s (torch.Tensor): Input tensor of values in :math:`[-1, 1]`.
+
+    Raises:
+        ValueError: If not all ``s`` values are in `[-1, 1]`.
+
+    Returns:
+        torch.Tensor: A tensor with values :math:`(s+1)/2`.
+    """
+    if (s.abs() > 1).any():
+        raise ValueError(f"Not all inputs are in [-1, 1]: {s}")
+    return (s + 1) / 2

dwave/plugins/torch/samplers/__init__.py

@@ -0,0 +1,15 @@
+# Copyright 2025 D-Wave
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+from dwave.plugins.torch.samplers.block_spin_sampler import *