add broadcasting functions

include/aidge/backend/cpu/data/Broadcasting.hpp

+/********************************************************************************
+ * Copyright (c) 2024 CEA-List
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ ********************************************************************************/
+
+#ifndef AIDGE_CPU_DATA_BROADCASTING_H_
+#define AIDGE_CPU_DATA_BROADCASTING_H_
+
+#include <vector>
+
+namespace Aidge {
+
+// Function to broadCast an input dims vector into the same size as an outputDims vector
+std::vector<std::size_t> getBroadcastedDims(const std::vector<std::size_t>& outputDims, const std::vector<std::size_t>& dimsToBroadcast);
+
+// Function to get multi-dimensional indices from a flattened index
+std::vector<std::size_t> getMultiDimIndices(const std::vector<std::size_t>& dimensions, std::size_t idx);
+
+// Function to get a flattened index from multi-dimensional indices
+std::size_t getFlattenedIndex(const std::vector<std::size_t>& dimensions, const std::vector<std::size_t>& indices);
+
+} // namespace Aidge
+
+#endif // AIDGE_CPU_DATA_BROADCASTING_H_
\ No newline at end of file

src/data/Broadcasting.cpp

+/********************************************************************************
+ * Copyright (c) 2024 CEA-List
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0.
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ *
+ ********************************************************************************/
+
+#include "aidge/backend/cpu/data/Broadcasting.hpp"
+
+std::vector<std::size_t> Aidge::getBroadcastedDims(const std::vector<std::size_t>& outputDims, const std::vector<std::size_t>& dimsToBroadcast){
+    std::vector<std::size_t> broadcastedDims(outputDims.size(), 1);
+		for(std::size_t j=dimsToBroadcast.size()-1; j+1>0; --j)
+		{
+			std::size_t idx = outputDims.size() - (dimsToBroadcast.size()-j);
+			broadcastedDims[idx] = dimsToBroadcast[j];
+		}
+    return broadcastedDims;
+}
+
+std::vector<std::size_t> Aidge::getMultiDimIndices(const std::vector<size_t>& dimensions, std::size_t idx){
+    std::vector<std::size_t> indices(dimensions.size(), 0);
+
+    for (int i = dimensions.size() - 1; i >= 0; --i) {
+        indices[i] = idx % dimensions[i];
+        idx /= dimensions[i];
+    }
+
+    return indices;
+}
+
+std::size_t Aidge::getFlattenedIndex(const std::vector<std::size_t>& dimensions, const std::vector<std::size_t>& indices){
+    std::size_t flattenedIdx = 0;
+    std::size_t stride = 1;
+
+    for (int i = dimensions.size() - 1; i >= 0; --i) {
+        std::size_t idx = dimensions[i]>1 ? indices[i] : 0;
+        flattenedIdx += idx * stride;
+        stride *= dimensions[i];
+    }
+    return flattenedIdx;
+}
+