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RemapIndices.cpp
/**
* Copyright (c) 2015-present, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the CC-by-NC license found in the
* LICENSE file in the root directory of this source tree.
*/
// Copyright 2004-present Facebook. All Rights Reserved.
#include "RemapIndices.h"
#include "../../FaissAssert.h"
namespace faiss { namespace gpu {
// Utility function to translate (list id, offset) to a user index on
// the CPU. In a cpp in order to use OpenMP
void ivfOffsetToUserIndex(
long* indices,
int numLists,
int queries,
int k,
const std::vector<std::vector<long>>& listOffsetToUserIndex) {
FAISS_ASSERT(numLists == listOffsetToUserIndex.size());
#pragma omp parallel for
for (int q = 0; q < queries; ++q) {
for (int r = 0; r < k; ++r) {
long offsetIndex = indices[q * k + r];
if (offsetIndex < 0) continue;
int listId = (int) (offsetIndex >> 32);
int listOffset = (int) (offsetIndex & 0xffffffff);
FAISS_ASSERT(listId < numLists);
auto& listIndices = listOffsetToUserIndex[listId];
FAISS_ASSERT(listOffset < listIndices.size());
indices[q * k + r] = listIndices[listOffset];
}
}
}
} } // namespace