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/*
* Copyright (c) Meta Platforms, Inc. and affiliates.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*/
#include <gtest/gtest.h>
#include <chrono>
#include <cstdint>
#include <random>
#include <sstream>
#include <string>
#include <unordered_set>
#include <vector>
#include <faiss/utils/approx_topk/approx_topk.h>
#include <faiss/impl/FaissException.h>
#include <faiss/utils/Heap.h>
//
using namespace faiss;
//
template <uint32_t NBUCKETS, uint32_t N>
void test_approx_topk(
const uint32_t beamSize,
const uint32_t nPerBeam,
const uint32_t k,
const uint32_t nDatasetsToTest,
const bool verbose) {
if (verbose) {
printf("-----------\n");
}
// generate random data
std::default_random_engine rng(123);
std::uniform_real_distribution<float> u(0, 1);
// matches
size_t nMatches = 0;
// the element was completely missed in approx version.
size_t nMissed = 0;
// the element is available
size_t nAvailable = 0;
// the distance is the same, but the index is different.
size_t nSoftMismatches = 0;
// the distances are different
size_t nHardMismatches = 0;
// error of distances
double sqrError = 0.0;
//
double timeBaseline = 0.0;
double timeApprox = 0.0;
for (size_t iDataset = 0; iDataset < nDatasetsToTest; iDataset++) {
const size_t n = (size_t)(nPerBeam)*beamSize;
std::vector<float> distances(n, 0);
for (size_t i = 0; i < n; i++) {
distances[i] = u(rng);
}
//
using C = CMax<float, int>;
// do a regular beam search
std::vector<float> baselineDistances(k, C::neutral());
std::vector<int> baselineIndices(k, -1);
auto startBaseline = std::chrono::high_resolution_clock::now();
heap_addn<C>(
k,
baselineDistances.data(),
baselineIndices.data(),
distances.data(),
nullptr,
nPerBeam * beamSize);
auto endBaseline = std::chrono::high_resolution_clock::now();
std::chrono::duration<double> diffBaseline =
endBaseline - startBaseline;
timeBaseline += diffBaseline.count();
heap_reorder<C>(k, baselineDistances.data(), baselineIndices.data());
// do an approximate beam search
std::vector<float> approxDistances(k, C::neutral());
std::vector<int> approxIndices(k, -1);
auto startApprox = std::chrono::high_resolution_clock::now();
try {
HeapWithBuckets<C, NBUCKETS, N>::bs_addn(
beamSize,
nPerBeam,
distances.data(),
k,
approxDistances.data(),
approxIndices.data());
} catch (const faiss::FaissException&) {
//
if (verbose) {
printf("Skipping the case.\n");
}
return;
}
auto endApprox = std::chrono::high_resolution_clock::now();
std::chrono::duration<double> diffApprox = endApprox - startApprox;
timeApprox += diffApprox.count();
heap_reorder<C>(k, approxDistances.data(), approxIndices.data());
bool bGotMismatches = false;
// the error
for (uint32_t i = 0; i < k; i++) {
if (baselineDistances[i] != approxDistances[i]) {
nHardMismatches += 1;
double diff = baselineDistances[i] - approxDistances[i];
sqrError += diff * diff;
bGotMismatches = true;
if (verbose) {
printf("i=%d, bs.d=%f, bs.i=%d, app.d=%f, app.i=%d\n",
i,
baselineDistances[i],
baselineIndices[i],
approxDistances[i],
approxIndices[i]);
}
} else {
if (baselineIndices[i] != approxIndices[i]) {
nSoftMismatches += 1;
} else {
nMatches += 1;
}
}
}
if (bGotMismatches) {
if (verbose) {
printf("\n");
}
}
//
std::unordered_set<int> bsIndicesHS(
baselineIndices.cbegin(), baselineIndices.cend());
for (uint32_t i = 0; i < k; i++) {
auto itr = bsIndicesHS.find(approxIndices[i]);
if (itr != bsIndicesHS.cend()) {
nAvailable += 1;
} else {
nMissed += 1;
}
}
}
if (verbose) {
printf("%d, %d, %d, %d, %d, %d: %zu, %zu, %zu, %f, %zu, %zu, %f, %f\n",
NBUCKETS,
N,
beamSize,
nPerBeam,
k,
nDatasetsToTest,
nMatches,
nSoftMismatches,
nHardMismatches,
sqrError,
nAvailable,
nMissed,
timeBaseline,
timeApprox);
}
// just confirm that the error is not crazy
if (NBUCKETS * N * beamSize >= k) {
EXPECT_TRUE(nAvailable > nMissed);
} else {
// it is possible that the results are crazy here. Skip it.
}
}
//
TEST(testApproxTopk, COMMON) {
constexpr bool verbose = false;
//
const uint32_t nDifferentDatasets = 8;
uint32_t kValues[] = {1, 2, 3, 5, 8, 13, 21, 34};
for (size_t codebookBitSize = 8; codebookBitSize <= 10; codebookBitSize++) {
const uint32_t codebookSize = 1 << codebookBitSize;
for (const auto k : kValues) {
test_approx_topk<1 * 8, 3>(
1, codebookSize, k, nDifferentDatasets, verbose);
test_approx_topk<1 * 8, 3>(
k, codebookSize, k, nDifferentDatasets, verbose);
test_approx_topk<1 * 8, 2>(
1, codebookSize, k, nDifferentDatasets, verbose);
test_approx_topk<1 * 8, 2>(
k, codebookSize, k, nDifferentDatasets, verbose);
test_approx_topk<2 * 8, 2>(
1, codebookSize, k, nDifferentDatasets, verbose);
test_approx_topk<2 * 8, 2>(
k, codebookSize, k, nDifferentDatasets, verbose);
test_approx_topk<4 * 8, 2>(
1, codebookSize, k, nDifferentDatasets, verbose);
test_approx_topk<4 * 8, 2>(
k, codebookSize, k, nDifferentDatasets, verbose);
}
}
}
//
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