Usage Example

This section provides a simple example to describe how to use Index SDK for retrieval.

The following example demonstrates how to call an index API using the Flat algorithm to retrieve 128 vectors from a 1M-sized 512-dimensional database with topK being 10.

Prerequisite

Operations described in Installation and Deployment have been completed.
The Flat and AICPU operators have been generated.

Procedure

Construct a demo as follows.

Import the Flat header file.
Construct vector data. Random numbers are used in this example.
Normalize vectors.
Initializes the Flat index.
Call an API to add vectors to the index.
Call an API for retrieval.

The demo.cpp code is as follows:

#include <faiss/ascend/AscendIndexFlat.h>
#include <sys/time.h>
#include <random>
// Obtain the current time.
inline double GetMillisecs()
{
    struct timeval tv = {0, 0};
    gettimeofday(&tv, nullptr);
    return tv.tv_sec * 1e3 + tv.tv_usec * 1e-3;
}
// Use random numbers to construct vector data.
void Generate(size_t ntotal, std::vector<float> &data, int seed = 5678)
{
    std::default_random_engine e(seed);
    std::uniform_real_distribution<float> rCode(0.0f, 1.0f);
    data.resize(ntotal);
    for (size_t i = 0; i < ntotal; ++i) {
        data[i] = static_cast<float>(255 * rCode(e) - 128);
    }
}
// Normalize vectors.
void Norm(size_t total, std::vector<float> &data, int dim)
{
    for (size_t i = 0; i < total; ++i) {
        float mod = 0;
        for (int j = 0; j < dim; ++j) {
            mod += data[i * dim + j] * data[i * dim + j];
        }
        mod = sqrt(mod);
        for (int j = 0; j < dim; ++j) {
            data[i * dim + j] = data[i * dim + j] / mod;
        }
    }
}
int main()
{
    int dim = 512;
    std::vector<int> device{0};
    size_t ntotal = 1000000;
    int searchnum = 128;
    std::vector<float> features(dim * ntotal);
    int64_t resourceSize = static_cast<int64_t>(1024) * 1024 * 1024;
    int topK = 10;
    printf("Generating random numbers start!\r\n");
    Generate(ntotal, features);
    Norm(ntotal, features, dim);
    try {
       // Initialize the index.
        faiss::ascend::AscendIndexFlatConfig conf(device, resourceSize);
        auto metricType = faiss::METRIC_INNER_PRODUCT;
        faiss::ascend::AscendIndexFlat index(dim, metricType, conf);
        index.reset();
       // Add vectors to the index.
        printf("add start!\r\n");
        index.add(ntotal, features.data());
        size_t tmpTotal = index.getBaseSize(0);
        if (tmpTotal != ntotal) {
            printf("------- Error -----------------\n");
            return -1;
        }
        // search
        printf("search start!\r\n");
        int loopTimes = 1;
        std::vector<float> dist(searchnum * topK, 0);
        std::vector<faiss::idx_t> label(searchnum * topK, 0);
        auto ts = GetMillisecs();
        for (int i = 0; i < loopTimes; i++) {
            index.search(searchnum, features.data(), topK, dist.data(), label.data());
        }
        auto te = GetMillisecs();
        printf("search end!\r\n");
        printf("flat, base:%lu, dim:%d, searchnum:%d, topk:%d, duration:%.3lf, QPS:%.4f\n",
            ntotal,
            dim,
            searchnum,
            topK,
            te - ts,
            1000 * searchnum * loopTimes / (te - ts));
        return 0;
    } catch(...) {
        printf("Exception caught! \r\n");
        return -1;
    }
}

Compile demo.cpp.

# The installation path /home/work/FeatureRetrieval is used as an example.
g++ --std=c++11 -fPIC -fPIE -fstack-protector-all -Wall -D_FORTIFY_SOURCE=2 -O3  -Wl,-z,relro,-z,now,-z,noexecstack -s -pie \
-o demo demo.cpp \
-I/home/work/FeatureRetrieval/mxIndex/include \
-I/usr/local/faiss/faiss1.10.0/include \
-I/usr/local/Ascend/driver/include \
-I/opt/OpenBLAS/include \
-L/home/work/FeatureRetrieval/mxIndex/host/lib \
-L/usr/local/faiss/faiss1.10.0/lib \
-L/usr/local/Ascend/driver/lib64 \
-L/usr/local/Ascend/driver/lib64/driver \
-L/opt/OpenBLAS/lib \
-L/usr/local/Ascend/ascend-toolkit/latest/lib64 \
-lfaiss -lascendfaiss -lopenblas -lc_sec -lascendcl -lascend_hal -lascendsearch -lock_hmm -lacl_op_compiler

Run the demo. If "search end!" is displayed, the demo is successfully executed.
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./demo ... search end!