Presented at Activate 2018

1. Speeding up Lucene using
GPUs
Ishan Chattopadhyaya
Committer & PMC Member, Apache Lucene/Solr
Kishore Angani
Senior Search Architect, Unbxd
@ichattopadhyaya @kishore_angani
#Activate18 #ActivateSearch

2. Agenda
• Brief History of Computers
• GPGPU computing
• Inverted Index
• Searching on GPU
 Spatial Search
 BM25
 Advanced Scoring
 Faceting
• Work ahead

3. Brief History of Computers

4. What is GPGPU computing?

5. What is an Inverted Index?

6. Search on GPU
 Spatial Search
 Native scoring (BM25)
 Faceting
 Advanced Scoring

7. LUCENE-7745

8. Spatial Search

9. Spatial Search: Code
int *docs;
float *lats, *lngs;
long N;
device_vector<int> gpu_docs;
device_vector<float> gpu_lats, gpu_lngs;
JNIEXPORT jint JNICALL Java_GpuGeoDist_initIndex(JNIEnv *env, jobject obj, jintArray docIdsArray,
jfloatArray latsArray, jfloatArray lngsArray) {
N = env->GetArrayLength(docIdsArray);
docs = env->GetIntArrayElements(docIdsArray, NULL);
lats = env->GetFloatArrayElements(latsArray, NULL);
lngs = env->GetFloatArrayElements(lngsArray, NULL);
// Copy the vectors to the device
host_vector<int> cpu_docs(N);
for (int i=0; i<N; i++) cpu_docs[i] = docs[i];
gpu_docs = cpu_docs;
host_vector<float> cpu_lats(N);
for (int i=0; i<N; i++) cpu_lats[i] = lats[i];
gpu_lats = cpu_lats;
host_vector<float> cpu_lngs(N);
for (int i=0; i<N; i++) cpu_lngs[i] = lngs[i];
gpu_lngs = cpu_lngs;
}

10. Spatial Search: Code
JNIEXPORT jobject JNICALL Java_GpuGeoDist_findNearest(JNIEnv *env, jobject obj, jfloat lat, jfloat lng)
{
// Actual scoring/sorting on device
device_vector<float> gpu_distances(N);
transform(gpu_lats.begin(), gpu_lats.end(), gpu_lngs.begin(), gpu_distances.begin(), geodist(lat, lng));
device_vector<int> docIds = gpu_docs;
thrust::sort_by_key(gpu_distances.begin(), gpu_distances.end(), docIds.begin());
int *docs = (int*)malloc(N*4*2);
float *distances = &((float*)docs)[N];
thrust::copy(docIds.begin(), docIds.end(), docs);
thrust::copy(gpu_distances.begin(), gpu_distances.end(), distances);
jobject directBuffer = env->NewDirectByteBuffer((void*)docs, N*2*4);
return directBuffer;
}
struct geodist {
const float refX,refY;
geodist(float _x, float _y): refX(_x), refY(_y) {}
__host__ __device__ float operator()(float &x, float &y) const {
return sqrt((x - refX) * (x-refX) + (y-refY)*(y-refY));
}
};

11. Spatial Search: Benchmarks

12. Native Scoring (BM25): Formula

13. Native Scoring (BM25): Initialization
 Postings
 Norms
 Inverted Document Frequencies

14. Native Scoring (BM25): Query
processing
 Term dictionary lookup
 Scattering term rows
 Computing term scores
 Sorting by scores

15. Native Scoring (BM25): Code

16. Native Scoring (BM25): Benchmarks

17. Advanced Scoring

18. Faceting

19. Work ahead

20. Thank you!
Ishan Chattopadhyaya
Committer & PMC Member, Apache Lucene/Solr
Kishore Angani
Senior Search Architect, Unbxd
@ichattopadhyaya @kishore_angani
#Activate18 #ActivateSearch

21. Thank you!
Ishan Chattopadhyaya
Committer & PMC Member, Apache Lucene/Solr
Kishore Angani
Senior Search Architect, Unbxd
@ichattopadhyaya @kishore_angani
#Activate18 #ActivateSearch