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/tmp/faiss/utils.cpp
/**
* Copyright (c) 2015-present, Facebook, Inc.
* All rights reserved.
*
* This source code is licensed under the BSD+Patents license found in the
* LICENSE file in the root directory of this source tree.
*/
// -*- c++ -*-
#include "utils.h"
#include <cstdio>
#include <cassert>
#include <cstring>
#include <cmath>
#include <sys/time.h>
#include <sys/types.h>
#include <unistd.h>
#include <omp.h>
#include <immintrin.h>
#include <algorithm>
#include <vector>
#include "AuxIndexStructures.h"
#include "FaissAssert.h"
#ifndef FINTEGER
#define FINTEGER long
#endif
extern "C" {
/* declare BLAS functions, see http://www.netlib.org/clapack/cblas/ */
int sgemm_ (const char *transa, const char *transb, FINTEGER *m, FINTEGER *
n, FINTEGER *k, const float *alpha, const float *a,
FINTEGER *lda, const float *b, FINTEGER *
ldb, float *beta, float *c, FINTEGER *ldc);
/* Lapack functions, see http://www.netlib.org/clapack/old/single/sgeqrf.c */
int sgeqrf_ (FINTEGER *m, FINTEGER *n, float *a, FINTEGER *lda,
float *tau, float *work, FINTEGER *lwork, FINTEGER *info);
int sorgqr_(FINTEGER *m, FINTEGER *n, FINTEGER *k, float *a,
FINTEGER *lda, float *tau, float *work,
FINTEGER *lwork, FINTEGER *info);
int sgemv_(const char *trans, FINTEGER *m, FINTEGER *n, float *alpha,
const float *a, FINTEGER *lda, const float *x, FINTEGER *incx,
float *beta, float *y, FINTEGER *incy);
}
/**************************************************
* Get some stats about the system
**************************************************/
namespace faiss {
double getmillisecs () {
struct timeval tv;
gettimeofday (&tv, nullptr);
return tv.tv_sec * 1e3 + tv.tv_usec * 1e-3;
}
#ifdef __linux__
size_t get_mem_usage_kb ()
{
int pid = getpid ();
char fname[256];
snprintf (fname, 256, "/proc/%d/status", pid);
FILE * f = fopen (fname, "r");
FAISS_THROW_IF_NOT_MSG (f, "cannot open proc status file");
size_t sz = 0;
for (;;) {
char buf [256];
if (!fgets (buf, 256, f)) break;
if (sscanf (buf, "VmRSS: %ld kB", &sz) == 1) break;
}
fclose (f);
return sz;
}
#elif __APPLE__
size_t get_mem_usage_kb ()
{
fprintf(stderr, "WARN: get_mem_usage_kb not implemented on the mac\n");
return 0;
}
#endif
/**************************************************
* Random data generation functions
**************************************************/
RandomGenerator::RandomGenerator (long seed)
: mt((unsigned int)seed) {}
int RandomGenerator::rand_int ()
{
return mt() & 0x7fffffff;
}
long RandomGenerator::rand_long ()
{
return long(rand_int()) | long(rand_int()) << 31;
}
int RandomGenerator::rand_int (int max)
{
return mt() % max;
}
float RandomGenerator::rand_float ()
{
return mt() / float(mt.max());
}
double RandomGenerator::rand_double ()
{
return mt() / double(mt.max());
}
/***********************************************************************
* Random functions in this C file only exist because Torch
* counterparts are slow and not multi-threaded. Typical use is for
* more than 1-100 billion values. */
/* Generate a set of random floating point values such that x[i] in [0,1]
multi-threading. For this reason, we rely on re-entreant functions. */
void float_rand (float * x, size_t n, long seed)
{
// only try to parallelize on large enough arrays
const size_t nblock = n < 1024 ? 1 : 1024;
RandomGenerator rng0 (seed);
int a0 = rng0.rand_int (), b0 = rng0.rand_int ();
#pragma omp parallel for
for (size_t j = 0; j < nblock; j++) {
RandomGenerator rng (a0 + j * b0);
const size_t istart = j * n / nblock;
const size_t iend = (j + 1) * n / nblock;
for (size_t i = istart; i < iend; i++)
x[i] = rng.rand_float ();
}
}
void float_randn (float * x, size_t n, long seed)
{
// only try to parallelize on large enough arrays
const size_t nblock = n < 1024 ? 1 : 1024;
RandomGenerator rng0 (seed);
int a0 = rng0.rand_int (), b0 = rng0.rand_int ();
#pragma omp parallel for
for (size_t j = 0; j < nblock; j++) {
RandomGenerator rng (a0 + j * b0);
double a = 0, b = 0, s = 0;
int state = 0; /* generate two number per "do-while" loop */
const size_t istart = j * n / nblock;
const size_t iend = (j + 1) * n / nblock;
for (size_t i = istart; i < iend; i++) {
/* Marsaglia's method (see Knuth) */
if (state == 0) {
do {
a = 2.0 * rng.rand_double () - 1;
b = 2.0 * rng.rand_double () - 1;
s = a * a + b * b;
} while (s >= 1.0);
x[i] = a * sqrt(-2.0 * log(s) / s);
}
else
x[i] = b * sqrt(-2.0 * log(s) / s);
state = 1 - state;
}
}
}
/* Integer versions */
void long_rand (long * x, size_t n, long seed)
{
// only try to parallelize on large enough arrays
const size_t nblock = n < 1024 ? 1 : 1024;
RandomGenerator rng0 (seed);
int a0 = rng0.rand_int (), b0 = rng0.rand_int ();
#pragma omp parallel for
for (size_t j = 0; j < nblock; j++) {
RandomGenerator rng (a0 + j * b0);
const size_t istart = j * n / nblock;
const size_t iend = (j + 1) * n / nblock;
for (size_t i = istart; i < iend; i++)
x[i] = rng.rand_long ();
}
}
void rand_perm (int *perm, size_t n, long seed)
{
for (size_t i = 0; i < n; i++) perm[i] = i;
RandomGenerator rng (seed);
for (size_t i = 0; i + 1 < n; i++) {
int i2 = i + rng.rand_int (n - i);
std::swap(perm[i], perm[i2]);
}
}
void byte_rand (uint8_t * x, size_t n, long seed)
{
// only try to parallelize on large enough arrays
const size_t nblock = n < 1024 ? 1 : 1024;
RandomGenerator rng0 (seed);
int a0 = rng0.rand_int (), b0 = rng0.rand_int ();
#pragma omp parallel for
for (size_t j = 0; j < nblock; j++) {
RandomGenerator rng (a0 + j * b0);
const size_t istart = j * n / nblock;
const size_t iend = (j + 1) * n / nblock;
size_t i;
for (i = istart; i < iend; i++)
x[i] = rng.rand_long ();
}
}
void reflection (const float * __restrict u,
float * __restrict x,
size_t n, size_t d, size_t nu)
{
size_t i, j, l;
for (i = 0; i < n; i++) {
const float * up = u;
for (l = 0; l < nu; l++) {
float ip1 = 0, ip2 = 0;
for (j = 0; j < d; j+=2) {
ip1 += up[j] * x[j];
ip2 += up[j+1] * x[j+1];
}
float ip = 2 * (ip1 + ip2);
for (j = 0; j < d; j++)
x[j] -= ip * up[j];
up += d;
}
x += d;
}
}
/* Reference implementation (slower) */
void reflection_ref (const float * u, float * x, size_t n, size_t d, size_t nu)
{
size_t i, j, l;
for (i = 0; i < n; i++) {
const float * up = u;
for (l = 0; l < nu; l++) {
double ip = 0;
for (j = 0; j < d; j++)
ip += up[j] * x[j];
ip *= 2;
for (j = 0; j < d; j++)
x[j] -= ip * up[j];
up += d;
}
x += d;
}
}
/***************************************************************************
* Matrix/vector ops
***************************************************************************/
/* Compute the inner product between a vector x and
a set of ny vectors y.
These functions are not intended to replace BLAS matrix-matrix, as they
would be significantly less efficient in this case. */
void fvec_inner_products_ny (float * ip,
const float * x,
const float * y,
size_t d, size_t ny)
{
// Not sure which one is fastest
#if 0
{
FINTEGER di = d;
FINTEGER nyi = ny;
float one = 1.0, zero = 0.0;
FINTEGER onei = 1;
sgemv_ ("T", &di, &nyi, &one, y, &di, x, &onei, &zero, ip, &onei);
}
#endif
for (size_t i = 0; i < ny; i++) {
ip[i] = fvec_inner_product (x, y, d);
y += d;
}
}
/* Compute the L2 norm of a set of nx vectors */
void fvec_norms_L2 (float * __restrict nr,
const float * __restrict x,
size_t d, size_t nx)
{
#pragma omp parallel for
for (size_t i = 0; i < nx; i++) {
nr[i] = sqrtf (fvec_norm_L2sqr (x + i * d, d));
}
}
void fvec_norms_L2sqr (float * __restrict nr,
const float * __restrict x,
size_t d, size_t nx)
{
#pragma omp parallel for
for (size_t i = 0; i < nx; i++)
nr[i] = fvec_norm_L2sqr (x + i * d, d);
}
void fvec_renorm_L2 (size_t d, size_t nx, float * __restrict x)
{
#pragma omp parallel for
for (size_t i = 0; i < nx; i++) {
float * __restrict xi = x + i * d;
float nr = fvec_norm_L2sqr (xi, d);
if (nr > 0) {
size_t j;
const float inv_nr = 1.0 / sqrtf (nr);
for (j = 0; j < d; j++)
xi[j] *= inv_nr;
}
}
}
/***************************************************************************
* KNN functions
***************************************************************************/
/* Find the nearest neighbors for nx queries in a set of ny vectors */
static void knn_inner_product_sse (const float * x,
const float * y,
size_t d, size_t nx, size_t ny,
float_minheap_array_t * res)
{
size_t k = res->k;
#pragma omp parallel for
for (size_t i = 0; i < nx; i++) {
const float * x_i = x + i * d;
const float * y_j = y;
float * __restrict simi = res->get_val(i);
long * __restrict idxi = res->get_ids (i);
minheap_heapify (k, simi, idxi);
for (size_t j = 0; j < ny; j++) {
float ip = fvec_inner_product (x_i, y_j, d);
if (ip > simi[0]) {
minheap_pop (k, simi, idxi);
minheap_push (k, simi, idxi, ip, j);
}
y_j += d;
}
minheap_reorder (k, simi, idxi);
}
}
static void knn_L2sqr_sse (
const float * x,
const float * y,
size_t d, size_t nx, size_t ny,
float_maxheap_array_t * res)
{
size_t k = res->k;
#pragma omp parallel for
for (size_t i = 0; i < nx; i++) {
const float * x_i = x + i * d;
const float * y_j = y;
size_t j;
float * __restrict simi = res->get_val(i);
long * __restrict idxi = res->get_ids (i);
maxheap_heapify (k, simi, idxi);
for (j = 0; j < ny; j++) {
float disij = fvec_L2sqr (x_i, y_j, d);
if (disij < simi[0]) {
maxheap_pop (k, simi, idxi);
maxheap_push (k, simi, idxi, disij, j);
}
y_j += d;
}
maxheap_reorder (k, simi, idxi);
}
}
/** Find the nearest neighbors for nx queries in a set of ny vectors */
static void knn_inner_product_blas (
const float * x,
const float * y,
size_t d, size_t nx, size_t ny,
float_minheap_array_t * res)
{
res->heapify ();
// BLAS does not like empty matrices
if (nx == 0 || ny == 0) return;
/* block sizes */
const size_t bs_x = 4096, bs_y = 1024;
// const size_t bs_x = 16, bs_y = 16;
float *ip_block = new float[bs_x * bs_y];
for (size_t i0 = 0; i0 < nx; i0 += bs_x) {
size_t i1 = i0 + bs_x;
if(i1 > nx) i1 = nx;
for (size_t j0 = 0; j0 < ny; j0 += bs_y) {
size_t j1 = j0 + bs_y;
if (j1 > ny) j1 = ny;
/* compute the actual dot products */
{
float one = 1, zero = 0;
FINTEGER nyi = j1 - j0, nxi = i1 - i0, di = d;
sgemm_ ("Transpose", "Not transpose", &nyi, &nxi, &di, &one,
y + j0 * d, &di,
x + i0 * d, &di, &zero,
ip_block, &nyi);
}
/* collect maxima */
res->addn (j1 - j0, ip_block, j0, i0, i1 - i0);
}
}
delete [] ip_block;
res->reorder ();
}
// distance correction is an operator that can be applied to transform
// the distances
template<class DistanceCorrection>
static void knn_L2sqr_blas (const float * x,
const float * y,
size_t d, size_t nx, size_t ny,
float_maxheap_array_t * res,
const DistanceCorrection &corr)
{
res->heapify ();
// BLAS does not like empty matrices
if (nx == 0 || ny == 0) return;
size_t k = res->k;
/* block sizes */
const size_t bs_x = 4096, bs_y = 1024;
// const size_t bs_x = 16, bs_y = 16;
float *ip_block = new float[bs_x * bs_y];
float *x_norms = new float[nx];
fvec_norms_L2sqr (x_norms, x, d, nx);
float *y_norms = new float[ny];
fvec_norms_L2sqr (y_norms, y, d, ny);
for (size_t i0 = 0; i0 < nx; i0 += bs_x) {
size_t i1 = i0 + bs_x;
if(i1 > nx) i1 = nx;
for (size_t j0 = 0; j0 < ny; j0 += bs_y) {
size_t j1 = j0 + bs_y;
if (j1 > ny) j1 = ny;
/* compute the actual dot products */
{
float one = 1, zero = 0;
FINTEGER nyi = j1 - j0, nxi = i1 - i0, di = d;
sgemm_ ("Transpose", "Not transpose", &nyi, &nxi, &di, &one,
y + j0 * d, &di,
x + i0 * d, &di, &zero,
ip_block, &nyi);
}
/* collect minima */
#pragma omp parallel for
for (size_t i = i0; i < i1; i++) {
float * __restrict simi = res->get_val(i);
long * __restrict idxi = res->get_ids (i);
const float *ip_line = ip_block + (i - i0) * (j1 - j0);
for (size_t j = j0; j < j1; j++) {
float ip = *ip_line++;
float dis = x_norms[i] + y_norms[j] - 2 * ip;
// negative values can occur for identical vectors
// due to roundoff errors
if (dis < 0) dis = 0;
dis = corr (dis, i, j);
if (dis < simi[0]) {
maxheap_pop (k, simi, idxi);
maxheap_push (k, simi, idxi, dis, j);
}
}
}
}
}
res->reorder ();
delete [] ip_block;
delete [] x_norms;
delete [] y_norms;
}
/*******************************************************
* KNN driver functions
*******************************************************/
int distance_compute_blas_threshold = 20;
void knn_inner_product (const float * x,
const float * y,
size_t d, size_t nx, size_t ny,
float_minheap_array_t * res)
{
if (d % 4 == 0 && nx < distance_compute_blas_threshold) {
knn_inner_product_sse (x, y, d, nx, ny, res);
} else {
knn_inner_product_blas (x, y, d, nx, ny, res);
}
}
struct NopDistanceCorrection {
float operator()(float dis, size_t /*qno*/, size_t /*bno*/) const {
return dis;
}
};
void knn_L2sqr (const float * x,
const float * y,
size_t d, size_t nx, size_t ny,
float_maxheap_array_t * res)
{
if (d % 4 == 0 && nx < distance_compute_blas_threshold) {
knn_L2sqr_sse (x, y, d, nx, ny, res);
} else {
NopDistanceCorrection nop;
knn_L2sqr_blas (x, y, d, nx, ny, res, nop);
}
}
struct BaseShiftDistanceCorrection {
const float *base_shift;
float operator()(float dis, size_t /*qno*/, size_t bno) const {
return dis - base_shift[bno];
}
};
void knn_L2sqr_base_shift (
const float * x,
const float * y,
size_t d, size_t nx, size_t ny,
float_maxheap_array_t * res,
const float *base_shift)
{
BaseShiftDistanceCorrection corr = {base_shift};
knn_L2sqr_blas (x, y, d, nx, ny, res, corr);
}
/***************************************************************************
* compute a subset of distances
***************************************************************************/
/* compute the inner product between x and a subset y of ny vectors,
whose indices are given by idy. */
void fvec_inner_products_by_idx (float * __restrict ip,
const float * x,
const float * y,
const long * __restrict ids, /* for y vecs */
size_t d, size_t nx, size_t ny)
{
#pragma omp parallel for
for (size_t j = 0; j < nx; j++) {
const long * __restrict idsj = ids + j * ny;
const float * xj = x + j * d;
float * __restrict ipj = ip + j * ny;
for (size_t i = 0; i < ny; i++) {
if (idsj[i] < 0)
continue;
ipj[i] = fvec_inner_product (xj, y + d * idsj[i], d);
}
}
}
/* compute the inner product between x and a subset y of ny vectors,
whose indices are given by idy. */
void fvec_L2sqr_by_idx (float * __restrict dis,
const float * x,
const float * y,
const long * __restrict ids, /* ids of y vecs */
size_t d, size_t nx, size_t ny)
{
#pragma omp parallel for
for (size_t j = 0; j < nx; j++) {
const long * __restrict idsj = ids + j * ny;
const float * xj = x + j * d;
float * __restrict disj = dis + j * ny;
for (size_t i = 0; i < ny; i++) {
if (idsj[i] < 0)
continue;
disj[i] = fvec_L2sqr (xj, y + d * idsj[i], d);
}
}
}
/* Find the nearest neighbors for nx queries in a set of ny vectors
indexed by ids. May be useful for re-ranking a pre-selected vector list */
void knn_inner_products_by_idx (const float * x,
const float * y,
const long * ids,
size_t d, size_t nx, size_t ny,
float_minheap_array_t * res)
{
size_t k = res->k;
#pragma omp parallel for
for (size_t i = 0; i < nx; i++) {
const float * x_ = x + i * d;
const long * idsi = ids + i * ny;
size_t j;
float * __restrict simi = res->get_val(i);
long * __restrict idxi = res->get_ids (i);
minheap_heapify (k, simi, idxi);
for (j = 0; j < ny; j++) {
if (idsi[j] < 0) break;
float ip = fvec_inner_product (x_, y + d * idsi[j], d);
if (ip > simi[0]) {
minheap_pop (k, simi, idxi);
minheap_push (k, simi, idxi, ip, idsi[j]);
}
}
minheap_reorder (k, simi, idxi);
}
}
void knn_L2sqr_by_idx (const float * x,
const float * y,
const long * __restrict ids,
size_t d, size_t nx, size_t ny,
float_maxheap_array_t * res)
{
size_t k = res->k;
#pragma omp parallel for
for (size_t i = 0; i < nx; i++) {
const float * x_ = x + i * d;
const long * __restrict idsi = ids + i * ny;
float * __restrict simi = res->get_val(i);
long * __restrict idxi = res->get_ids (i);
maxheap_heapify (res->k, simi, idxi);
for (size_t j = 0; j < ny; j++) {
float disij = fvec_L2sqr (x_, y + d * idsi[j], d);
if (disij < simi[0]) {
maxheap_pop (k, simi, idxi);
maxheap_push (k, simi, idxi, disij, idsi[j]);
}
}
maxheap_reorder (res->k, simi, idxi);
}
}
/***************************************************************************
* Range search
***************************************************************************/
/** Find the nearest neighbors for nx queries in a set of ny vectors
* compute_l2 = compute pairwise squared L2 distance rather than inner prod
*/
template <bool compute_l2>
static void range_search_blas (
const float * x,
const float * y,
size_t d, size_t nx, size_t ny,
float radius,
RangeSearchResult *result)
{
// BLAS does not like empty matrices
if (nx == 0 || ny == 0) return;
/* block sizes */
const size_t bs_x = 4096, bs_y = 1024;
// const size_t bs_x = 16, bs_y = 16;
float *ip_block = new float[bs_x * bs_y];
float *x_norms = nullptr, *y_norms = nullptr;
if (compute_l2) {
x_norms = new float[nx];
fvec_norms_L2sqr (x_norms, x, d, nx);
y_norms = new float[ny];
fvec_norms_L2sqr (y_norms, y, d, ny);
}
std::vector <RangeSearchPartialResult *> partial_results;
for (size_t j0 = 0; j0 < ny; j0 += bs_y) {
size_t j1 = j0 + bs_y;
if (j1 > ny) j1 = ny;
RangeSearchPartialResult * pres = new RangeSearchPartialResult (result);
partial_results.push_back (pres);
for (size_t i0 = 0; i0 < nx; i0 += bs_x) {
size_t i1 = i0 + bs_x;
if(i1 > nx) i1 = nx;
/* compute the actual dot products */
{
float one = 1, zero = 0;
FINTEGER nyi = j1 - j0, nxi = i1 - i0, di = d;
sgemm_ ("Transpose", "Not transpose", &nyi, &nxi, &di, &one,
y + j0 * d, &di,
x + i0 * d, &di, &zero,
ip_block, &nyi);
}
for (size_t i = i0; i < i1; i++) {
const float *ip_line = ip_block + (i - i0) * (j1 - j0);
RangeSearchPartialResult::QueryResult & qres =
pres->new_result (i);
for (size_t j = j0; j < j1; j++) {
float ip = *ip_line++;
if (compute_l2) {
float dis = x_norms[i] + y_norms[j] - 2 * ip;
if (dis < radius) {
qres.add (dis, j);
}
} else {
if (ip > radius) {
qres.add (ip, j);
}
}
}
}
}
}
delete [] ip_block;
delete [] x_norms;
delete [] y_norms;
{ // merge the partial results
int npres = partial_results.size();
// count
for (size_t i = 0; i < nx; i++) {
for (int j = 0; j < npres; j++)
result->lims[i] += partial_results[j]->queries[i].nres;
}
result->do_allocation ();
for (int j = 0; j < npres; j++) {
partial_results[j]->set_result (true);
delete partial_results[j];
}
// reset the limits
for (size_t i = nx; i > 0; i--) {
result->lims [i] = result->lims [i - 1];
}
result->lims [0] = 0;
}
}
template <bool compute_l2>
static void range_search_sse (const float * x,
const float * y,
size_t d, size_t nx, size_t ny,
float radius,
RangeSearchResult *res)
{
FAISS_THROW_IF_NOT (d % 4 == 0);
#pragma omp parallel
{
RangeSearchPartialResult pres (res);
#pragma omp for
for (size_t i = 0; i < nx; i++) {
const float * x_ = x + i * d;
const float * y_ = y;
size_t j;
RangeSearchPartialResult::QueryResult & qres =
pres.new_result (i);
for (j = 0; j < ny; j++) {
if (compute_l2) {
float disij = fvec_L2sqr (x_, y_, d);
if (disij < radius) {
qres.add (disij, j);
}
} else {
float ip = fvec_inner_product (x_, y_, d);
if (ip > radius) {
qres.add (ip, j);
}
}
y_ += d;
}
}
pres.finalize ();
}
}
void range_search_L2sqr (
const float * x,
const float * y,
size_t d, size_t nx, size_t ny,
float radius,
RangeSearchResult *res)
{
if (d % 4 == 0 && nx < distance_compute_blas_threshold) {
range_search_sse<true> (x, y, d, nx, ny, radius, res);
} else {
range_search_blas<true> (x, y, d, nx, ny, radius, res);
}
}
void range_search_inner_product (
const float * x,
const float * y,
size_t d, size_t nx, size_t ny,
float radius,
RangeSearchResult *res)
{
if (d % 4 == 0 && nx < distance_compute_blas_threshold) {
range_search_sse<false> (x, y, d, nx, ny, radius, res);
} else {
range_search_blas<false> (x, y, d, nx, ny, radius, res);
}
}
/***************************************************************************
* Some matrix manipulation functions
***************************************************************************/
/* This function exists because the Torch counterpart is extremly slow
(not multi-threaded + unexpected overhead even in single thread).
It is here to implement the usual property |x-y|^2=|x|^2+|y|^2-2<x|y> */
void inner_product_to_L2sqr (float * __restrict dis,
const float * nr1,
const float * nr2,
size_t n1, size_t n2)
{
#pragma omp parallel for
for (size_t j = 0 ; j < n1 ; j++) {
float * disj = dis + j * n2;
for (size_t i = 0 ; i < n2 ; i++)
disj[i] = nr1[j] + nr2[i] - 2 * disj[i];
}
}
void matrix_qr (int m, int n, float *a)
{
FAISS_THROW_IF_NOT (m >= n);
FINTEGER mi = m, ni = n, ki = mi < ni ? mi : ni;
std::vector<float> tau (ki);
FINTEGER lwork = -1, info;
float work_size;
sgeqrf_ (&mi, &ni, a, &mi, tau.data(),
&work_size, &lwork, &info);
lwork = size_t(work_size);
std::vector<float> work (lwork);
sgeqrf_ (&mi, &ni, a, &mi,
tau.data(), work.data(), &lwork, &info);
sorgqr_ (&mi, &ni, &ki, a, &mi, tau.data(),
work.data(), &lwork, &info);
}
void pairwise_L2sqr (long d,
long nq, const float *xq,
long nb, const float *xb,
float *dis,
long ldq, long ldb, long ldd)
{
if (nq == 0 || nb == 0) return;
if (ldq == -1) ldq = d;
if (ldb == -1) ldb = d;
if (ldd == -1) ldd = nb;
// store in beginning of distance matrix to avoid malloc
float *b_norms = dis;
#pragma omp parallel for
for (long i = 0; i < nb; i++)
b_norms [i] = fvec_norm_L2sqr (xb + i * ldb, d);
#pragma omp parallel for
for (long i = 1; i < nq; i++) {
float q_norm = fvec_norm_L2sqr (xq + i * ldq, d);
for (long j = 0; j < nb; j++)
dis[i * ldd + j] = q_norm + b_norms [j];
}
{
float q_norm = fvec_norm_L2sqr (xq, d);
for (long j = 0; j < nb; j++)
dis[j] += q_norm;
}
{
FINTEGER nbi = nb, nqi = nq, di = d, ldqi = ldq, ldbi = ldb, lddi = ldd;
float one = 1.0, minus_2 = -2.0;
sgemm_ ("Transposed", "Not transposed",
&nbi, &nqi, &di,
&minus_2,
xb, &ldbi,
xq, &ldqi,
&one, dis, &lddi);
}
}
/***************************************************************************
* Kmeans subroutine
***************************************************************************/
// a bit above machine epsilon for float16
#define EPS (1 / 1024.)
/* For k-means, compute centroids given assignment of vectors to centroids */
int km_update_centroids (const float * x,
float * centroids,
long * assign,
size_t d, size_t k, size_t n,
size_t k_frozen)
{
k -= k_frozen;
centroids += k_frozen * d;
std::vector<size_t> hassign(k);
memset (centroids, 0, sizeof(*centroids) * d * k);
#pragma omp parallel
{
int nt = omp_get_num_threads();
int rank = omp_get_thread_num();
// this thread is taking care of centroids c0:c1
size_t c0 = (k * rank) / nt;
size_t c1 = (k * (rank + 1)) / nt;
const float *xi = x;
size_t nacc = 0;
for (size_t i = 0; i < n; i++) {
long ci = assign[i];
assert (ci >= 0 && ci < k + k_frozen);
ci -= k_frozen;
if (ci >= c0 && ci < c1) {
float * c = centroids + ci * d;
hassign[ci]++;
for (size_t j = 0; j < d; j++)
c[j] += xi[j];
nacc++;
}
xi += d;
}
}
#pragma omp parallel for
for (size_t ci = 0; ci < k; ci++) {
float * c = centroids + ci * d;
float ni = (float) hassign[ci];
if (ni != 0) {
for (size_t j = 0; j < d; j++)
c[j] /= ni;
}
}
/* Take care of void clusters */
size_t nsplit = 0;
RandomGenerator rng (1234);
for (size_t ci = 0; ci < k; ci++) {
if (hassign[ci] == 0) { /* need to redefine a centroid */
size_t cj;
for (cj = 0; 1; cj = (cj + 1) % k) {
/* probability to pick this cluster for split */
float p = (hassign[cj] - 1.0) / (float) (n - k);
float r = rng.rand_float ();
if (r < p) {
break; /* found our cluster to be split */
}
}
memcpy (centroids+ci*d, centroids+cj*d, sizeof(*centroids) * d);
/* small symmetric pertubation. Much better than */
for (size_t j = 0; j < d; j++) {
if (j % 2 == 0) {
centroids[ci * d + j] *= 1 + EPS;
centroids[cj * d + j] *= 1 - EPS;
} else {
centroids[ci * d + j] *= 1 - EPS;
centroids[cj * d + j] *= 1 + EPS;
}
}
/* assume even split of the cluster */
hassign[ci] = hassign[cj] / 2;
hassign[cj] -= hassign[ci];
nsplit++;
}
}
return nsplit;
}
#undef EPS
/***************************************************************************
* Result list routines
***************************************************************************/
void ranklist_handle_ties (int k, long *idx, const float *dis)
{
float prev_dis = -1e38;
int prev_i = -1;
for (int i = 0; i < k; i++) {
if (dis[i] != prev_dis) {
if (i > prev_i + 1) {
// sort between prev_i and i - 1
std::sort (idx + prev_i, idx + i);
}
prev_i = i;
prev_dis = dis[i];
}
}
}
size_t merge_result_table_with (size_t n, size_t k,
long *I0, float *D0,
const long *I1, const float *D1,
bool keep_min,
long translation)
{
size_t n1 = 0;
#pragma omp parallel reduction(+:n1)
{
std::vector<long> tmpI (k);
std::vector<float> tmpD (k);
#pragma omp for
for (size_t i = 0; i < n; i++) {
long *lI0 = I0 + i * k;
float *lD0 = D0 + i * k;
const long *lI1 = I1 + i * k;
const float *lD1 = D1 + i * k;
size_t r0 = 0;
size_t r1 = 0;
if (keep_min) {
for (size_t j = 0; j < k; j++) {
if (lI0[r0] >= 0 && lD0[r0] < lD1[r1]) {
tmpD[j] = lD0[r0];
tmpI[j] = lI0[r0];
r0++;
} else if (lD1[r1] >= 0) {
tmpD[j] = lD1[r1];
tmpI[j] = lI1[r1] + translation;
r1++;
} else { // both are NaNs
tmpD[j] = NAN;
tmpI[j] = -1;
}
}
} else {
for (size_t j = 0; j < k; j++) {
if (lI0[r0] >= 0 && lD0[r0] > lD1[r1]) {
tmpD[j] = lD0[r0];
tmpI[j] = lI0[r0];
r0++;
} else if (lD1[r1] >= 0) {
tmpD[j] = lD1[r1];
tmpI[j] = lI1[r1] + translation;
r1++;
} else { // both are NaNs
tmpD[j] = NAN;
tmpI[j] = -1;
}
}
}
n1 += r1;
memcpy (lD0, tmpD.data(), sizeof (lD0[0]) * k);
memcpy (lI0, tmpI.data(), sizeof (lI0[0]) * k);
}
}
return n1;
}
size_t ranklist_intersection_size (size_t k1, const long *v1,
size_t k2, const long *v2_in)
{
if (k2 > k1) return ranklist_intersection_size (k2, v2_in, k1, v1);
long *v2 = new long [k2];
memcpy (v2, v2_in, sizeof (long) * k2);
std::sort (v2, v2 + k2);
{ // de-dup v2
long prev = -1;
size_t wp = 0;
for (size_t i = 0; i < k2; i++) {
if (v2 [i] != prev) {
v2[wp++] = prev = v2 [i];
}
}
k2 = wp;
}
const long seen_flag = 1L << 60;
size_t count = 0;
for (size_t i = 0; i < k1; i++) {
long q = v1 [i];
size_t i0 = 0, i1 = k2;
while (i0 + 1 < i1) {
size_t imed = (i1 + i0) / 2;
long piv = v2 [imed] & ~seen_flag;
if (piv <= q) i0 = imed;
else i1 = imed;
}
if (v2 [i0] == q) {
count++;
v2 [i0] |= seen_flag;
}
}
delete [] v2;
return count;
}
double imbalance_factor (int k, const int *hist) {
double tot = 0, uf = 0;
for (int i = 0 ; i < k ; i++) {
tot += hist[i];
uf += hist[i] * (double) hist[i];
}
uf = uf * k / (tot * tot);
return uf;
}
double imbalance_factor (int n, int k, const long *assign) {
std::vector<int> hist(k, 0);
for (int i = 0; i < n; i++) {
hist[assign[i]]++;
}
return imbalance_factor (k, hist.data());
}
int ivec_hist (size_t n, const int * v, int vmax, int *hist) {
memset (hist, 0, sizeof(hist[0]) * vmax);
int nout = 0;
while (n--) {
if (v[n] < 0 || v[n] >= vmax) nout++;
else hist[v[n]]++;
}
return nout;
}
void bincode_hist(size_t n, size_t nbits, const uint8_t *codes, int *hist)
{
FAISS_THROW_IF_NOT (nbits % 8 == 0);
size_t d = nbits / 8;
std::vector<int> accu(d * 256);
const uint8_t *c = codes;
for (size_t i = 0; i < n; i++)
for(int j = 0; j < d; j++)
accu[j * 256 + *c++]++;
memset (hist, 0, sizeof(*hist) * nbits);
for (int i = 0; i < d; i++) {
const int *ai = accu.data() + i * 256;
int * hi = hist + i * 8;
for (int j = 0; j < 256; j++)
for (int k = 0; k < 8; k++)
if ((j >> k) & 1)
hi[k] += ai[j];
}
}
size_t ivec_checksum (size_t n, const int *a)
{
size_t cs = 112909;
while (n--) cs = cs * 65713 + a[n] * 1686049;
return cs;
}
namespace {
struct ArgsortComparator {
const float *vals;
bool operator() (const size_t a, const size_t b) const {
return vals[a] < vals[b];
}
};
struct SegmentS {
size_t i0; // begin pointer in the permutation array
size_t i1; // end
size_t len() const {
return i1 - i0;
}
};
// see https://en.wikipedia.org/wiki/Merge_algorithm#Parallel_merge
// extended to > 1 merge thread
// merges 2 ranges that should be consecutive on the source into
// the union of the two on the destination
template<typename T>
void parallel_merge (const T *src, T *dst,
SegmentS &s1, SegmentS & s2, int nt,
const ArgsortComparator & comp) {
if (s2.len() > s1.len()) { // make sure that s1 larger than s2
std::swap(s1, s2);
}
// compute sub-ranges for each thread
SegmentS s1s[nt], s2s[nt], sws[nt];
s2s[0].i0 = s2.i0;
s2s[nt - 1].i1 = s2.i1;
// not sure parallel actually helps here
#pragma omp parallel for num_threads(nt)
for (int t = 0; t < nt; t++) {
s1s[t].i0 = s1.i0 + s1.len() * t / nt;
s1s[t].i1 = s1.i0 + s1.len() * (t + 1) / nt;
if (t + 1 < nt) {
T pivot = src[s1s[t].i1];
size_t i0 = s2.i0, i1 = s2.i1;
while (i0 + 1 < i1) {
size_t imed = (i1 + i0) / 2;
if (comp (pivot, src[imed])) {i1 = imed; }
else {i0 = imed; }
}
s2s[t].i1 = s2s[t + 1].i0 = i1;
}
}
s1.i0 = std::min(s1.i0, s2.i0);
s1.i1 = std::max(s1.i1, s2.i1);
s2 = s1;
sws[0].i0 = s1.i0;
for (int t = 0; t < nt; t++) {
sws[t].i1 = sws[t].i0 + s1s[t].len() + s2s[t].len();
if (t + 1 < nt) {
sws[t + 1].i0 = sws[t].i1;
}
}
assert(sws[nt - 1].i1 == s1.i1);
// do the actual merging
#pragma omp parallel for num_threads(nt)
for (int t = 0; t < nt; t++) {
SegmentS sw = sws[t];
SegmentS s1t = s1s[t];
SegmentS s2t = s2s[t];
if (s1t.i0 < s1t.i1 && s2t.i0 < s2t.i1) {
for (;;) {
// assert (sw.len() == s1t.len() + s2t.len());
if (comp(src[s1t.i0], src[s2t.i0])) {
dst[sw.i0++] = src[s1t.i0++];
if (s1t.i0 == s1t.i1) break;
} else {
dst[sw.i0++] = src[s2t.i0++];
if (s2t.i0 == s2t.i1) break;
}
}
}
if (s1t.len() > 0) {
assert(s1t.len() == sw.len());
memcpy(dst + sw.i0, src + s1t.i0, s1t.len() * sizeof(dst[0]));
} else if (s2t.len() > 0) {
assert(s2t.len() == sw.len());
memcpy(dst + sw.i0, src + s2t.i0, s2t.len() * sizeof(dst[0]));
}
}
}
};
void fvec_argsort (size_t n, const float *vals,
size_t *perm)
{
for (size_t i = 0; i < n; i++) perm[i] = i;
ArgsortComparator comp = {vals};
std::sort (perm, perm + n, comp);
}
void fvec_argsort_parallel (size_t n, const float *vals,
size_t *perm)
{
size_t * perm2 = new size_t[n];
// 2 result tables, during merging, flip between them
size_t *permB = perm2, *permA = perm;
int nt = omp_get_max_threads();
{ // prepare correct permutation so that the result ends in perm
// at final iteration
int nseg = nt;
while (nseg > 1) {
nseg = (nseg + 1) / 2;
std::swap (permA, permB);
}
}
#pragma omp parallel
for (size_t i = 0; i < n; i++) permA[i] = i;
ArgsortComparator comp = {vals};
SegmentS segs[nt];
// independent sorts
#pragma omp parallel for
for (int t = 0; t < nt; t++) {
size_t i0 = t * n / nt;
size_t i1 = (t + 1) * n / nt;
SegmentS seg = {i0, i1};
std::sort (permA + seg.i0, permA + seg.i1, comp);
segs[t] = seg;
}
int prev_nested = omp_get_nested();
omp_set_nested(1);
int nseg = nt;
while (nseg > 1) {
int nseg1 = (nseg + 1) / 2;
int sub_nt = nseg % 2 == 0 ? nt : nt - 1;
int sub_nseg1 = nseg / 2;
#pragma omp parallel for num_threads(nseg1)
for (int s = 0; s < nseg; s += 2) {
if (s + 1 == nseg) { // otherwise isolated segment
memcpy(permB + segs[s].i0, permA + segs[s].i0,
segs[s].len() * sizeof(size_t));
} else {
int t0 = s * sub_nt / sub_nseg1;
int t1 = (s + 1) * sub_nt / sub_nseg1;
printf("merge %d %d, %d threads\n", s, s + 1, t1 - t0);
parallel_merge(permA, permB, segs[s], segs[s + 1],
t1 - t0, comp);
}
}
for (int s = 0; s < nseg; s += 2)
segs[s / 2] = segs[s];
nseg = nseg1;
std::swap (permA, permB);
}
assert (permA == perm);
omp_set_nested(prev_nested);
delete [] perm2;
}
const float *fvecs_maybe_subsample (
size_t d, size_t *n, size_t nmax, const float *x,
bool verbose, long seed)
{
if (*n <= nmax) return x; // nothing to do
size_t n2 = nmax;
if (verbose) {
printf (" Input training set too big (max size is %ld), sampling "
"%ld / %ld vectors\n", nmax, n2, *n);
}
std::vector<int> subset (*n);
rand_perm (subset.data (), *n, seed);
float *x_subset = new float[n2 * d];
for (long i = 0; i < n2; i++)
memcpy (&x_subset[i * d],
&x[subset[i] * size_t(d)],
sizeof (x[0]) * d);
*n = n2;
return x_subset;
}
void binary_to_real(size_t d, const uint8_t *x_in, float *x_out) {
for (size_t i = 0; i < d; ++i) {
x_out[i] = 2 * ((x_in[i >> 3] >> (i & 7)) & 1) - 1;
}
}
void real_to_binary(size_t d, const float *x_in, uint8_t *x_out) {
for (size_t i = 0; i < d / 8; ++i) {
uint8_t b = 0;
for (int j = 0; j < 8; ++j) {
if (x_in[8 * i + j] > 0) {
b |= (1 << j);
}
}
x_out[i] = b;
}
}
} // namespace faiss
faiss::RandomGenerator
random generator that can be used in multithreaded contexts
Definition: utils.h:48
faiss::km_update_centroids
int km_update_centroids(const float *x, float *centroids, long *assign, size_t d, size_t k, size_t n, size_t k_frozen)
Definition: utils.cpp:1066
faiss::knn_L2sqr_base_shift
void knn_L2sqr_base_shift(const float *x, const float *y, size_t d, size_t nx, size_t ny, float_maxheap_array_t *res, const float *base_shift)
Definition: utils.cpp:653
faiss::fvec_L2sqr
float fvec_L2sqr(const float *x, const float *y, size_t d)
Squared L2 distance between two vectors.
Definition: utils_simd.cpp:502
faiss::bincode_hist
void bincode_hist(size_t n, size_t nbits, const uint8_t *codes, int *hist)
Definition: utils.cpp:1314
faiss::fvecs_maybe_subsample
const float * fvecs_maybe_subsample(size_t d, size_t *n, size_t nmax, const float *x, bool verbose, long seed)
Definition: utils.cpp:1528
faiss::ranklist_handle_ties
void ranklist_handle_ties(int k, long *idx, const float *dis)
Definition: utils.cpp:1160
faiss::RandomGenerator::rand_float
float rand_float()
between 0 and 1
Definition: utils.cpp:130
faiss::get_mem_usage_kb
size_t get_mem_usage_kb()
get current RSS usage in kB
faiss::ivec_hist
int ivec_hist(size_t n, const int *v, int vmax, int *hist)
compute histogram on v
Definition: utils.cpp:1303
faiss::merge_result_table_with
size_t merge_result_table_with(size_t n, size_t k, long *I0, float *D0, const long *I1, const float *D1, bool keep_min, long translation)
Definition: utils.cpp:1176
faiss::HeapArray
Definition: Heap.h:350
faiss::ranklist_intersection_size
size_t ranklist_intersection_size(size_t k1, const long *v1, size_t k2, const long *v2_in)
Definition: utils.cpp:1241
faiss::pairwise_L2sqr
void pairwise_L2sqr(long d, long nq, const float *xq, long nb, const float *xb, float *dis, long ldq, long ldb, long ldd)
Definition: utils.cpp:1009
faiss::range_search_inner_product
void range_search_inner_product(const float *x, const float *y, size_t d, size_t nx, size_t ny, float radius, RangeSearchResult *res)
same as range_search_L2sqr for the inner product similarity
Definition: utils.cpp:947
faiss::knn_inner_product
void knn_inner_product(const float *x, const float *y, size_t d, size_t nx, size_t ny, float_minheap_array_t *res)
Definition: utils.cpp:613
faiss::getmillisecs
double getmillisecs()
ms elapsed since some arbitrary epoch
Definition: utils.cpp:70
faiss::NopDistanceCorrection
Definition: utils.cpp:627
faiss::real_to_binary
void real_to_binary(size_t d, const float *x_in, uint8_t *x_out)
Definition: utils.cpp:1558
faiss::imbalance_factor
double imbalance_factor(int k, const int *hist)
same, takes a histogram as input
Definition: utils.cpp:1279
faiss::fvec_norm_L2sqr
float fvec_norm_L2sqr(const float *x, size_t d)
Definition: utils_simd.cpp:516
faiss::range_search_L2sqr
void range_search_L2sqr(const float *x, const float *y, size_t d, size_t nx, size_t ny, float radius, RangeSearchResult *res)
Definition: utils.cpp:932
faiss::matrix_qr
void matrix_qr(int m, int n, float *a)
Definition: utils.cpp:987
faiss::RangeSearchResult
Definition: AuxIndexStructures.h:31
faiss::ivec_checksum
size_t ivec_checksum(size_t n, const int *a)
compute a checksum on a table.
Definition: utils.cpp:1337
faiss::BaseShiftDistanceCorrection
Definition: utils.cpp:646
faiss::knn_L2sqr
void knn_L2sqr(const float *x, const float *y, size_t d, size_t nx, size_t ny, float_maxheap_array_t *res)
Definition: utils.cpp:633
faiss::binary_to_real
void binary_to_real(size_t d, const uint8_t *x_in, float *x_out)
Definition: utils.cpp:1552