westonpace commented on a change in pull request #12067:
URL: https://github.com/apache/arrow/pull/12067#discussion_r825225218
##########
File path: cpp/src/arrow/compute/exec/vector_hash_test.cc
##########
@@ -0,0 +1,234 @@
+// Licensed to the Apache Software Foundation (ASF) under one
Review comment:
This file should be named `key_hash_test.cc` as it is testing the code
in `key_hash.h` now.
##########
File path: cpp/src/arrow/compute/exec/vector_hash_test.cc
##########
@@ -0,0 +1,234 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#include <gmock/gmock-matchers.h>
+
+#include <chrono>
+#include <map>
+#include <set>
+#include "arrow/compute/exec/key_hash.h"
+#include "arrow/compute/exec/test_util.h"
+#include "arrow/compute/exec/util.h"
+#include "arrow/util/cpu_info.h"
+
+namespace arrow {
+namespace compute {
+
+void TestVectorHashImp(Random64Bit& random, bool use_32bit_hash, bool
use_varlen_input,
+ int min_length, int max_length) {
+ ARROW_DCHECK(use_varlen_input || min_length == max_length);
+
+ constexpr int min_num_unique = 100;
+ constexpr int max_num_unique = 1000;
+ constexpr int min_num_rows = 4000;
+ constexpr int max_num_rows = 64000;
+ int num_unique =
+ min_num_unique + (random.next() % (max_num_unique - min_num_unique + 1));
+ int num_rows = min_num_rows + (random.next() % (max_num_rows - min_num_rows
+ 1));
+
+ SCOPED_TRACE("num_bits = " + std::to_string(use_32bit_hash ? 32 : 64) +
+ " varlen = " + std::string(use_varlen_input ? "yes" : "no") +
+ " num_unique " + std::to_string(num_unique) + " num_rows " +
+ std::to_string(num_rows) + " min_length " +
std::to_string(min_length) +
+ " max_length " + std::to_string(max_length));
+
+ if (max_length == 1) {
+ num_unique &= 0x7f;
+ }
+
+ std::vector<uint32_t> unique_keys_offsets;
+ unique_keys_offsets.resize(num_unique + 1);
+ unique_keys_offsets[0] = 0;
+
+ const int num_bytes = unique_keys_offsets[num_unique];
+ std::vector<uint8_t> unique_keys;
+ unique_keys.resize(num_bytes);
+ std::set<std::string> unique_key_strings;
+ for (int i = 0; i < num_unique; ++i) {
+ for (;;) {
+ int next_length;
+ if (use_varlen_input) {
+ next_length = min_length + random.next() % (max_length - min_length +
1);
+ } else {
+ next_length = max_length;
+ }
+ unique_keys_offsets[i + 1] = unique_keys_offsets[i] + next_length;
Review comment:
A lot of the logic here is reinventing things we have in `BinaryBuilder`
We should probably use that class.
##########
File path: cpp/src/arrow/compute/exec/vector_hash_test.cc
##########
@@ -0,0 +1,234 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#include <gmock/gmock-matchers.h>
+
+#include <chrono>
+#include <map>
+#include <set>
+#include "arrow/compute/exec/key_hash.h"
+#include "arrow/compute/exec/test_util.h"
+#include "arrow/compute/exec/util.h"
+#include "arrow/util/cpu_info.h"
+
+namespace arrow {
+namespace compute {
+
+void TestVectorHashImp(Random64Bit& random, bool use_32bit_hash, bool
use_varlen_input,
+ int min_length, int max_length) {
+ ARROW_DCHECK(use_varlen_input || min_length == max_length);
+
+ constexpr int min_num_unique = 100;
+ constexpr int max_num_unique = 1000;
+ constexpr int min_num_rows = 4000;
+ constexpr int max_num_rows = 64000;
+ int num_unique =
+ min_num_unique + (random.next() % (max_num_unique - min_num_unique + 1));
+ int num_rows = min_num_rows + (random.next() % (max_num_rows - min_num_rows
+ 1));
+
+ SCOPED_TRACE("num_bits = " + std::to_string(use_32bit_hash ? 32 : 64) +
+ " varlen = " + std::string(use_varlen_input ? "yes" : "no") +
+ " num_unique " + std::to_string(num_unique) + " num_rows " +
+ std::to_string(num_rows) + " min_length " +
std::to_string(min_length) +
+ " max_length " + std::to_string(max_length));
+
+ if (max_length == 1) {
+ num_unique &= 0x7f;
+ }
+
+ std::vector<uint32_t> unique_keys_offsets;
+ unique_keys_offsets.resize(num_unique + 1);
+ unique_keys_offsets[0] = 0;
+
+ const int num_bytes = unique_keys_offsets[num_unique];
+ std::vector<uint8_t> unique_keys;
+ unique_keys.resize(num_bytes);
+ std::set<std::string> unique_key_strings;
+ for (int i = 0; i < num_unique; ++i) {
+ for (;;) {
+ int next_length;
+ if (use_varlen_input) {
+ next_length = min_length + random.next() % (max_length - min_length +
1);
+ } else {
+ next_length = max_length;
+ }
+ unique_keys_offsets[i + 1] = unique_keys_offsets[i] + next_length;
+ unique_keys.resize(unique_keys_offsets[i + 1]);
+ uint8_t* next_key = unique_keys.data() + unique_keys_offsets[i];
+
+ for (int iword = 0; iword < next_length /
static_cast<int>(sizeof(uint64_t));
+ ++iword) {
+ reinterpret_cast<uint64_t*>(next_key)[iword] = random.next();
+ }
+ if (next_length % sizeof(uint64_t) > 0) {
+ uint8_t* tail = next_key + next_length - (next_length %
sizeof(uint64_t));
+ for (int ibyte = 0; ibyte < (next_length %
static_cast<int>(sizeof(uint64_t)));
+ ++ibyte) {
+ tail[ibyte] = static_cast<uint8_t>(random.next() & 0xff);
+ }
+ }
+ std::string next_key_string =
+ std::string(reinterpret_cast<const char*>(next_key), next_length);
+ if (unique_key_strings.find(next_key_string) ==
unique_key_strings.end()) {
+ unique_key_strings.insert(next_key_string);
+ break;
+ }
+ }
+ }
+
+ std::vector<int> row_ids;
+ row_ids.resize(num_rows);
+ std::vector<uint8_t> keys;
+ std::vector<uint32_t> keys_offsets;
+ keys_offsets.resize(num_rows + 1);
+ keys_offsets[0] = 0;
+ for (int i = 0; i < num_rows; ++i) {
+ int row_id = random.next() % num_unique;
+ row_ids[i] = row_id;
+ int next_length = unique_keys_offsets[row_id + 1] -
unique_keys_offsets[row_id];
+ keys_offsets[i + 1] = keys_offsets[i] + next_length;
+ }
+ keys.resize(keys_offsets[num_rows]);
+ for (int i = 0; i < num_rows; ++i) {
+ int row_id = row_ids[i];
+ int next_length = keys_offsets[i + 1] - keys_offsets[i];
+ memcpy(keys.data() + keys_offsets[i],
+ unique_keys.data() + unique_keys_offsets[row_id], next_length);
+ }
+
+ constexpr int min_rows_for_timing = 1 << 23;
+ int num_repeats = static_cast<int>(bit_util::CeilDiv(min_rows_for_timing,
num_rows));
+#ifndef NDEBUG
+ num_repeats = 1;
+#endif
+
+ std::vector<uint32_t> hashes_scalar32;
+ std::vector<uint64_t> hashes_scalar64;
+ hashes_scalar32.resize(num_rows);
+ hashes_scalar64.resize(num_rows);
+ std::vector<uint32_t> hashes_simd32;
+ std::vector<uint64_t> hashes_simd64;
+ hashes_simd32.resize(num_rows);
+ hashes_simd64.resize(num_rows);
+
+ int64_t hardware_flags_scalar = 0LL;
+ int64_t hardware_flags_simd = ::arrow::internal::CpuInfo::AVX2;
+
+ constexpr int mini_batch_size = 1024;
+ std::vector<uint32_t> temp_buffer;
+ temp_buffer.resize(mini_batch_size * 4);
+
+ for (bool use_simd : {false, true}) {
+ for (int i = 0; i < num_repeats; ++i) {
+ if (use_32bit_hash) {
+ if (!use_varlen_input) {
+ Hashing32::hash_fixed(use_simd ? hardware_flags_simd :
hardware_flags_scalar,
+ /*combine_hashes=*/false, num_rows, max_length,
+ keys.data(),
+ use_simd ? hashes_simd32.data() :
hashes_scalar32.data(),
+ temp_buffer.data());
+ } else {
+ for (int first_row = 0; first_row < num_rows;) {
+ int batch_size_next = std::min(num_rows - first_row,
mini_batch_size);
+
+ Hashing32::hash_varlen(
+ use_simd ? hardware_flags_simd : hardware_flags_scalar,
+ /*combine_hashes=*/false, batch_size_next,
+ keys_offsets.data() + first_row, keys.data(),
+ (use_simd ? hashes_simd32.data() : hashes_scalar32.data()) +
first_row,
+ temp_buffer.data());
+
+ first_row += batch_size_next;
+ }
+ }
+ } else {
+ if (!use_varlen_input) {
+ Hashing64::hash_fixed(/*combine_hashes=*/false, num_rows, max_length,
+ keys.data(),
+ use_simd ? hashes_simd64.data() :
hashes_scalar64.data());
+ } else {
+ Hashing64::hash_varlen(
+ /*combine_hashes=*/false, num_rows, keys_offsets.data(),
keys.data(),
+ use_simd ? hashes_simd64.data() : hashes_scalar64.data());
+ }
+ }
+ }
+ }
+ if (use_32bit_hash) {
+ for (int i = 0; i < num_rows; ++i) {
+ hashes_scalar64[i] = hashes_scalar32[i];
+ hashes_simd64[i] = hashes_simd32[i];
+ }
+ }
+
+ // Verify that both scalar and AVX2 implementations give the same hashes
+ //
+ for (int i = 0; i < num_rows; ++i) {
+ if (hashes_scalar64[i] != hashes_simd64[i]) {
+ ARROW_DCHECK(false);
+ }
+ }
+
+ // Verify that the same key appearing multiple times generates the same hash
+ // each time. Measure the number of unique hashes and compare to the number
+ // of unique keys.
+ //
+ std::map<int, uint64_t> unique_key_to_hash;
+ std::set<uint64_t> unique_hashes;
+ for (int i = 0; i < num_rows; ++i) {
+ std::map<int, uint64_t>::iterator iter =
unique_key_to_hash.find(row_ids[i]);
+ if (iter == unique_key_to_hash.end()) {
+ unique_key_to_hash.insert(std::make_pair(row_ids[i],
hashes_scalar64[i]));
+ } else {
+ ARROW_DCHECK(iter->second == hashes_scalar64[i]);
Review comment:
We should use `ASSERT` instead of `DCHECK`
##########
File path: cpp/src/arrow/compute/exec/vector_hash_test.cc
##########
@@ -0,0 +1,234 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#include <gmock/gmock-matchers.h>
+
+#include <chrono>
+#include <map>
+#include <set>
+#include "arrow/compute/exec/key_hash.h"
+#include "arrow/compute/exec/test_util.h"
+#include "arrow/compute/exec/util.h"
+#include "arrow/util/cpu_info.h"
+
+namespace arrow {
+namespace compute {
+
+void TestVectorHashImp(Random64Bit& random, bool use_32bit_hash, bool
use_varlen_input,
+ int min_length, int max_length) {
+ ARROW_DCHECK(use_varlen_input || min_length == max_length);
+
+ constexpr int min_num_unique = 100;
+ constexpr int max_num_unique = 1000;
+ constexpr int min_num_rows = 4000;
+ constexpr int max_num_rows = 64000;
+ int num_unique =
+ min_num_unique + (random.next() % (max_num_unique - min_num_unique + 1));
+ int num_rows = min_num_rows + (random.next() % (max_num_rows - min_num_rows
+ 1));
+
+ SCOPED_TRACE("num_bits = " + std::to_string(use_32bit_hash ? 32 : 64) +
+ " varlen = " + std::string(use_varlen_input ? "yes" : "no") +
+ " num_unique " + std::to_string(num_unique) + " num_rows " +
+ std::to_string(num_rows) + " min_length " +
std::to_string(min_length) +
+ " max_length " + std::to_string(max_length));
+
+ if (max_length == 1) {
+ num_unique &= 0x7f;
+ }
+
+ std::vector<uint32_t> unique_keys_offsets;
+ unique_keys_offsets.resize(num_unique + 1);
+ unique_keys_offsets[0] = 0;
+
+ const int num_bytes = unique_keys_offsets[num_unique];
+ std::vector<uint8_t> unique_keys;
+ unique_keys.resize(num_bytes);
+ std::set<std::string> unique_key_strings;
+ for (int i = 0; i < num_unique; ++i) {
+ for (;;) {
+ int next_length;
+ if (use_varlen_input) {
+ next_length = min_length + random.next() % (max_length - min_length +
1);
+ } else {
+ next_length = max_length;
+ }
+ unique_keys_offsets[i + 1] = unique_keys_offsets[i] + next_length;
+ unique_keys.resize(unique_keys_offsets[i + 1]);
+ uint8_t* next_key = unique_keys.data() + unique_keys_offsets[i];
+
+ for (int iword = 0; iword < next_length /
static_cast<int>(sizeof(uint64_t));
+ ++iword) {
+ reinterpret_cast<uint64_t*>(next_key)[iword] = random.next();
+ }
+ if (next_length % sizeof(uint64_t) > 0) {
+ uint8_t* tail = next_key + next_length - (next_length %
sizeof(uint64_t));
+ for (int ibyte = 0; ibyte < (next_length %
static_cast<int>(sizeof(uint64_t)));
+ ++ibyte) {
+ tail[ibyte] = static_cast<uint8_t>(random.next() & 0xff);
+ }
+ }
+ std::string next_key_string =
+ std::string(reinterpret_cast<const char*>(next_key), next_length);
+ if (unique_key_strings.find(next_key_string) ==
unique_key_strings.end()) {
+ unique_key_strings.insert(next_key_string);
+ break;
+ }
+ }
+ }
+
+ std::vector<int> row_ids;
+ row_ids.resize(num_rows);
+ std::vector<uint8_t> keys;
+ std::vector<uint32_t> keys_offsets;
+ keys_offsets.resize(num_rows + 1);
+ keys_offsets[0] = 0;
+ for (int i = 0; i < num_rows; ++i) {
+ int row_id = random.next() % num_unique;
+ row_ids[i] = row_id;
+ int next_length = unique_keys_offsets[row_id + 1] -
unique_keys_offsets[row_id];
+ keys_offsets[i + 1] = keys_offsets[i] + next_length;
+ }
+ keys.resize(keys_offsets[num_rows]);
+ for (int i = 0; i < num_rows; ++i) {
+ int row_id = row_ids[i];
+ int next_length = keys_offsets[i + 1] - keys_offsets[i];
+ memcpy(keys.data() + keys_offsets[i],
+ unique_keys.data() + unique_keys_offsets[row_id], next_length);
+ }
+
+ constexpr int min_rows_for_timing = 1 << 23;
+ int num_repeats = static_cast<int>(bit_util::CeilDiv(min_rows_for_timing,
num_rows));
+#ifndef NDEBUG
+ num_repeats = 1;
+#endif
+
+ std::vector<uint32_t> hashes_scalar32;
+ std::vector<uint64_t> hashes_scalar64;
+ hashes_scalar32.resize(num_rows);
+ hashes_scalar64.resize(num_rows);
+ std::vector<uint32_t> hashes_simd32;
+ std::vector<uint64_t> hashes_simd64;
+ hashes_simd32.resize(num_rows);
+ hashes_simd64.resize(num_rows);
+
+ int64_t hardware_flags_scalar = 0LL;
+ int64_t hardware_flags_simd = ::arrow::internal::CpuInfo::AVX2;
+
+ constexpr int mini_batch_size = 1024;
+ std::vector<uint32_t> temp_buffer;
+ temp_buffer.resize(mini_batch_size * 4);
+
+ for (bool use_simd : {false, true}) {
+ for (int i = 0; i < num_repeats; ++i) {
+ if (use_32bit_hash) {
+ if (!use_varlen_input) {
+ Hashing32::hash_fixed(use_simd ? hardware_flags_simd :
hardware_flags_scalar,
+ /*combine_hashes=*/false, num_rows, max_length,
+ keys.data(),
+ use_simd ? hashes_simd32.data() :
hashes_scalar32.data(),
+ temp_buffer.data());
+ } else {
+ for (int first_row = 0; first_row < num_rows;) {
+ int batch_size_next = std::min(num_rows - first_row,
mini_batch_size);
+
+ Hashing32::hash_varlen(
+ use_simd ? hardware_flags_simd : hardware_flags_scalar,
+ /*combine_hashes=*/false, batch_size_next,
+ keys_offsets.data() + first_row, keys.data(),
+ (use_simd ? hashes_simd32.data() : hashes_scalar32.data()) +
first_row,
+ temp_buffer.data());
+
+ first_row += batch_size_next;
+ }
+ }
+ } else {
+ if (!use_varlen_input) {
+ Hashing64::hash_fixed(/*combine_hashes=*/false, num_rows, max_length,
+ keys.data(),
+ use_simd ? hashes_simd64.data() :
hashes_scalar64.data());
+ } else {
+ Hashing64::hash_varlen(
+ /*combine_hashes=*/false, num_rows, keys_offsets.data(),
keys.data(),
+ use_simd ? hashes_simd64.data() : hashes_scalar64.data());
+ }
+ }
+ }
+ }
+ if (use_32bit_hash) {
+ for (int i = 0; i < num_rows; ++i) {
+ hashes_scalar64[i] = hashes_scalar32[i];
+ hashes_simd64[i] = hashes_simd32[i];
+ }
+ }
+
+ // Verify that both scalar and AVX2 implementations give the same hashes
+ //
+ for (int i = 0; i < num_rows; ++i) {
+ if (hashes_scalar64[i] != hashes_simd64[i]) {
+ ARROW_DCHECK(false);
+ }
+ }
+
+ // Verify that the same key appearing multiple times generates the same hash
+ // each time. Measure the number of unique hashes and compare to the number
+ // of unique keys.
+ //
+ std::map<int, uint64_t> unique_key_to_hash;
+ std::set<uint64_t> unique_hashes;
+ for (int i = 0; i < num_rows; ++i) {
+ std::map<int, uint64_t>::iterator iter =
unique_key_to_hash.find(row_ids[i]);
+ if (iter == unique_key_to_hash.end()) {
+ unique_key_to_hash.insert(std::make_pair(row_ids[i],
hashes_scalar64[i]));
+ } else {
+ ARROW_DCHECK(iter->second == hashes_scalar64[i]);
+ }
+ if (unique_hashes.find(hashes_scalar64[i]) == unique_hashes.end()) {
+ unique_hashes.insert(hashes_scalar64[i]);
+ }
+ }
+ float percent_hash_collisions = 100.0f *
+ static_cast<float>(num_unique -
unique_hashes.size()) /
+ static_cast<float>(num_unique);
+ SCOPED_TRACE("percent_hash_collisions " +
std::to_string(percent_hash_collisions));
+ ARROW_DCHECK(percent_hash_collisions < 5.0f);
+}
+
+TEST(VectorHash, Basic) {
+ Random64Bit random(/*seed=*/0);
+
+ int numtest = 100;
+
+ constexpr int min_length = 1;
+ constexpr int max_length = 50;
+
+ for (bool use_32bit_hash : {true, false}) {
+ for (bool use_varlen_input : {false, true}) {
+ for (int itest = 0; itest < numtest; ++itest) {
+ int length = static_cast<int>(std::max(
+ static_cast<uint64_t>(use_varlen_input ? 2 : 1),
+ static_cast<uint64_t>(min_length +
+ random.next() % (max_length - min_length +
1))));
Review comment:
Given that we are already choose keys of random lengths I don't know
that there is much need to also randomize the max length. We could just always
use 50.
##########
File path: cpp/src/arrow/compute/exec/vector_hash_test.cc
##########
@@ -0,0 +1,234 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#include <gmock/gmock-matchers.h>
+
+#include <chrono>
+#include <map>
+#include <set>
+#include "arrow/compute/exec/key_hash.h"
+#include "arrow/compute/exec/test_util.h"
+#include "arrow/compute/exec/util.h"
+#include "arrow/util/cpu_info.h"
+
+namespace arrow {
+namespace compute {
+
+void TestVectorHashImp(Random64Bit& random, bool use_32bit_hash, bool
use_varlen_input,
+ int min_length, int max_length) {
+ ARROW_DCHECK(use_varlen_input || min_length == max_length);
+
+ constexpr int min_num_unique = 100;
+ constexpr int max_num_unique = 1000;
+ constexpr int min_num_rows = 4000;
+ constexpr int max_num_rows = 64000;
+ int num_unique =
+ min_num_unique + (random.next() % (max_num_unique - min_num_unique + 1));
+ int num_rows = min_num_rows + (random.next() % (max_num_rows - min_num_rows
+ 1));
+
+ SCOPED_TRACE("num_bits = " + std::to_string(use_32bit_hash ? 32 : 64) +
+ " varlen = " + std::string(use_varlen_input ? "yes" : "no") +
+ " num_unique " + std::to_string(num_unique) + " num_rows " +
+ std::to_string(num_rows) + " min_length " +
std::to_string(min_length) +
+ " max_length " + std::to_string(max_length));
+
+ if (max_length == 1) {
+ num_unique &= 0x7f;
+ }
+
+ std::vector<uint32_t> unique_keys_offsets;
+ unique_keys_offsets.resize(num_unique + 1);
+ unique_keys_offsets[0] = 0;
+
+ const int num_bytes = unique_keys_offsets[num_unique];
+ std::vector<uint8_t> unique_keys;
+ unique_keys.resize(num_bytes);
+ std::set<std::string> unique_key_strings;
+ for (int i = 0; i < num_unique; ++i) {
+ for (;;) {
+ int next_length;
+ if (use_varlen_input) {
+ next_length = min_length + random.next() % (max_length - min_length +
1);
+ } else {
+ next_length = max_length;
+ }
+ unique_keys_offsets[i + 1] = unique_keys_offsets[i] + next_length;
+ unique_keys.resize(unique_keys_offsets[i + 1]);
+ uint8_t* next_key = unique_keys.data() + unique_keys_offsets[i];
+
+ for (int iword = 0; iword < next_length /
static_cast<int>(sizeof(uint64_t));
+ ++iword) {
+ reinterpret_cast<uint64_t*>(next_key)[iword] = random.next();
+ }
+ if (next_length % sizeof(uint64_t) > 0) {
+ uint8_t* tail = next_key + next_length - (next_length %
sizeof(uint64_t));
+ for (int ibyte = 0; ibyte < (next_length %
static_cast<int>(sizeof(uint64_t)));
+ ++ibyte) {
+ tail[ibyte] = static_cast<uint8_t>(random.next() & 0xff);
+ }
+ }
+ std::string next_key_string =
+ std::string(reinterpret_cast<const char*>(next_key), next_length);
+ if (unique_key_strings.find(next_key_string) ==
unique_key_strings.end()) {
+ unique_key_strings.insert(next_key_string);
+ break;
+ }
+ }
+ }
+
+ std::vector<int> row_ids;
+ row_ids.resize(num_rows);
+ std::vector<uint8_t> keys;
+ std::vector<uint32_t> keys_offsets;
+ keys_offsets.resize(num_rows + 1);
+ keys_offsets[0] = 0;
+ for (int i = 0; i < num_rows; ++i) {
+ int row_id = random.next() % num_unique;
+ row_ids[i] = row_id;
+ int next_length = unique_keys_offsets[row_id + 1] -
unique_keys_offsets[row_id];
+ keys_offsets[i + 1] = keys_offsets[i] + next_length;
+ }
+ keys.resize(keys_offsets[num_rows]);
+ for (int i = 0; i < num_rows; ++i) {
+ int row_id = row_ids[i];
+ int next_length = keys_offsets[i + 1] - keys_offsets[i];
+ memcpy(keys.data() + keys_offsets[i],
+ unique_keys.data() + unique_keys_offsets[row_id], next_length);
+ }
+
+ constexpr int min_rows_for_timing = 1 << 23;
+ int num_repeats = static_cast<int>(bit_util::CeilDiv(min_rows_for_timing,
num_rows));
+#ifndef NDEBUG
+ num_repeats = 1;
+#endif
+
+ std::vector<uint32_t> hashes_scalar32;
+ std::vector<uint64_t> hashes_scalar64;
+ hashes_scalar32.resize(num_rows);
+ hashes_scalar64.resize(num_rows);
+ std::vector<uint32_t> hashes_simd32;
+ std::vector<uint64_t> hashes_simd64;
+ hashes_simd32.resize(num_rows);
+ hashes_simd64.resize(num_rows);
+
+ int64_t hardware_flags_scalar = 0LL;
+ int64_t hardware_flags_simd = ::arrow::internal::CpuInfo::AVX2;
+
+ constexpr int mini_batch_size = 1024;
+ std::vector<uint32_t> temp_buffer;
+ temp_buffer.resize(mini_batch_size * 4);
+
+ for (bool use_simd : {false, true}) {
+ for (int i = 0; i < num_repeats; ++i) {
+ if (use_32bit_hash) {
+ if (!use_varlen_input) {
+ Hashing32::hash_fixed(use_simd ? hardware_flags_simd :
hardware_flags_scalar,
+ /*combine_hashes=*/false, num_rows, max_length,
+ keys.data(),
+ use_simd ? hashes_simd32.data() :
hashes_scalar32.data(),
+ temp_buffer.data());
+ } else {
+ for (int first_row = 0; first_row < num_rows;) {
+ int batch_size_next = std::min(num_rows - first_row,
mini_batch_size);
+
+ Hashing32::hash_varlen(
+ use_simd ? hardware_flags_simd : hardware_flags_scalar,
+ /*combine_hashes=*/false, batch_size_next,
+ keys_offsets.data() + first_row, keys.data(),
+ (use_simd ? hashes_simd32.data() : hashes_scalar32.data()) +
first_row,
+ temp_buffer.data());
+
+ first_row += batch_size_next;
+ }
+ }
+ } else {
+ if (!use_varlen_input) {
+ Hashing64::hash_fixed(/*combine_hashes=*/false, num_rows, max_length,
+ keys.data(),
+ use_simd ? hashes_simd64.data() :
hashes_scalar64.data());
+ } else {
+ Hashing64::hash_varlen(
+ /*combine_hashes=*/false, num_rows, keys_offsets.data(),
keys.data(),
+ use_simd ? hashes_simd64.data() : hashes_scalar64.data());
+ }
+ }
+ }
+ }
+ if (use_32bit_hash) {
+ for (int i = 0; i < num_rows; ++i) {
+ hashes_scalar64[i] = hashes_scalar32[i];
+ hashes_simd64[i] = hashes_simd32[i];
+ }
+ }
+
+ // Verify that both scalar and AVX2 implementations give the same hashes
+ //
+ for (int i = 0; i < num_rows; ++i) {
+ if (hashes_scalar64[i] != hashes_simd64[i]) {
+ ARROW_DCHECK(false);
+ }
+ }
+
+ // Verify that the same key appearing multiple times generates the same hash
+ // each time. Measure the number of unique hashes and compare to the number
+ // of unique keys.
+ //
+ std::map<int, uint64_t> unique_key_to_hash;
+ std::set<uint64_t> unique_hashes;
+ for (int i = 0; i < num_rows; ++i) {
+ std::map<int, uint64_t>::iterator iter =
unique_key_to_hash.find(row_ids[i]);
+ if (iter == unique_key_to_hash.end()) {
+ unique_key_to_hash.insert(std::make_pair(row_ids[i],
hashes_scalar64[i]));
+ } else {
+ ARROW_DCHECK(iter->second == hashes_scalar64[i]);
+ }
+ if (unique_hashes.find(hashes_scalar64[i]) == unique_hashes.end()) {
+ unique_hashes.insert(hashes_scalar64[i]);
+ }
+ }
+ float percent_hash_collisions = 100.0f *
+ static_cast<float>(num_unique -
unique_hashes.size()) /
+ static_cast<float>(num_unique);
+ SCOPED_TRACE("percent_hash_collisions " +
std::to_string(percent_hash_collisions));
+ ARROW_DCHECK(percent_hash_collisions < 5.0f);
+}
+
+TEST(VectorHash, Basic) {
+ Random64Bit random(/*seed=*/0);
+
+ int numtest = 100;
Review comment:
```suggestion
int numtest = 10;
```
Since this is just going to be for detecting regression (and not
benchmarking) we should drop this down so this test is in line with our other
unit tests.
##########
File path: cpp/src/arrow/compute/exec/vector_hash_test.cc
##########
@@ -0,0 +1,234 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#include <gmock/gmock-matchers.h>
+
+#include <chrono>
+#include <map>
+#include <set>
+#include "arrow/compute/exec/key_hash.h"
+#include "arrow/compute/exec/test_util.h"
+#include "arrow/compute/exec/util.h"
+#include "arrow/util/cpu_info.h"
+
+namespace arrow {
+namespace compute {
+
+void TestVectorHashImp(Random64Bit& random, bool use_32bit_hash, bool
use_varlen_input,
+ int min_length, int max_length) {
+ ARROW_DCHECK(use_varlen_input || min_length == max_length);
+
+ constexpr int min_num_unique = 100;
+ constexpr int max_num_unique = 1000;
+ constexpr int min_num_rows = 4000;
+ constexpr int max_num_rows = 64000;
+ int num_unique =
+ min_num_unique + (random.next() % (max_num_unique - min_num_unique + 1));
+ int num_rows = min_num_rows + (random.next() % (max_num_rows - min_num_rows
+ 1));
+
+ SCOPED_TRACE("num_bits = " + std::to_string(use_32bit_hash ? 32 : 64) +
+ " varlen = " + std::string(use_varlen_input ? "yes" : "no") +
+ " num_unique " + std::to_string(num_unique) + " num_rows " +
+ std::to_string(num_rows) + " min_length " +
std::to_string(min_length) +
+ " max_length " + std::to_string(max_length));
+
+ if (max_length == 1) {
+ num_unique &= 0x7f;
+ }
+
+ std::vector<uint32_t> unique_keys_offsets;
+ unique_keys_offsets.resize(num_unique + 1);
+ unique_keys_offsets[0] = 0;
+
+ const int num_bytes = unique_keys_offsets[num_unique];
+ std::vector<uint8_t> unique_keys;
+ unique_keys.resize(num_bytes);
+ std::set<std::string> unique_key_strings;
Review comment:
```suggestion
std::vector<uint8_t> unique_keys;
std::set<std::string> unique_key_strings;
```
`num_bytes` will always be 0.
##########
File path: cpp/src/arrow/compute/exec/vector_hash_test.cc
##########
@@ -0,0 +1,234 @@
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements. See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership. The ASF licenses this file
+// to you under the Apache License, Version 2.0 (the
+// "License"); you may not use this file except in compliance
+// with the License. You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing,
+// software distributed under the License is distributed on an
+// "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+// KIND, either express or implied. See the License for the
+// specific language governing permissions and limitations
+// under the License.
+
+#include <gmock/gmock-matchers.h>
+
+#include <chrono>
+#include <map>
+#include <set>
+#include "arrow/compute/exec/key_hash.h"
+#include "arrow/compute/exec/test_util.h"
+#include "arrow/compute/exec/util.h"
+#include "arrow/util/cpu_info.h"
+
+namespace arrow {
+namespace compute {
+
+void TestVectorHashImp(Random64Bit& random, bool use_32bit_hash, bool
use_varlen_input,
Review comment:
This test should be using `HashMultiColumn` as that is the public API
and it isn't covered elsewhere and there is some non-trivial null handling
logic there (we should also be testing with nulls).
In addition, there is no coverage of hash_bit
Finally, there is no coverage of multiple column hashes or hash combination
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