| // 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 <stdlib.h> |
| #include <stdio.h> |
| #include <iostream> |
| #include <vector> |
| |
| #include "util/hash-util.h" |
| #include "util/cpu-info.h" |
| |
| #include "common/names.h" |
| |
| using namespace impala; |
| |
| // Test collision problem with multiple mod steps (IMPALA-219) |
| int main(int argc, char **argv) { |
| google::InitGoogleLogging(argv[0]); |
| CpuInfo::Init(); |
| |
| int num_buckets1 = 16; |
| int num_buckets2 = 1024; |
| int num_values = num_buckets1 * num_buckets2; |
| |
| int num_collisions1 = 0; |
| int num_collisions2 = 0; |
| int num_empty2 = num_buckets2; |
| vector<bool> buckets1; |
| vector<bool> buckets2; |
| buckets1.resize(num_buckets1); |
| buckets2.resize(num_buckets2); |
| |
| // First test using the same hash fn both times |
| for (int i = 0; i < num_values; ++i) { |
| uint32_t hash1 = HashUtil::Hash(&i, sizeof(int), 0) >> 8; |
| uint32_t hash2 = HashUtil::Hash(&i, sizeof(int), 1) >> 8; |
| uint32_t bucket1_idx = hash1 % num_buckets1; |
| if (buckets1[bucket1_idx]) ++num_collisions1; |
| buckets1[bucket1_idx] = true; |
| |
| LOG(ERROR) << i << ":" << hash1 << ":" << hash2; |
| // If they matched bucket 0, put it into buckets2 |
| if (bucket1_idx == 0) { |
| uint32_t bucket2_idx = hash2 % num_buckets2; |
| if (buckets2[bucket2_idx]) { |
| ++num_collisions2; |
| } else { |
| buckets2[bucket2_idx] = true; |
| --num_empty2; |
| } |
| } |
| } |
| |
| LOG(ERROR) << "Same hash:" << endl |
| << " Bucket 1 Collisions: " << num_collisions1 << endl |
| << " Expected 1 Collisions: " << num_values - num_buckets1 << endl |
| << " Bucket 2 Collisions: " << num_collisions2 << endl |
| << " Bucket 2 Empties: " << num_empty2 << endl |
| << " Bucket 2 Total Values: " << num_values / num_buckets1; |
| |
| return 0; |
| } |