Pros of SMHasher

• Comprehensive test suite for hash functions
• Supports a wide range of hash algorithms
• Provides detailed performance and quality metrics

Cons of SMHasher

• More complex to use and understand
• Larger codebase with multiple dependencies
• Slower execution due to extensive testing

Code Comparison

SMHasher (test execution):

#include "SMHasher.h"

int main(int argc, char ** argv) {
    TestHashList(argc, argv);
    return 0;
}

wyhash (hash function implementation):

static inline uint64_t wyhash(const void *key, uint64_t len, uint64_t seed) {
    const uint8_t *p = (const uint8_t *)key;
    uint64_t a, b;
    if (len <= 16) {
        // ... (hash calculation for short keys)
    }
    // ... (hash calculation for longer keys)
}

SMHasher focuses on testing and benchmarking various hash functions, while wyhash provides a simple, fast hash function implementation. SMHasher is more suitable for researchers and developers evaluating hash function quality, while wyhash is designed for practical use in applications requiring a quick and efficient hash function.

Pros of xxHash

• Widely adopted and battle-tested in various applications
• Excellent performance on x86 and ARM architectures
• Extensive documentation and API support

Cons of xxHash

• Slightly larger code footprint compared to wyhash
• May have slower performance on some non-x86/ARM platforms

Code Comparison

xxHash:

XXH64_hash_t XXH64(const void* input, size_t length, XXH64_hash_t seed)
{
    // Complex implementation with multiple branches and loops
}

wyhash:

uint64_t wyhash(const void* key, uint64_t len, uint64_t seed)
{
    // Simpler implementation with fewer branches
}

Key Differences

• xxHash offers multiple variants (32-bit, 64-bit, 128-bit) while wyhash focuses on 64-bit
• wyhash claims to be faster and simpler, especially on non-x86 platforms
• xxHash has a more extensive ecosystem and third-party language bindings

Use Cases

• xxHash: Ideal for applications requiring a well-established, widely-supported hash function
• wyhash: Suitable for projects prioritizing simplicity and performance across various platforms

Community and Support

• xxHash: Larger community, more frequent updates, and extensive documentation
• wyhash: Smaller community but active development and responsive maintainer

Pros of robin-hood-hashing

• Implements Robin Hood hashing, which can provide better performance in certain scenarios
• More comprehensive library with additional features and data structures
• Well-documented with extensive benchmarks and examples

Cons of robin-hood-hashing

• Larger codebase and more complex implementation
• May have higher memory usage due to additional metadata
• Potentially slower for simple use cases or small datasets

Code Comparison

wyhash:

uint64_t wyhash(const void* key, uint64_t len, uint64_t seed) {
  const uint8_t *p = (const uint8_t*)key;
  uint64_t a, b;
  if (len <= 16) {
    // ... (simplified for brevity)
  }
}

robin-hood-hashing:

template <typename Key, typename T, typename Hash = hash<Key>,
          typename KeyEqual = equal_to<Key>>
class unordered_map {
 public:
  using key_type = Key;
  using mapped_type = T;
  // ... (additional type definitions and methods)
};

The wyhash repository focuses on a single, fast hashing function, while robin-hood-hashing provides a more comprehensive hash table implementation with additional features. wyhash is simpler and may be faster for basic hashing needs, while robin-hood-hashing offers more advanced functionality at the cost of increased complexity.