Python hashlib is twice as fast as Java MessageDigest: see the related post here: http://cppsfn.co/hashlib-vs-messagedigest

java_multiple_hashing.java

public static double comparison(int desiredSize, int bufferSize){
  int size = desiredSize / bufferSize * bufferSize;
  byte data[] = new byte[size];
  new Random().nextBytes(data);
  long startTime = 0;
  long endTime = 0;
  int nRounds = 10;
  double elapsed = 0;
  for(int round = 0; round < nRounds; round++){
    MessageDigest sha = MessageDigest.getInstance("SHA-256");
    startTime = System.nanoTime();
    for(int i = 0; i < size; i += bufferSize)
      sha.update(data, i, bufferSize);
    sha.digest();
    endTime = System.nanoTime();
    elapsed += ((endTime - startTime) / 1000000000.0);
  }
  return elapsed / nRounds;
}

java_single_hashing.java

public static void comparisonAlone(int size){
  byte data[] = new byte[size];
  new Random().nextBytes(data);
  int nRounds = 10;
  double total = 0;
  for(int round = 0; round < nRounds; round++) {
    MessageDigest sha = MessageDigest.getInstance("SHA-256");
    long start = System.nanoTime();
    sha.digest(data);
    long end = System.nanoTime();
    total += ((end - start) / 1000000000.);
  }
  System.out.println(total / nRounds);
}

python_multiple_hashing.py

def comparison(desired_size, buffer_size):
    size = (desired_size // buffer_size) * buffer_size
    data = np.random.bytes(size)
    n_rounds = 10
    elapsed = 0
    for round in range(n_rounds):
        sha = hashlib.sha256()
        start = time.time()
        for i in range(0, size, buffer_size):
            sha.update(data[i:i+buffer_size])
        sha.digest()
        end = time.time()
        elapsed += (start - end)
    return elapsed / n_rounds

python_single_hashing.py

def comparison_alone(size):
    data = np.random.bytes(size)
    n_rounds = 10
    total = 0
    for _ in range(n_rounds):
        sha = hashlib.sha256()
        start = time.time()
        sha.update(data)
        sha.digest()
        end = time.time()
        total += (end - start)
    print(total / n_rounds)