GMP compared to JAVA

[Jan Doornaert]

 Hello,

I'd first of all replace

mpz_init_set_ui (exp,  1);

by

mpz_set_ui (exp,  1);

and redo the timing test (you already mpz_init-ed exp - and you will only mpz_clear it once)

CU, JDO

  ----- Original Message -----
  From: "Nustenil Segundo"
  To: gmp-discuss at swox.com
  Subject: GMP compared to JAVA
  Date: Thu, 20 Dec 2007 20:37:54 -0300


  Hi,

  I did a aplication with GMP and other same in JAVA.
  This aplication calculates the value of the operation a^b mod m, for
  a, b and m randomical numbers of n bits, n in interval [5, 25000).

  The code in C (using GMP):

  #include
  #include
  #include
  #include


  int main()
  {
  //Declaração de variáveis
  mpz_t op1, op2, mod, x, aux, exp;
  gmp_randstate_t state;
  unsigned long int n = 4, seed, i, j;
  clock_t ini, fim, temp;
  FILE *p;

  srand(time(NULL));

  //inicialização das variáveis do tipo GMP
  mpz_init(op2);
  mpz_init(x);
  mpz_init(op1);
  mpz_init(mod);
  mpz_init(aux);
  mpz_init(exp);
  gmp_randinit_default(state);
  //abre o arquivo "arquivo.txt" para escrita
  p = fopen("arquivomassa.txt", "w");

  //laço para medir os bits e o tempo
  for(i=5 ; i<25000; i+=10){

  mpz_init_set_ui (exp, 1);
  seed= rand();
  gmp_randseed_ui (state,seed);
  //laço para o cálculo de 2^exp
  for(j=1; j<=i; j++){
  mpz_mul_ui(exp, exp, 2);
  }

  mpz_urandomb(aux, state, i); //aux Ã(c) um número
  aleatório de 0 a 2^i-1
  mpz_add (op1, aux, exp); //op1 Ã(c) um número de
  (i+1) bits

  mpz_urandomb(aux, state, i); //aux Ã(c) um número
  aleatório de 0 a 2^i-1
  mpz_add (op2, aux, exp); //op2 Ã(c) um número de
  (i+1) bits

  mpz_urandomb(aux, state, i); //aux Ã(c) um número
  aleatório de 0 a 2^i-1
  mpz_add (mod, aux, exp); //mod Ã(c) um número de
  (i+1) bits

  //calcula o tempo de [((op1)^(p2)) mod (mod)] e armazena em temp
  ini = clock();
  mpz_powm (x, op1, op2, mod);
  fim = clock();
  temp = fim - ini;

  printf("%lu\n", 1000*(unsigned long) temp/CLOCKS_PER_SEC);
  //armazena em arquivo.txt a quantidade de bits e o tempo
  da operação
  fprintf(p, "%lu\t%lu\n", i+1, 1000*(unsigned
  long)temp/CLOCKS_PER_SEC);
  }

  gmp_randclear (state);
  mpz_clear (op1);
  mpz_clear (op2);
  mpz_clear (mod);
  mpz_clear (x);
  mpz_clear (aux);
  mpz_clear (exp);


  return 0;
  }

  The code in JAVA:

  import java.io.IOException ;
  import java.io.RandomAccessFile;
  import java.math.BigDecimal;
  import java.math.BigInteger;
  import java.util.Calendar;



  public class Big {

  /**
  * @param args
  * @throws IOException
  */
  public static void main(String[] args) throws IOException {
  // String saida = "";
  BigDecimal aux = new BigDecimal("16");
  // BigDecimal condicaoParada = new BigDecimal("10").pow(1000);
  long cont = 5;
  String fimDeLinha = System.getProperty(" line.separator");
  RandomAccessFile arquivo = new RandomAccessFile("tabela.txt","rw");
  while(cont < 25000){
  BigDecimal aleatorio = (new BigDecimal(
  Math.random()).multiply(aux)).add(aux);
  BigInteger p = new
  BigInteger(aleatorio.toString().substring(0, aleatorio.toString
  ().indexOf(".")));
  aleatorio = (new
  BigDecimal(Math.random()).multiply(aux)).add(aux);
  BigInteger q = new
  BigInteger(aleatorio.toString().substring(0,
  aleatorio.toString().indexOf(".")));
  aleatorio = (new
  BigDecimal(Math.random()).multiply(aux)).add(aux);
  BigInteger m = new BigInteger(
  aleatorio.toString().substring(0,
  aleatorio.toString().indexOf(".")));
  // saida += ;
  String saida = cont+" \t"+calculaTempo(p, q, m)+fimDeLinha;
  arquivo.seek (arquivo.length());
  arquivo.write(saida.getBytes());
  System.out.print(saida);
  cont+=10;
  aux = aux.multiply(new BigDecimal("1024"));
  }
  // System.out.println(saida);
  }

  private static long calculaTempo(BigInteger p, BigInteger q,
  BigInteger m) {
  long tempoInicial = Calendar.getInstance().getTimeInMillis();
  BigInteger calculo = p.modPow(q, m);
  // BigInteger calculo = powBigInteger(p, q).mod(m);
  // q.
  long tempoFinal = Calendar.getInstance().getTimeInMillis();
  // System.out.println("------ "+calculo);
  return tempoFinal - tempoInicial;
  }


  }


  For the result in C with n = 10005 bits the time was 2800 ms (a
  example).

  For the result in JAVA with n = 10005 bits the time was 10 ms (a
  example).


  Why this difference?

  Thanks,

  Nustenil Segundo de Moraes Lima Marinus
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