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//******************************************************************************
//
// File: PrimeCountFunctionSeq.java
// Package: edu.rit.hyb.prime
// Unit: Class edu.rit.hyb.prime.PrimeCountFunctionSeq
//
// This Java source file is copyright (C) 2008 by Alan Kaminsky. All rights
// reserved. For further information, contact the author, Alan Kaminsky, at
// ark@cs.rit.edu.
//
// This Java source file is part of the Parallel Java Library ("PJ"). PJ is free
// software; you can redistribute it and/or modify it under the terms of the GNU
// General Public License as published by the Free Software Foundation; either
// version 3 of the License, or (at your option) any later version.
//
// PJ is distributed in the hope that it will be useful, but WITHOUT ANY
// WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
// A PARTICULAR PURPOSE. See the GNU General Public License for more details.
//
// Linking this library statically or dynamically with other modules is making a
// combined work based on this library. Thus, the terms and conditions of the
// GNU General Public License cover the whole combination.
//
// As a special exception, the copyright holders of this library give you
// permission to link this library with independent modules to produce an
// executable, regardless of the license terms of these independent modules, and
// to copy and distribute the resulting executable under terms of your choice,
// provided that you also meet, for each linked independent module, the terms
// and conditions of the license of that module. An independent module is a
// module which is not derived from or based on this library. If you modify this
// library, you may extend this exception to your version of the library, but
// you are not obligated to do so. If you do not wish to do so, delete this
// exception statement from your version.
//
// A copy of the GNU General Public License is provided in the file gpl.txt. You
// may also obtain a copy of the GNU General Public License on the World Wide
// Web at http://www.gnu.org/licenses/gpl.html.
//
//******************************************************************************
package edu.rit.hyb.prime;
import edu.rit.pj.Comm;
import java.io.File;
/**
* Class PrimeCountFunctionSeq is a sequential program that calculates the prime
* counting function π(<I>x</I>). π(<I>x</I>) is the number of primes less
* than or equal to <I>x</I>. The program uses a list of 32-bit primes stored in
* a file. The prime file must be generated by the {@linkplain Prime32File}
* program. To find the primes, the program calculates a series of sieves. Each
* sieve consists of one million numbers.
* <P>
* Usage: java edu.rit.hyb.prime.PrimeCountFunctionSeq <I>x</I>
* <I>primefile</I>
* <BR><I>x</I> = Argument of prime counting function, 0 <= <I>x</I> <=
* 2<SUP>63</SUP>-1
* <BR><I>primefile</I> = Prime file name
* <P>
* The computation is performed sequentially in a single processor. The program
* measures the total running time. This establishes a benchmark for measuring
* the running time on a parallel processor.
*
* @author Alan Kaminsky
* @version 05-Jun-2008
*/
public class PrimeCountFunctionSeq
{
// Prevent construction.
private PrimeCountFunctionSeq()
{
}
// Shared global variables.
// Sieve in one-million-number chunks.
static final int CHUNK = 1000000;
// Command line arguments.
static long x;
static File primefile;
// Main program.
/**
* Main program.
*/
public static void main
(String[] args)
throws Exception
{
// Start timing.
long t1 = System.currentTimeMillis();
// World communicator.
Comm.init (args);
// Parse command line arguments.
if (args.length != 2) usage();
x = Long.parseLong (args[0]);
if (x < 0) usage();
primefile = new File (args[1]);
// Set up sieve.
Sieve sieve = new Sieve (0, CHUNK);
// Set up list of 32-bit primes.
Prime32List primeList = new Prime32List (primefile);
// For counting primes. Initially 1 to count prime number 2.
long primeCount = 1;
// Do all chunks.
for (long lb = 0; lb >= 0 && lb <= x; lb += CHUNK)
{
// Get an iterator for the odd primes.
LongIterator iter = primeList.iterator();
// Sieve the chunk.
sieve.lb (lb);
sieve.initialize();
sieve.sieveOut (iter);
// Count primes <= x left in the chunk.
iter = sieve.iterator();
long p;
while ((p = iter.next()) != 0 && p <= x) ++ primeCount;
}
// Stop timing.
long t2 = System.currentTimeMillis();
// Print the answer.
System.out.println ("pi("+x+") = "+primeCount);
System.out.println ((t2-t1)+" msec");
}
// Hidden operations.
/**
* Print a usage message and exit.
*/
private static void usage()
{
System.err.println ("Usage: java edu.rit.hyb.prime.PrimeCountFunctionSeq <x> <primefile>");
System.err.println ("<x> = Argument of prime counting function, 0 <= <x> <= 2^63-1");
System.err.println ("<primefile> = Prime file name");
System.exit (1);
}
}
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