Pla$orm independence and languages. CSCI 136: Fundamentals of Computer Science II Keith Vertanen

Transcription

1 Pla$orm independence and languages CSCI 136: Fundamentals of Computer Science II Keith Vertanen

2 Language types: Compiled e.g. C++ Overview Intermediate / bytecode e.g. Java,.NET Interpreted e.g. PHP, JavaScript Performance comparison 2

3 GeneraIng primes Problem: Compute all the primes up to N Prime # is only divisible by 1 and itself ANempt 1: Brute force Loop over all the numbers [2, N] For each #, check if anything evenly divides it... for (int i = 2; i <= N; i++) int j = 2; while ((j < i) && (i % j!= 0)) j++; if (j == i) System.out.printf("%d ", i);... PrimesNested.java

4 GeneraIng primes ANempt 2: Sieve of Eratosthenes

5 public class Primes public static void main(string [] args) final int N = Integer.parseInt(args[0]); boolean [] a = new boolean[n + 1]; for (int i = 0; i <= N; i++) a[i] = true; int top = (int) Math.sqrt((double) N); for (int i = 2; i <= top; i++) int j = 2 * i; while (j <= N) a[j] = false; j += i; for (int i = 2; i <= N; i++) if (a[i]) System.out.printf("%d ", i); System.out.printf("\n"); Primes.java 5

6 public class Primes public static void main(string [] args) final int N = Integer.parseInt(args[0]); boolean [] a = new boolean[n + 1]; for (int i = 0; i <= N; i++) a[i] = true; int top = (int) Math.sqrt((double) N); for (int i = 2; i <= top; i++) int j = 2 * i; while (j <= N) a[j] = false; j += i; for (int i = 2; i <= N; i++) if (a[i]) System.out.printf("%d ", i); System.out.printf("\n"); Primes.java #include <stdio.h> #include <stdlib.h> #include <math.h> int main(int argc, char** argv) const int N = atoi(argv[1]); bool* a = new bool[n + 1]; for (int i = 0; i <= N; i++) a[i] = true; int top = (int) sqrt((double) N); for (int i = 2; i <= top; i++) int j = 2 * i; while (j <= n) a[j] = false; j += i; for (int i = 2; i <= N; i++) if (a[i]) printf("%d ", i); printf("\n"); delete [] a; return 0; Primes.cpp Maybe you've never seen C before, but you can read it! 6

7 NaIve compilaion C/C++ Write the code Press compile bunon Wait Fix compile errors Press compile bunon hnp://xkcd.com/303/ Compiled naive code loaded directly on CPU Code is specific to targeted architecture: Compile for Windows x86 Compile for Mac x86 7

8 Source code: Plain text file created in a high- level programming language #include <stdio.h> #include <stdlib.h> #include <math.h> int main(int argc, char** argv) int n = atoi(argv[1]);... Primes.cpp Compile with GNU C++ compiler: c:\source\c\primes>g++ -O3 Primes.cpp -o Primes Machine language: Actual binary run by a paricular processor, not human readable/writeable Primes.exe c:\source\c\primes>primes Specific to the architecture targeted by compiler (e.g. x86) 8

9 Source code: Plain text file created in a high- level programming language Compile with Visual Studio: #include <stdio.h> #include <stdlib.h> #include <math.h> int main(int argc, char** argv) int n = atoi(argv[1]);... Primes.cpp Primes.exe Somewhat different binary than GNU's output, but should work on same architecture. 9

10 Different targets in Visual Studio 10

11 Assembly language C Keil IDE Keil IDE Primes.asm Hex file Primes.c MRT: Loads machine code into code memory of 8051 board 8051 educafonal board 11

12 8051 assembly: IniIalizing an array ; Parameters to our ArrayInit subroutine ArrayNum EQU 30h ; Where our array starts ArrayMemStart EQU 31h ; 1st memory location in the array ArrayInitVal EQU 32h ; What value to load into array Start: MOV ArrayNum, #10 MOV ArrayMemStart, #40h MOV ArrayInitVal, #0ABh CALL ArrayInit JMP Start ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;; ; Init the memory in an array to a value, uses R0 and R1 ArrayInit: MOV R0, ArrayNum MOV R1, ArrayMemStart ArrayInitLoop: ArrayInitVal INC R1 DJNZ R0, ArrayInitLoop RET 12

13 Source code: Plain text file created in some editor (notepad, vi, TextEdit, Eclipse, DrJava, ) public class Primes public static void main(string [] args) int n = Integer.parseInt(args[0]);... Primes.java % javac Primes.java Java bytecode: Intermediate language that any device running Java can understand LineNumberTable main ([Ljava/lang/String;)V StackMapTable # SourceFile Primes.java * +, %d java/lang/object Primes.class c:\source\c\primes>java Primes This guy will run on anything with a Java Virtual Machine (JVM) 13

14 Source code (text) PlaTorm independent bytecode (binary) PlaTorm dependent virtual machine (binary executable) Target hardware 14

15 Other intermediate pla$orms Microsok.NET framework Write source in a variety of languages: C#, VB.NET, J#, F# Compile to Common Intermediate Language (CIL) Executed by Common Language RunIme (CLR) 15

16 16

17 using System; namespace Primes class Primes static void Main(string[] args) int n = Int32.Parse(args[0]); bool[] a = new bool[n + 1]; for (int i = 0; i <= n; i++) a[i] = true; int top = (int) Math.Sqrt((double) n); for (int i = 2; i <= top; i++) int j = 2 * i; while (j <= n) a[j] = false; j += i; public class Primes public static void main(string [] args) final int N = Integer.parseInt(args[0]); boolean [] a = new boolean[n + 1]; for (int i = 0; i <= N; i++) a[i] = true; int top = (int) Math.sqrt((double) N); for (int i = 2; i <= top; i++) int j = 2 * i; while (j <= N) a[j] = false; j += i; for (int i = 2; i <= n; i++) if (a[i]) System.Console.Write(i + " "); System.Console.WriteLine(); for (int i = 2; i <= N; i++) if (a[i]) System.out.printf("%d ", i); System.out.printf("\n"); Primes.cs Primes.java 17

18 Bytecode advantages Pla$orm independence Write once, run anywhere At anywhere someone has wrinen a virtual machine Possibly faster than pre- compiling??? Just In Time (JIT) compiler Security Can opimize bytecode to CPU it is running on Difficult to do this if you compile in advance You would have to deploy a version for every CPU variant Virtual Machine (VM) can verify code is behaving 18

19 Interpreted languages No compilaion step before running Each line compiled as encountered Originally some programming languages e.g. Smalltalk, BASIC Other scriping languages e.g. DOS batch files, bash scripts, PHP, JavaScript Now most uilize Just In Time (JIT) compilers Cache previously compiled lines of code Many languages thought of as "interpreted" now use bytecode approach e.g. Python, Perl, Ruby 19

20 <?php $n = $_GET["N"]; $a = array(); for ($i = 0; $i <= $n; $i++) $a[$i] = true; public class Primes public static void main(string [] args) final int N = Integer.parseInt(args[0]); boolean [] a = new boolean[n + 1]; for (int i = 0; i <= N; i++) a[i] = true; $top = intval(sqrt($n)); for ($i = 2; $i <= $top; $i++) $j = 2 * $i; while ($j <= $n) $a[$j] = false; $j += $i; for ($i = 2; $i <= $n; $i++) if ($a[$i]) echo "$i "; echo "<br />";?> Primes.php int top = (int) Math.sqrt((double) N); for (int i = 2; i <= top; i++) int j = 2 * i; while (j <= N) a[j] = false; j += i; for (int i = 2; i <= N; i++) if (a[i]) System.out.printf("%d ", i); System.out.printf("\n"); Primes.java 20

21 Benchmarks Find the primes up to 123,456,789 Using Sieve of Eratosthenes Repeated ten Imes Disabled console output for Iming Language Compiler Type Tower MacBook Pro ThinkPad x41 C++ Visual Studio 2010 compiled C++ GNU g++ compiled Java javac 1.6.0_26 bytecode C# Visual Studio 2010 bytecode C# Mono bytecode PHP (only to 12,345,678) 1 GB memory interpreted

22 Summary Deploying your program Compiled to naive code Compiled to byte code Before you deploy Just- in- Ime based on source Interpreted Benchmark results NaIve and intermediate byte code, similar Interpreted much slower 22