Difference between revisions of "Java vs. C"
m (New page: Several people have told me recently that Java runs as fast as C. After repeating this information somewhat, I decided to test it for computer forensics. The test I constructed a test fil...) |
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Revision as of 13:29, 28 May 2009
Several people have told me recently that Java runs as fast as C. After repeating this information somewhat, I decided to test it for computer forensics.
The test I constructed a test file of 4238912226 bytes. The test involved reading the file 4K byte blocks at a time and computing the SHA1 hash of each block.
Here is the C program I used:
#include <stdio.h> #include <stdlib.h> #include <openssl/sha.h> int main(int argc,char **argv) { FILE *f = 0; if(argc!=2){ fprintf(stderr,"usage: %s - compute block hashes (but don't print them)\n"); } f = fopen(argv[1],"r"); if(!f) { perror(argv[1]); exit(1); } while(!feof(f)){ char buf[4096]; unsigned char md[20]; size_t count = fread(buf,1,sizeof(buf),f); SHA_CTX c; SHA_Init(&c); SHA_Update(&c,buf,count); SHA_Final(md,&c); } fclose(f); }
I ran the test 3 times on my Mac Pro (2x2.66 Ghz Dual-Core Intel Xeons, 12GB 667 Mhz DDR2 FB-DIMM memory, 1TB hard drive)
12:59 PM m:~/nps/speedtest$ time ./ctest /realistic.aff real 0m53.443s user 0m25.459s sys 0m6.113s 01:00 PM m:~/nps/speedtest$ time ./ctest /realistic.aff real 0m31.137s user 0m25.327s sys 0m5.650s 01:01 PM m:~/nps/speedtest$ time ./ctest /realistic.aff real 0m31.694s user 0m25.392s sys 0m5.920s 01:02 PM m:~/nps/speedtest$
The first time the file was being read off the disk, the second two trials the file was in memory.
Interestingly, the entire file can be read in around 8 seconds on this hardware:
time dd if=/realistic.aff of=/dev/null bs=4096 1034890+1 records in 1034890+1 records out 4238912226 bytes transferred in 7.786416 secs (544398372 bytes/sec) real 0m7.979s user 0m1.455s sys 0m6.335s 01:22 PM m:~/nps/speedtest$
So how fast is Java? Here is my first Java program:
import java.security.MessageDigest; import java.security.NoSuchAlgorithmException; import java.io.*; //import System.currentTimeMillis; public class jtest { public static void main(String[] args){ long t0 = System.currentTimeMillis(); try { System.out.println("Start"); FileInputStream fis = new FileInputStream(new File(args[0])); while(true){ MessageDigest md = MessageDigest.getInstance("SHA"); byte[] buf = new byte[4096]; int count = fis.read(buf); if(count==-1) break; /*throw new Exception("Done");*/ md.update(buf); byte[] f = md.digest(); } System.out.println("Done"); } catch (IOException e){ System.out.println(e); } catch (NoSuchAlgorithmException e){ System.out.println(e); } long t1 = System.currentTimeMillis(); System.out.printf("Miliseconds to execute: %d\n",t1-t0); } }
Notice that I have the program report how long it takes to run the benchmark, so we can factor out the cost of JVM startup.
01:14 PM m:~/nps/speedtest$ time java jtest /realistic.aff Start Done Miliseconds to execute: 97843 real 1m39.227s user 1m29.803s sys 0m7.687s 01:15 PM m:~/nps/speedtest$ time java jtest /realistic.aff Start Done Miliseconds to execute: 95853 real 1m36.944s user 1m28.722s sys 0m7.189s 01:18 PM m:~/nps/speedtest$
So those are pretty interesting numbers. Java seems to be running 3x slower.