Testing different solutions for counting the occurrences of a given character inside a 100mb file (comparing performances between ack, STL streams on disk and STL streams with a file saved on a ramdisk).

100mb.cpp

#include <iostream>
#include <fstream>
#include <cstdlib>
#include <ctime>
using namespace std;

void generate(char * filename, string range)
{
    int rangeLength = range.length();
    srand (time(NULL));

    ofstream out;
    out.open(filename);
    for (int i=0; i<104857600; i++)
        if (i%(rand()%10+60)==0)
            out << "\n";
        else
            out << range[rand() % rangeLength];
    out.close();
}

void count(char * filename, char search)
{
    int counter = 0;
    ifstream in;
    in.open(filename);
    while (in.good())
        if (search == (char) in.get())
            counter++;
    in.close();
    cout << counter << "\n";
}

void read(char * filename)
{
    ifstream in;
    in.open(filename);
    while (in.good())
        in.get();
    in.close();
}

void usage(char * filename)
{
    cout << "Usage:\t" << filename << " command file [char]\n\n"
         "\t" << filename << " generate file\t"
         << "Generate a 100mb file\n"
         "\t" << filename << " read file\t"
         << "Read a file\n"
         "\t" << filename << " count file char\t"
         << "Count the occurrences of char inside file\n";
}

int main(int argc, char *argv[])
{
    string range = "0123456789abcdefghijklmnopqrstuvwxyz (){}[]*+-/=<>#;.,";

    switch(argc) {
    case 3:
        if (argv[1]==string("generate"))
            generate(argv[2], range);
        else if (argv[1]==string("read"))
            read(argv[2]);
        else
            usage(argv[0]);
        break;
    case 4:
        if (argv[1]==string("count"))
            count(argv[2], argv[3][0]);
        else
            usage(argv[0]);
        break;
    default:
        usage(argv[0]);
        break;
    }
}

results.txt

[framp@a8 100mb]$ sh test.sh
Compiling tool...
Generating file...
Mounting a ramdisk...

Occurences:
FGREP+WC: 1913217
ACK: 899832
COUNT: 1913217

Testing...
ACK
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
899832
	Samples:	50 
	Mean Avg:	3.6552

READ
	Samples:	50 
	Mean Avg:	3.1254

COUNT
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
	Samples:	50 
	Mean Avg:	3.0966

READRAMDISK
	Samples:	50 
	Mean Avg:	1.3938

COUNTRAMDISK
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
1913217
	Samples:	50 
	Mean Avg:	1.5296

test.sh

#!/bin/bash

#Calculate the mean average of wall clock time from multiple /usr/bin/time results.
#http://stackoverflow.com/questions/8215482/mean-running-time-over-a-number-of-runs
function timeAverage {
	file=${1}
	cnt=0

	if [ ${#file} -lt 1 ]; then
		echo "you must specify a file containing output of /usr/bin/time results"
		exit 1
	elif [ ${#file} -gt 1 ]; then
		samples=(`grep --color=never  real ${file} | awk '{print $2}' | cut -dm -f2 | cut -ds -f1`)

		for sample in `grep --color=never real ${file} | awk '{print $2}' | cut -dm -f2 | cut -ds -f1`; do
			cnt=$(echo ${cnt}+${sample} | bc -l)
		done

		# Calculate the 'Mean' average (sum / samples).
		mean_avg=$(echo ${cnt}/${#samples[@]} | bc -l)
		mean_avg=$(echo ${mean_avg} | cut -b1-6)

		printf "\tSamples:\t%s \n\tMean Avg:\t%s\n\n" ${#samples[@]} ${mean_avg}
	fi 
}

#Do 50 tests and calculate the average
function timeTest {
	
	echo $1
	shift
	for i in {1..50}; do 
		sudo echo 3 | sudo tee /proc/sys/vm/drop_caches > /dev/null
		time -a -o times.log -p $@
	done
	timeAverage times.log
	rm times.log
}

if [ 100mb.cpp -nt 100mb ]; then
	echo "Compiling tool..."
	g++ 100mb.cpp -o 100mb
	chmod +x 100mb
fi
echo "Generating file..."
./100mb generate 100mb.txt
echo "Mounting a ramdisk..."
mkdir -p ramdisk
sudo mount -t tmpfs -o nodev,nosuid,noexec,nodiratime,size=150M none ramdisk
cp 100mb.txt ramdisk/100mb.txt
echo ""

echo "Occurrences:"
echo "FGREP+WC:" $(fgrep -o ')' "100mb.txt" | wc -l)
echo "ACK:" $(ack -c '\)' "100mb.txt")
echo "COUNT:" $(./100mb count "100mb.txt" ')')
echo ""

echo "Testing..."
timeTest "ACK" ack -c '\)' 100mb.txt
timeTest "READ" ./100mb read "100mb.txt"
timeTest "COUNT" ./100mb count "100mb.txt" ')'
timeTest "READRAMDISK" ./100mb read "ramdisk/100mb.txt"
timeTest "COUNTRAMDISK" ./100mb count "ramdisk/100mb.txt" ')'

rm -f "ramdisk/100mb.txt" "100mb.txt"
sudo umount ramdisk
rm -rf ramdisk