Member Avatar for George_91

I've to make several experiments of some algorithms. I want to send those results to a .txt file

//....
for (count= 1; count<= 20; count++){
//....
std::cout<<exp<<"Time:  "<<duration << " seconds" <<'\n';

ofstream f2;
   f2.open("results.txt", ofstream::out);
		for(int i=0; i<=20; i++){
			f2<<duration<<endl;
}
   f2.close();
}

With this code, I only get the same result repeated several times, instead of saving a result per line. What do I need to modify of this code??

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  • Latest Post Latest Post by MachDelta

Dani AI

Generated

The repeated values come from two separate issues: writing the same duration many times inside a second loop, and reopening the output file in a way that erases earlier results each test. was right that the inner loop is writing duplicates; was right to move the file open outside the test loop. Use a single open (or open with append) and write one line per test. A CSV line with run id, input size and duration makes later analysis easy.

#include <fstream>
#include <iomanip>

// open once (use std::ios::app if you want to append across program runs)
std::ofstream out("results.csv", std::ios::out);
if (!out.is_open()) { /* handle error */ }

out << "run,data_size,algorithm,duration_seconds\n";

for (int run = 1; run <= 20; ++run) {
    // prepare input and run the algorithm; compute duration for this run
    double duration = /* compute per-run duration */;
    int data_size = /* current input size */;
    std::string alg = /* algorithm name */;

    out << run << ',' << data_size << ',' << alg << ','
        << std::fixed << std::setprecision(6) << duration << '\n';
}

out.close();

Troubleshooting checklist:

  • Confirm duration is recomputed inside the test loop (not set once before the loop).
  • Remove any inner loop that writes the same value repeatedly.
  • If you run the program multiple times and want to preserve previous results, open with std::ios::app. Opening with the default std::ios::out truncates the file.
  • Check out.is_open() and test out.fail() after writes; use an absolute path if you can’t find the file (IDE working directories can differ).
  • Print the value to console immediately before writing to the file to verify it changes.

Extras: include descriptive columns (algorithm, input size, run), use std::chrono::high_resolution_clock for timing and std::setprecision for consistent numeric output, and prefer CSV for easy import into spreadsheets or plotting tools.

Recommended Answers

All 3 Replies

Member Avatar for Topi Ojala

What is the purpose of the inner for-loop? That's where you write the same result multiple times.

What do you mean with a result? Your duration variable doesn't change at all during the program. At this moment you are writing 20x20 times duration to results.txt.

Member Avatar for George_91

What is the purpose of the inner for-loop? That's where you write the same result multiple times.

What do you mean with a result? Your duration variable doesn't change at all during the program. At this moment you are writing 20x20 times duration to results.txt.

I've to do 20 tests of each sorting algorithm, with different ammount of data (from 100 to a million integers)

The first loop is for re-running the program 20 times, so I can get 20 different results. It works fine until there.

For my convenience, I want to send those 20 results to a .txt so I can paste them into tables.

The problem is in the ofstream, it sends the same outcome to the .txt file..

Member Avatar for MachDelta

You have to push the results out to the file after every test. By doing the print to file loop after the test loop, you can only print the last result. They need to be within the same loop.

//....
ofstream f2;
f2.open("results.txt", ofstream::out); //Open file

for (count= 1; count<= 20; count++){
//.... Run test
std::cout<<exp<<"Time:  "<<duration << " seconds" <<'\n'; //Print to console
f2<<duration<<endl;     //Print to file
} // End test loop

f2.close();
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