compute RTT values

index.c

/**
 * compute RTT values
 * (DevRTT, EstimatedRTT, TimeoutInterval)
 * @author shj <https://github.com/Gumball12>
 * */

// import module
#include <stdio.h>
#include <stdlib.h> // for absolute value function 'abs'

// define constants
#define ALPHA 0.125
#define BETA 0.25

/**
 * compute RTT values
 * !WARN: this function is a 'recursive' function
 * @param sampleRTTs sampleRTT value array
 * @param prevEstimatedRTT previous estimatedRTT value
 * @param prevDevRTT previous devRTT value
 * */
void calcRTT(int *sampleRTTs, double prevEstimatedRTT, double prevDevRTT) {
        // check sampleRTT array
        if (sampleRTTs[0] == -1) { // end of recursion
                return;
        }

        // compute RTT values
        double estimatedRTT = (1 - ALPHA) * prevEstimatedRTT + ALPHA * sampleRTTs[0];
        double devRTT = (1 - BETA) * prevDevRTT + BETA * abs(sampleRTTs[0] - estimatedRTT);
        double timeoutInterval = estimatedRTT + 4 * devRTT;

        // print RTT values
        printf("estimatedRTT: %lf, devRTT: %lf, timeoutInterval: %lf\n", estimatedRTT, devRTT, timeoutInterval);

        // recursion
        calcRTT(sampleRTTs + 1, estimatedRTT, prevDevRTT);
}

/**
 * entry point
 * */
int main(void) {
        // init values
        int sampleRTTs[] = { 106, 120, 140, 90, 115, -1 };
        double initEstimatedRTT = 100;

        // start calculation
        calcRTT(sampleRTTs, initEstimatedRTT, 10);
}