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I have that question of how it works ifin low level programming.

If so, it checks the RAM by going through all the addresses that contain it.

I have a doubt in wolfram mathematica. What happens is that I have an array of data and I can generate a espectrograma, what I need is to generate this same spectrogram in 3 dimensions,

2D spectrogram

3D spectrogram (what I want to obtain)

What I want is to achieve something like in the following image

I have achieved it with files .WAVbut not with an excel column with data, which I import into mathematica, I only managed to apply filters and do the spectrograma2D. If someone could give me some help I would appreciate it. Thank you very much.

Edit (I'll add what I have regarding the doubt)

I am using the code that is in the following link, but I think I do not understand the input parameters for the function well, I cannot get it to work for the .csv file . It is probable that I am doing everything wrong and this is not the function that I should use, I have also tried with ListPointPlot3D without results (I can only graph the spectrogram in 2D), but here they import a .WAV file

https://mathematica.stackexchange.com/questions/4017/computing-and-plotting-a-spectrogram-in-mathematica

Attached is the link of the noise.scv file (file of values ​​separated by commas) which is the one I need to graph

https://mega.nz/#!P912VDIT!cRuug34tTVqFO41bc4hhepLfxk4jV5mYCJjwfeTYvLI

And finally the lines of code to import the file to Wolfram

datosExcel = Import["C:\\ruta_del_archivo.csv"]
datosExcel = datosExcel[[All, 1]]

I am trying to alphabetize a variable of type array in the following way:

Code

$palabras = array(
    'así',
    'alfabeto',
    'alfabético',
    'año',
);

sort($palabras);
var_export($palabras);

Result

array (
  0 => 'alfabeto',
  1 => 'alfabético',
  2 => 'así',
  3 => 'año',
)

But as you can see, it doesn't work correctly with the accents and the "ñ", which should be sorted as if the accents weren't there, and with "n" < "ñ" < "o".

How can I do to sort them alphabetically without using external libraries?

I just did a commit:

git commit -m "este es un comentario"

However, I have suddenly realized that this message is not correct. Can I modify it? If yes, how?

If I write again git commit -m "un nuevo comentario"it will make another commit instead of modifying the one I already did.

Here is a very peculiar piece of C++ code. For some strange reason sorting the data miraculously causes the code to run 3 times faster.

#include <algorithm>
#include <ctime>
#include <iostream>

int main()
{
    // Generate data
    const unsigned arraySize = 32768;
    int data[arraySize];

    for (unsigned c = 0; c < arraySize; ++c)
        data[c] = std::rand() % 256;

    // !!! Con esto el siguiente bucle se ejecuta más rápido.
    std::sort(data, data + arraySize);

    // Test
    clock_t start = clock();
    long long sum = 0;

    for (unsigned i = 0; i < 100000; ++i)
    {
        // Primary loop
        for (unsigned c = 0; c < arraySize; ++c)
        {
            if (data[c] >= 128)
                sum += data[c];
        }
    }

    double elapsedTime = static_cast<double>(clock() - start) / CLOCKS_PER_SEC;

    std::cout << elapsedTime << std::endl;
    std::cout << "sum = " << sum << std::endl;
}

• Without std::sort(data, data + arraySize);, the code runs in 12.41 seconds.
• With the data sorted it runs in 3.82 seconds.

At first I thought it might be a language or compiler anomaly. So I tried in Java :

import java.util.Arrays;
import java.util.Random;

public class Main
{
    public static void main(String[] args)
    {
        // Generate data
        int arraySize = 32768;
        int data[] = new int[arraySize];

        Random rnd = new Random(0);
        for (int c = 0; c < arraySize; ++c)
            data[c] = rnd.nextInt() % 256;

        // !!! Con esto el siguiente bucle se ejecuta más rápido.
        Arrays.sort(data);

        // Test
        long start = System.nanoTime();
        long sum = 0;

        for (int i = 0; i < 100000; ++i)
        {
            // Primary loop
            for (int c = 0; c < arraySize; ++c)
            {
                if (data[c] >= 128)
                    sum += data[c];
            }
        }

        System.out.println((System.nanoTime() - start) / 1000000000.0);
        System.out.println("sum = " + sum);
    }
}

Which gives similar but less extreme results. 10.7 and 6.2 seconds.

At first I thought it might have to do with sorting the data getting it into the cache, and then I realized that the data had just been generated with what should already be in the cache before sorting.

• What's going on?
• Why is an ordered array faster than an unordered one?
• The code is calculating the sum of independent terms. The order should not influence, in any case, all the elements are traversed and the same ones are always added, giving the same result, whether they are ordered or not.

This is a question translated from the original in English and adapted to the results it gives on my computer: Why is processing a sorted array faster than an unsorted array? by GManNickG