Random Photo Selection

By wavemaker
Feb 2, 2010
  1. Gooday all. No one is going to die if this question doesn't get answered, I am just curious. When I set my screen saver to display photos from "My Pics" I get the option for it to select which photos to display at random. So I have selected this option and sure enough away it goes and does just that,almost. I notice that some photos turn up more often than others and some I have never seen at all. I have had this on my machine in different guises for quite a long time and I am certain that some photos just never get shown. So, my question is. How in Hades does this random thingy work. Thanks in advance, James.
  2. Archean

    Archean TechSpot Paladin Posts: 5,682   +86

    Well it randomly picks up the picture it want to show for the time specified, now depending upon time and power settings (as if the PC is on idle for too long it may go into standby or turn off monitor screen etc.), if you allow to run it for longer periods of time you may notice some of those pictures show up.
  3. Ultiweap

    Ultiweap TS Enthusiast Posts: 606

    First this may be due of the format of some photos or resolution. If the does not meet the requirements windows may not display them and that's why some of them did not display.
  4. Archean

    Archean TechSpot Paladin Posts: 5,682   +86

    I've dumped all the wallpapers I have in a single folder; and when the screensaver is running it just picks up random pictures to show disregarding picture resolution.
  5. wavemaker

    wavemaker TS Rookie Topic Starter

    Thank you all for those most informative replies. I still want to know how it randomly picks a photo to show. there is a tiny chance that if it is totally random it could show the same pic every 5 minutes or even every second photo. So I figure there must be some sort of instruction to the computer to pick far and wide. Like I said, no one is going to die. I would just like to understand the process better. Thanks again. James.
  6. Archean

    Archean TechSpot Paladin Posts: 5,682   +86

    Random numbers are useful for a variety of purposes, such as generating data encryption keys, simulating and modeling complex phenomena and for selecting random samples from larger data sets. They have also been used aesthetically, for example in literature and music, and are of course ever popular for games and gambling. When discussing single numbers, a random number is one that is drawn from a set of possible values, each of which is equally probable, i.e., a uniform distribution. When discussing a sequence of random numbers, each number drawn must be statistically independent of the others.

    With the advent of computers, programmers recognized the need for a means of introducing randomness into a computer program. However, surprising as it may seem, it is difficult to get a computer to do something by chance. A computer follows its instructions blindly and is therefore completely predictable. (A computer that doesn't follow its instructions in this manner is broken.) There are two main approaches to generating random numbers using a computer: Pseudo-Random Number Generators (PRNGs) and True Random Number Generators (TRNGs). The approaches have quite different characteristics and each has its pros and cons.

    As the word ‘pseudo’ suggests, pseudo-random numbers are not random in the way you might expect, at least not if you're used to dice rolls or lottery tickets. Essentially, PRNGs are algorithms that use mathematical formulae or simply precalculated tables to produce sequences of numbers that appear random. A good example of a PRNG is the linear congruential method. A good deal of research has gone into pseudo-random number theory, and modern algorithms for generating pseudo-random numbers are so good that the numbers look exactly like they were really random.

    The basic difference between PRNGs and TRNGs is easy to understand if you compare computer-generated random numbers to rolls of a die. Because PRNGs generate random numbers by using mathematical formulae or precalculated lists, using one corresponds to someone rolling a die many times and writing down the results. Whenever you ask for a die roll, you get the next on the list. Effectively, the numbers appear random, but they are really predetermined. TRNGs work by getting a computer to actually roll the die — or, more commonly, use some other physical phenomenon that is easier to connect to a computer than a die is.

    As TRNG's efficiency to generating random numbers in comparison with pseudo random generating method is poorer. They are also nondeterministic, meaning that a given sequence of numbers cannot be reproduced, although the same sequence may of course occur several times by chance.

    Therefore, as far as i can understand something similar to this is in action with regard to windows screensaver; hence the randomness algorithm used here is generating not so random results.

    I hope someone will come up with better explanation or correct me if i am wrong here.
  7. wavemaker

    wavemaker TS Rookie Topic Starter

    Thank you for that detailed response Archean. That has filled a gap for sure. I will now go hunting with a lot more knowledge than I had 5 minutes ago. James
  8. Archean

    Archean TechSpot Paladin Posts: 5,682   +86

    You are most welcome, and I'm glad that this information was something useful for you.
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