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Re: Greetings from New member

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  • John Knott
    Regarding Power of Pi Benchmark find all the primes up to 10,000,000 with sieve program (no floating point involved) written in C compiled on target platform
    Message 1 of 5 , Nov 8, 2012
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      Regarding Power of Pi

      Benchmark find all the primes up to 10,000,000 with sieve program (no floating point involved) written in C compiled on target platform no optisimation.
      Pi 9 secs
      XP 1.8 GB laptop 1.8 sec
      Macbook  .9 sec
      8 core 3.4 GB Xeon .9 sec (but could run 4 copies simultaneously without slowing)


       #include <stdlib.h>
       int main(int argc, char **argv) {
              int     top_value = 10000000;
              int     count     = top_value - 1;
              int     *array    = calloc( top_value + 1, sizeof(int));
              int     i, prime, multiple;
              /* mark each int as potentially prime                                    */
              for (i=2; i <= top_value; ++i) 
                      array[i] = 1;
              /* for each starting prime, mark its every multiple as non-prime         */
              for (prime = 2; prime <= top_value; ++prime)
              {
                      if (array[prime])
                              for (multiple = 2*prime; multiple <= top_value; multiple += prime)
                                      if (array[multiple]) {
                                              array[multiple] = 0;
                                              --count;
                                      }
              }
              /* Now that we have marked all multiples of primes as non-prime, print   */
              /* the remaining numbers that fell through the sieve, and are thus prime */
              for (i=2; i <= top_value; ++i)
              {
              //        if (array[i])
      //                      printf("%d ", i);

        

             }
              printf("\n\n %d primes up to %d found.\n", count, top_value);
              exit(0);
       }



    • gkidsonpetlem
      Thanks, Will check it out. 73. Gordon
      Message 2 of 5 , Nov 10, 2012
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        Thanks, Will check it out.

        73.

        Gordon

        --- In Raspberry_Pi_4-Ham_RADIO@yahoogroups.com, Perry Chamberlain <canoeman@...> wrote:
        >
        > Adafriut makes a nice gps sheil that connects up to R PI, and a active puck antenna that
        > Connect to it.
        > Check out adafruit.com.
        >
        > Ke6anm
        >
        >
        > Sent from my iPad
        >
        > On Nov 7, 2012, at 4:42 AM, "gkidsonpetlem" <gordon@...> wrote:
        >
        > > Hi All.
        > >
        > > I'm Gordon, 2e0KPG, located in South Hampshire, UK.
        > >
        > > I'm a not very experienced Ham, and even less experienced in Linux - I've ordered, but not yet recieved, my RPi. I have little programming experience in programming, but reasonable experience with netwroking and non-standard software in Windows (back to 3.1...)
        > >
        > > I have several ideas for applications for my Pi, I can imagine more than one may be needed in future:
        > >
        > > In Car Entertainment/Navigation - I currently use a butchered
        > > old XP laptop hooked up to a lilliput Touchscreen, but its a
        > > cumbersome setup. Anyone know of a GPS Dongle workw with RPi?
        > >
        > > APRS/Marine AIS Igate - I use both these technologies, but find
        > > coverage locally to me is very limited. I'd like a setup which
        > > recieves AIS and gates to internet, and an APRS Igate to
        > > web/ digipeater on 144.800... Possibly using one of the really
        > > cheap chinese handies as a transciever on ham side?
        > >
        > > Mobile APRS message handler/mapping software/BEacon - Interested
        > > in the TNC that John is working on here... Any chance of adding
        > > a GPS as well??
        > >
        > > So, Its evident my main ham use is APRS - I currently use an old XP toshiba laptop, and one of the Cross-country wireless tnc/tracker (USB version). I then hook it into either my antique Yaesu Ft8100, or my little Alinco handy. The mobile rig in my Land Rover works best, as I find that 5 watts from handy is not quite enough in my area (low-lying, fairly heavily built up, hills inland...)
        > >
        > > In an ideal world, I'd probably build a box containing a TNC/tracker, a 10w transciever (fixed on 144.800) and a Pi (if they turn out to be powerful enough) so I can just plug it into power, an antenna, keyboard, mouse and VDU and off we go... Messaging, tracking, mapping etc all in one box... Anyone done anything similar?
        > >
        > > Anyways,
        > > That's me, and what I'm working on...
        > >
        > > 73
        > > Gordon 2E0KPG
        > >
        > >
        >
      • Brian Jones
        The fix for sound to work well as a media centre is to use HDMI :) HDMI sound is excellent but the built in analog sound drivers crackle badly every time
        Message 3 of 5 , Nov 11, 2012
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          The 'fix' for sound to work well as a media centre is to use HDMI :)  HDMI sound is excellent but the built in analog sound drivers crackle badly every time they are started and stopped. AFAIK there has not been a fix for this and iti s supposed to be quite hard to ramp up the Alsa volume on starting a sound stream.

          Normally to change soundcards in linux you can use Alsamixer - I haven't got an external soundcard for my shack Pi yet (the other PI is indeed a media centre using HDMI for both sound and video) so I haven't tried this. I will be interested in your results when you get an external USB sound card working to know whether the Alsa crackling problem is only on the built-in card or whether it occurs on USB cards too. I've been playing about with speech synth and the startup-stop noise is annoying.

          Brian G0UKB
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