Subject:
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RCX Firmware speed versus legOS
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Newsgroups:
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lugnet.robotics
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Date:
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Thu, 11 Apr 2002 17:23:20 GMT
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Viewed:
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456 times
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The discussion about the Firmware speed is intresting indeed. So I did a
fast, by no means representative, reserch. The following program is a legOS
program reading the light sensor, calculating some values and printing the
elapsed time:
------------------------------------------------------
#include <conio.h>
#include <unistd.h>
#include <dsensor.h>
int main()
{
int i;
int max, min, mean;
int value;
time_t time;
max = 0;
min = 5000;
mean = 0;
value = 0;
ds_active( &SENSOR_2 );
time = sys_time;
for( i = 1; i <= 10000; i++ ) {
value = LIGHT_2; // for empty loop comment out this line
if( max < value ) max = value;
if( min > value ) min = value;
mean = ( mean * 3 - mean + value ) / 3;
}
time = sys_time - time;
lcd_int( time );
return 0;
}
----------------------------------------------------------
It took 0.211 sec. running empty, i.e. without reading the sensor but only
doing calculations, and 1.113 sec. with reading the sensor. So I can assume
that reading 10000 light values takes about 1 second.
I tried the same with the following nqc program:
----------------------------------------------------------
task main()
{
int i;
int max, min, mean;
int value;
int time;
max = 0;
min = 5000;
mean = 0;
value = 0;
SetUserDisplay( 0, 0 );
SetSensor( SENSOR_2, SENSOR_LIGHT );
ClearTimer( 0 );
for( i = 1; i <= 10000; i++ ) {
value = SENSOR_2;
if( max < value ) max = value;
if( min > value ) min = value;
mean = ( mean * 3 - mean + value ) / 3;
}
time = Timer( 0 );
SetUserDisplay( time, 0 );
until( false );
}
------------------------------------------------------------
This program is a direct conversion of the legOS version. The empty loop
took 322.3 sec.
So it can safely be assumed that the interpreted program runs about the
factor 300 slower than the assembly program generated by gcc. But with
reading the light sensor, the program only took 350.4 sec., giving about 30
secs for 10000 light sensor reads.
This result seems reasonable. The pure action of reading the light sensor
is roughly the same for legOS and the Firmware because reading an active
sensor value is very time critical.
Inspecting only the light sensor read, legOS is 30 times faster then a
Firmware program. But reading the sensor alone is not useful most of the
time. If one has do do some math with the results, legOS runs up and away.
The numbers for comparision:
empty with light reading
LegOS program: 0.211 1.113
Firmware program: 322.3 350.4
I would be pleased to get the results for my test program from lejos and
pbforth too, but I can't write a program in forth and are slow with java.
Any volunteers?
Bye
Mike
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Message has 1 Reply:
 | | Re: RCX Firmware speed versus legOS
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| "Michael Obenland" <obenland@t-online.de> wrote in message news:GuEtHr.M39@lugnet.com... (...) but only (...) assume (...) I was surprized at the wide disparity between 'empty loop' and loop with 'reading the sensor'. I suspect there is significant (...) (22 years ago, 11-Apr-02, to lugnet.robotics)
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