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Linear regression on atmega 128L

i, Having found out that the avr-gcc lib supports floats and handles them quite gracefully, I tried porting my linear regression code from desktop on to the atmega 128L, more or less as is. For testing i used the same table of X and Y values as sample inputs to the algorithm.

Now I am using microsecond granularity as input to the regression engine and since the values are fairly large - and since there are sum of products- I get fairly large numbers (If i do the same on my desktop, the biggest number i get is sumXSq=7260107358192.000000). Hence i decided to use long long (64 bit!) as follows: (i know long long and int64_t are the same but i am clutching at straws) typedef struct regressTbl{ int16_t n ; long long sumXY; int64_t sumX,sumY; long long sumXSquared; }regTable;

and then I added the sum for each point from the table. It should be okay.. but it wasnt :( .. here is a manual version of the final values:

table.sumX = 12338578; table.sumY = -3336078; table.sumXSquared = 7260107358192;

Reply to
Intiha
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On 3 Apr 2005 17:12:31 -0700, "Intiha" wrote in comp.arch.embedded:

Next time please indicate the lines in the source code that the numbers in the error messages point to.

It looks like your compiler is not completely C99 conforming and supports the 64-bit long long type as some sort of extension. A conforming C99 compiler will automatically make literal constants long long if they are too large to fit in a long.

I'm not familiar with the avr-gcc port, but you could try making your constants explicitly long long with the LL suffix. That is:

table.sumXSquared = 7260107358192LL;

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Jack Klein
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Reply to
Jack Klein

Thank oyu for your reply.... I actually did point to the lines ( like this

Reply to
Intiha

Well, then don't do that. Give it the correct format specifier for long long, or print the number split up into 2 32-bit longs. There's absolutely no sense in trying to debug results as long as you don't really know what the inputs were.

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Hans-Bernhard Broeker (broeker@physik.rwth-aachen.de)
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Reply to
Hans-Bernhard Broeker

thats the problem... I have gone throught avr-libc manual and the closest it come to (for vprintf) is to use %ld or %li for long int types... nothing for long long- Does any one know the correct flag?.. but i will try and get the split 32 bit values as soon as i get to the office.

Regards Affan

Reply to
Intiha

Please quote enough of whatever you are replying to to provide a context. Your article should stand on its own. To do this on the broken google interface, see my sig lines below.

long long is a C99 creation. Are you sure your AVR library is C99 compliant? I rather doubt it. gcc may well accept a -std=c99, but it won't help without the library.

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Reply to
CBFalconer

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