doing floating operations using integer operations

This is a discussion on doing floating operations using integer operations within the C Programming forums, part of the General Programming Boards category; How one can do floating point operations with using only integer operations e.g. finding r in x^2 + y^2 = ...

  1. #1
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    Lightbulb doing floating operations using integer operations

    How one can do floating point operations with using only integer operations e.g. finding r in x^2 + y^2 = r^2 with out using any floating point operations


    Thanks

  2. #2
    Mad OnionKnight's Avatar
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    x*x + y*y? Don't think there's any different approach to sqrt() though.
    In situations where you need multiplication you can use fractions instead of floats, e.g (x*355)/113 instead of x*pi or (x*95)/100 instead of x*0.95. This introduces a possible problem with integer overflow though.

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    Frequently Quite Prolix dwks's Avatar
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    Why don't you want to use floating point numbers?
    dwk

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    Cat without Hat CornedBee's Avatar
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    You could use fixed-point math. But you'll have to write pretty much everything yourself.
    All the buzzt!
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  5. #5
    Super Moderator VirtualAce's Avatar
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    Floating point on modern machines is a tad faster than integer ops. No need for fixed point anymore.

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    How one can do floating point operations ... ... ... with out using any floating point operations



    unsigned long long comes to mind.
    Code:
    #include <stdio.h>
    
    void J(char*a){int f,i=0,c='1';for(;a[i]!='0';++i)if(i==81){
    puts(a);return;}for(;c<='9';++c){for(f=0;f<9;++f)if(a[i-i%27+i%9
    /3*3+f/3*9+f%3]==c||a[i%9+f*9]==c||a[i-i%9+f]==c)goto e;a[i]=c;J(a);a[i]
    ='0';e:;}}int main(int c,char**v){int t=0;if(c>1){for(;v[1][
    t];++t);if(t==81){J(v[1]);return 0;}}puts("sudoku [0-9]{81}");return 1;}

  7. #7
    pronounced 'fib' FillYourBrain's Avatar
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    Quote Originally Posted by jafet



    unsigned long long comes to mind.
    ?

    how does a 64 bit integer solve his problem?
    "You are stupid! You are stupid! Oh, and don't forget, you are STUPID!" - Dexter

  8. #8
    Frequently Quite Prolix dwks's Avatar
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    You use fixed point math, which, as Bubba pointed out, isn't much faster anymore.

    An example is storing monetary values in an integer, the cent value in the first two digits, and dollars in the other digits. To store $14.68, you would store 1468. There's a fixed point -- the decimal point is always in the second place.
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


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  9. #9
    ATH0 quzah's Avatar
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    Sometimes you need accuracy over speed. Floating point isn't accurate.


    Quzah.
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  10. #10
    Frequently Quite Prolix dwks's Avatar
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    Like with money. You wouldn't want ten thousand 99 dollar items to cost $9900.13, now would you?
    dwk

    Seek and ye shall find. quaere et invenies.

    "Simplicity does not precede complexity, but follows it." -- Alan Perlis
    "Testing can only prove the presence of bugs, not their absence." -- Edsger Dijkstra
    "The only real mistake is the one from which we learn nothing." -- John Powell


    Other boards: DaniWeb, TPS
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    My website: http://dwks.theprogrammingsite.com/
    Projects: codeform, xuni, atlantis, nort, etc.

  11. #11
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    Of course I would! That'd be nearly 99% off the store price! It's always nice to buy in bulk Unless you meant, of course, 99 cents per item.
    Code:
    #include <stdio.h>
    
    void J(char*a){int f,i=0,c='1';for(;a[i]!='0';++i)if(i==81){
    puts(a);return;}for(;c<='9';++c){for(f=0;f<9;++f)if(a[i-i%27+i%9
    /3*3+f/3*9+f%3]==c||a[i%9+f*9]==c||a[i-i%9+f]==c)goto e;a[i]=c;J(a);a[i]
    ='0';e:;}}int main(int c,char**v){int t=0;if(c>1){for(;v[1][
    t];++t);if(t==81){J(v[1]);return 0;}}puts("sudoku [0-9]{81}");return 1;}

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