Re: [algogeeks] Re: double and int
Thanx for the precise information. I was coming from a perspective of safe implementation, when dealing with variables, you might not always know whether the values to be compared will fall under the exact floating point representation, so the safe way to go might always be to use the 1.0e-5 method or go with library functions. You see any problem with this too ? Programmers should realize their critical importance and responsibility in a world gone digital. They are in many ways similar to the priests and monks of Europe's Dark Ages; they are the only ones with the training and insight to read and interpret the scripture of this age. On Fri, Jan 7, 2011 at 4:15 AM, Dave dave_and_da...@juno.com wrote: I don't think your example with == would ever fail. According to the IEEE floating point standard, integers within the dynamic range of the number type must be represented exactly and must compare as equal. Furthermore, the four basic operations on integers within the dynamic range of the floating point number type that have integer results within that dynamic range must be exact. Thus, 25.0 - 5.0, 13.0 + 7.0, 4.0 * 5.0, and 60.0 / 3.0 all must equal 20.0 exactly. Where you run into trouble is when the numbers in question cannot be represented exactly in the finite precision floating point format -- something like this: double d1 = 6.1; double d2 = 11.6; double d3 = 17.7; assert(d1 + d2 == d3); // might fail, and Wrong way to do it !! And your correct and recommended way is missing an absolute value: assert(abs(d1 + d2 - d3) 1.0e-5); // given you assume precision of 1e-5 is the correct and recommended way. Dave On Jan 6, 4:19 pm, Avi Dullu avi.du...@gmail.com wrote: Just to mention, floating point numbers r always compared *for equality* like double d1 = 90.0; double d2 = 90.0; assert(d1 == d2); // might fail, and Wrong way to do !! assert(d1 - d2 1e-5); // given u assume precision of 1e-5, is the correct and recommended way. Programmers should realize their critical importance and responsibility in a world gone digital. They are in many ways similar to the priests and monks of Europe's Dark Ages; they are the only ones with the training and insight to read and interpret the scripture of this age. On Fri, Jan 7, 2011 at 1:47 AM, juver++ avpostni...@gmail.com wrote: Numbers without fractional parts are represented exactly (in a range supported by double). -- You received this message because you are subscribed to the Google Groups Algorithm Geeks group. To post to this group, send email to algoge...@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.comalgogeeks%2bunsubscr...@googlegroups.com algogeeks%2bunsubscr...@googlegroups.com . For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en.- Hide quoted text - - Show quoted text - -- You received this message because you are subscribed to the Google Groups Algorithm Geeks group. To post to this group, send email to algoge...@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.comalgogeeks%2bunsubscr...@googlegroups.com . For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en. -- You received this message because you are subscribed to the Google Groups Algorithm Geeks group. To post to this group, send email to algoge...@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en.
[algogeeks] Re: double and int
@Avi: Whether this is a safe implementation depends in part on whether you want to say that 0.2 == 0.29 because they differ by less than 1.0e-5, even though they differ by 45%. Applying your philosophical boilerplate, you have to use some intelligence even in this type of thing. Dave On Jan 7, 12:51 pm, Avi Dullu avi.du...@gmail.com wrote: Thanx for the precise information. I was coming from a perspective of safe implementation, when dealing with variables, you might not always know whether the values to be compared will fall under the exact floating point representation, so the safe way to go might always be to use the 1.0e-5 method or go with library functions. You see any problem with this too ? Programmers should realize their critical importance and responsibility in a world gone digital. They are in many ways similar to the priests and monks of Europe's Dark Ages; they are the only ones with the training and insight to read and interpret the scripture of this age. On Fri, Jan 7, 2011 at 4:15 AM, Dave dave_and_da...@juno.com wrote: I don't think your example with == would ever fail. According to the IEEE floating point standard, integers within the dynamic range of the number type must be represented exactly and must compare as equal. Furthermore, the four basic operations on integers within the dynamic range of the floating point number type that have integer results within that dynamic range must be exact. Thus, 25.0 - 5.0, 13.0 + 7.0, 4.0 * 5.0, and 60.0 / 3.0 all must equal 20.0 exactly. Where you run into trouble is when the numbers in question cannot be represented exactly in the finite precision floating point format -- something like this: double d1 = 6.1; double d2 = 11.6; double d3 = 17.7; assert(d1 + d2 == d3); // might fail, and Wrong way to do it !! And your correct and recommended way is missing an absolute value: assert(abs(d1 + d2 - d3) 1.0e-5); // given you assume precision of 1e-5 is the correct and recommended way. Dave On Jan 6, 4:19 pm, Avi Dullu avi.du...@gmail.com wrote: Just to mention, floating point numbers r always compared *for equality* like double d1 = 90.0; double d2 = 90.0; assert(d1 == d2); // might fail, and Wrong way to do !! assert(d1 - d2 1e-5); // given u assume precision of 1e-5, is the correct and recommended way. Programmers should realize their critical importance and responsibility in a world gone digital. They are in many ways similar to the priests and monks of Europe's Dark Ages; they are the only ones with the training and insight to read and interpret the scripture of this age. On Fri, Jan 7, 2011 at 1:47 AM, juver++ avpostni...@gmail.com wrote: Numbers without fractional parts are represented exactly (in a range supported by double). -- You received this message because you are subscribed to the Google Groups Algorithm Geeks group. To post to this group, send email to algoge...@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.comalgogeeks%2bunsubscr...@googlegroups.com algogeeks%2bunsubscr...@googlegroups.com . For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en.-Hide quoted text - - Show quoted text - -- You received this message because you are subscribed to the Google Groups Algorithm Geeks group. To post to this group, send email to algoge...@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.comalgogeeks%2bunsubscr...@googlegroups.com . For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en.- Hide quoted text - - Show quoted text - -- You received this message because you are subscribed to the Google Groups Algorithm Geeks group. To post to this group, send email to algoge...@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en.
Re: [algogeeks] Re: double and int
I referred to the accuracy of result *acceptable to one*, if there are cases that 0.2 and 0.29 may occur, and u still want to go with a 1.0e-5 value as a zero equality check, its your code, screw it up. If one knows that such corner cases might come and he decides to discard them, fine, else raise the bar. The problem is always to decide the thresholds and then sticking to them. Also, I chose the value of 1.0e-5 to check equality with 0.... and when I say so, I stand by the point that 0.01999 *is* 0.0 for me, *whatever* may be the %age difference, because values lesser than *1.0e-3* do *not* interest me hence I chose the bar as 1.0e-5 and *not* 1.0e-3. Its an engineering decision, not a programming contest solution to get through an online judge. Programmers should realize their critical importance and responsibility in a world gone digital. They are in many ways similar to the priests and monks of Europe's Dark Ages; they are the only ones with the training and insight to read and interpret the scripture of this age. On Sat, Jan 8, 2011 at 1:35 AM, Dave dave_and_da...@juno.com wrote: @Avi: Whether this is a safe implementation depends in part on whether you want to say that 0.2 == 0.29 because they differ by less than 1.0e-5, even though they differ by 45%. Applying your philosophical boilerplate, you have to use some intelligence even in this type of thing. Dave On Jan 7, 12:51 pm, Avi Dullu avi.du...@gmail.com wrote: Thanx for the precise information. I was coming from a perspective of safe implementation, when dealing with variables, you might not always know whether the values to be compared will fall under the exact floating point representation, so the safe way to go might always be to use the 1.0e-5 method or go with library functions. You see any problem with this too ? Programmers should realize their critical importance and responsibility in a world gone digital. They are in many ways similar to the priests and monks of Europe's Dark Ages; they are the only ones with the training and insight to read and interpret the scripture of this age. On Fri, Jan 7, 2011 at 4:15 AM, Dave dave_and_da...@juno.com wrote: I don't think your example with == would ever fail. According to the IEEE floating point standard, integers within the dynamic range of the number type must be represented exactly and must compare as equal. Furthermore, the four basic operations on integers within the dynamic range of the floating point number type that have integer results within that dynamic range must be exact. Thus, 25.0 - 5.0, 13.0 + 7.0, 4.0 * 5.0, and 60.0 / 3.0 all must equal 20.0 exactly. Where you run into trouble is when the numbers in question cannot be represented exactly in the finite precision floating point format -- something like this: double d1 = 6.1; double d2 = 11.6; double d3 = 17.7; assert(d1 + d2 == d3); // might fail, and Wrong way to do it !! And your correct and recommended way is missing an absolute value: assert(abs(d1 + d2 - d3) 1.0e-5); // given you assume precision of 1e-5 is the correct and recommended way. Dave On Jan 6, 4:19 pm, Avi Dullu avi.du...@gmail.com wrote: Just to mention, floating point numbers r always compared *for equality* like double d1 = 90.0; double d2 = 90.0; assert(d1 == d2); // might fail, and Wrong way to do !! assert(d1 - d2 1e-5); // given u assume precision of 1e-5, is the correct and recommended way. Programmers should realize their critical importance and responsibility in a world gone digital. They are in many ways similar to the priests and monks of Europe's Dark Ages; they are the only ones with the training and insight to read and interpret the scripture of this age. On Fri, Jan 7, 2011 at 1:47 AM, juver++ avpostni...@gmail.com wrote: Numbers without fractional parts are represented exactly (in a range supported by double). -- You received this message because you are subscribed to the Google Groups Algorithm Geeks group. To post to this group, send email to algoge...@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.comalgogeeks%2bunsubscr...@googlegroups.com algogeeks%2bunsubscr...@googlegroups.com algogeeks%2bunsubscr...@googlegroups.com . For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en.-Hide quoted text - - Show quoted text - -- You received this message because you are subscribed to the Google Groups Algorithm Geeks group. To post to this group, send email to algoge...@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.comalgogeeks%2bunsubscr...@googlegroups.com
[algogeeks] Re: double and int
On my computer k == p. -- You received this message because you are subscribed to the Google Groups Algorithm Geeks group. To post to this group, send email to algoge...@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en.
Re: [algogeeks] Re: double and int
not always. well , i got some problem using that approachwhen the output is coming out of some library function , this doesn't qualify always i wlll find an example by tomorrow. On Thu, Jan 6, 2011 at 11:48 PM, juver++ avpostni...@gmail.com wrote: On my computer k == p. -- You received this message because you are subscribed to the Google Groups Algorithm Geeks group. To post to this group, send email to algoge...@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.comalgogeeks%2bunsubscr...@googlegroups.com . For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en. -- You received this message because you are subscribed to the Google Groups Algorithm Geeks group. To post to this group, send email to algoge...@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en.
Re: [algogeeks] Re: double and int
Numbers without fractional parts are represented exactly (in a range supported by double). -- You received this message because you are subscribed to the Google Groups Algorithm Geeks group. To post to this group, send email to algoge...@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en.
Re: [algogeeks] Re: double and int
Just to mention, floating point numbers r always compared *for equality* like double d1 = 90.0; double d2 = 90.0; assert(d1 == d2); // might fail, and Wrong way to do !! assert(d1 - d2 1e-5); // given u assume precision of 1e-5, is the correct and recommended way. Programmers should realize their critical importance and responsibility in a world gone digital. They are in many ways similar to the priests and monks of Europe's Dark Ages; they are the only ones with the training and insight to read and interpret the scripture of this age. On Fri, Jan 7, 2011 at 1:47 AM, juver++ avpostni...@gmail.com wrote: Numbers without fractional parts are represented exactly (in a range supported by double). -- You received this message because you are subscribed to the Google Groups Algorithm Geeks group. To post to this group, send email to algoge...@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.comalgogeeks%2bunsubscr...@googlegroups.com . For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en. -- You received this message because you are subscribed to the Google Groups Algorithm Geeks group. To post to this group, send email to algoge...@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en.
[algogeeks] Re: double and int
I don't think your example with == would ever fail. According to the IEEE floating point standard, integers within the dynamic range of the number type must be represented exactly and must compare as equal. Furthermore, the four basic operations on integers within the dynamic range of the floating point number type that have integer results within that dynamic range must be exact. Thus, 25.0 - 5.0, 13.0 + 7.0, 4.0 * 5.0, and 60.0 / 3.0 all must equal 20.0 exactly. Where you run into trouble is when the numbers in question cannot be represented exactly in the finite precision floating point format -- something like this: double d1 = 6.1; double d2 = 11.6; double d3 = 17.7; assert(d1 + d2 == d3); // might fail, and Wrong way to do it !! And your correct and recommended way is missing an absolute value: assert(abs(d1 + d2 - d3) 1.0e-5); // given you assume precision of 1e-5 is the correct and recommended way. Dave On Jan 6, 4:19 pm, Avi Dullu avi.du...@gmail.com wrote: Just to mention, floating point numbers r always compared *for equality* like double d1 = 90.0; double d2 = 90.0; assert(d1 == d2); // might fail, and Wrong way to do !! assert(d1 - d2 1e-5); // given u assume precision of 1e-5, is the correct and recommended way. Programmers should realize their critical importance and responsibility in a world gone digital. They are in many ways similar to the priests and monks of Europe's Dark Ages; they are the only ones with the training and insight to read and interpret the scripture of this age. On Fri, Jan 7, 2011 at 1:47 AM, juver++ avpostni...@gmail.com wrote: Numbers without fractional parts are represented exactly (in a range supported by double). -- You received this message because you are subscribed to the Google Groups Algorithm Geeks group. To post to this group, send email to algoge...@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.comalgogeeks%2bunsubscr...@googlegroups.com . For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en.- Hide quoted text - - Show quoted text - -- You received this message because you are subscribed to the Google Groups Algorithm Geeks group. To post to this group, send email to algoge...@googlegroups.com. To unsubscribe from this group, send email to algogeeks+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/algogeeks?hl=en.
