Jakob, Thank you. I knew I had to be missing some nuance of how to use the library correctly.
Thanks, Anthony On Wednesday, April 18, 2018 at 1:44:13 AM UTC-7, Jakob Borg wrote: > > That is a much too large value to be precisely represented by a float64. > You need more bits, and you need to tell big.Float how many bits that is: > > *https://play.golang.org/p/btm6-_9NQgB > <https://play.golang.org/p/btm6-_9NQgB>* > > //jb > > On 18 Apr 2018, at 09:57, agru...@gmail.com <javascript:> wrote: > > I have been playing with the karatsuba algorithm and was doing some > testing testing to compute the correct values of two large numbers > 3141592653589793238462643383279502884197169399375105820974944592 > and 2718281828459045235360287471352662497757247093699959574966967627. > When working with the math/big package I noticed this oddity, I am sure I > am doing something wrong but hopefully someone can help point it out. If > notice from below the value out of big.NewFloat(myFloat) does not match the > value from printing out g. It also does not match if I print using > g.Float64() and then print the value from that. Should not this be the same > thing in and the same thing out? Thanks in advance. > > // > 8539734222673567065463550869546574495034888535765114961879601127067743044893204848617875072216249073013374895871952806582723184 > > - correct > // > 8539734222673566930176750436921930623970378254642185393758656420093500067115747270318696482879857934897660315084890343252951040 > > - incorrect but this is what I get with the big.NewFloat().Mul > > f := big.NewFloat(float64( > 3141592653589793238462643383279502884197169399375105820974944592)) > //.SetPrec(9223372036854775807) > //.SetMode(big.ToZero) > g := big.NewFloat(float64( > 2718281828459045235360287471352662497757247093699959574966967627)) > //.SetPrec(9223372036854775807) > //.SetMode(big.ToZero) > 2718281828459045271981924443963747209279784634148078442319446016.000000 > this is what g prints vs what was input > > h := big.NewFloat(1).Mul(f, g).SetPrec(9223372036854775807) > //.SetMode(big.ToZero) > > a := float64( > 3141592653589793238462643383279502884197169399375105820974944592) * > float64(2718281828459045235360287471352662497757247093699959574966967627) > > fmt.Printf("%f\n", f) > fmt.Printf("%f\n", g) //prints out > 2718281828459045271981924443963747209279784634148078442319446016.000000 > fmt.Printf("%f\n", a) > fmt.Printf("%f\n", h) > > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts...@googlegroups.com <javascript:>. > For more options, visit https://groups.google.com/d/optout. > > > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. For more options, visit https://groups.google.com/d/optout.
