Re: [julia-users] Numer of ones in bitstype
Using the leading_zeros hint, I can access the first bit as follows: firstbit(x) = leading_ones(x) > 0 This seems indirect however. And the code native also seems longer then what I would have hoped for: @code_native firstbit(x) .text Filename: In[78] Source line: 1 pushq %rbp movq%rsp, %rbp Source line: 1 notb%dil movzbl %dil, %eax movl$15, %ecx bsrl%eax, %eax cmovel %ecx, %eax xorl$7, %eax testb %al, %al setne %al popq%rbp ret Is there a more efficient way in julia? On Friday, August 12, 2016 at 2:10:37 PM UTC+2, jw3126 wrote: > > Thank you both! > > On Thursday, August 11, 2016 at 9:17:13 PM UTC+2, Erik Schnetter wrote: >> >> See also "leading_zeros". >> >> -erik >> >> On Thu, Aug 11, 2016 at 1:52 PM, Tom Breloff wrote: >> >>> help?> count_ones >>> search: count_ones count_zeros >>> >>> count_ones(x::Integer) -> Integer >>> >>> Number of ones in the binary representation of x. >>> >>> julia> count_ones(7) >>> 3 >>> >>> >>> On Thu, Aug 11, 2016 at 1:48 PM, jw3126 wrote: >>> I have a bitstype and want to know the number of ones in its bit representation as well as the first bit. How to accomplish these in a performant way? >>> >>> >> >> >> -- >> Erik Schnetter >> http://www.perimeterinstitute.ca/personal/eschnetter/ >> >
Re: [julia-users] Numer of ones in bitstype
Using the leading_zeros hint, I can access the first bit as follows: firstbit(x) = leading_ones(x) > 0 Is this the most efficient way to access the first bit in julia? The code native seems longer then what I would have hoped for: @code_native firstbit(0x12) .text Filename: int.jl Source line: 139 pushq %rbp movq%rsp, %rbp Source line: 139 notb%dil movzbl %dil, %eax movl$15, %ecx bsrl%eax, %eax cmovel %ecx, %eax xorl$7, %eax movzbl %al, %eax popq%rbp ret On Friday, August 12, 2016 at 2:10:37 PM UTC+2, jw3126 wrote: > > Thank you both! > > On Thursday, August 11, 2016 at 9:17:13 PM UTC+2, Erik Schnetter wrote: >> >> See also "leading_zeros". >> >> -erik >> >> On Thu, Aug 11, 2016 at 1:52 PM, Tom Breloff wrote: >> >>> help?> count_ones >>> search: count_ones count_zeros >>> >>> count_ones(x::Integer) -> Integer >>> >>> Number of ones in the binary representation of x. >>> >>> julia> count_ones(7) >>> 3 >>> >>> >>> On Thu, Aug 11, 2016 at 1:48 PM, jw3126 wrote: >>> I have a bitstype and want to know the number of ones in its bit representation as well as the first bit. How to accomplish these in a performant way? >>> >>> >> >> >> -- >> Erik Schnetter >> http://www.perimeterinstitute.ca/personal/eschnetter/ >> >
Re: [julia-users] Numer of ones in bitstype
Thank you both! On Thursday, August 11, 2016 at 9:17:13 PM UTC+2, Erik Schnetter wrote: > > See also "leading_zeros". > > -erik > > On Thu, Aug 11, 2016 at 1:52 PM, Tom Breloff > wrote: > >> help?> count_ones >> search: count_ones count_zeros >> >> count_ones(x::Integer) -> Integer >> >> Number of ones in the binary representation of x. >> >> julia> count_ones(7) >> 3 >> >> >> On Thu, Aug 11, 2016 at 1:48 PM, jw3126 > >> wrote: >> >>> I have a bitstype and want to know the number of ones in its bit >>> representation as well as the first bit. How to accomplish these in a >>> performant way? >>> >> >> > > > -- > Erik Schnetter > > http://www.perimeterinstitute.ca/personal/eschnetter/ >
Re: [julia-users] Numer of ones in bitstype
See also "leading_zeros". -erik On Thu, Aug 11, 2016 at 1:52 PM, Tom Breloff wrote: > help?> count_ones > search: count_ones count_zeros > > count_ones(x::Integer) -> Integer > > Number of ones in the binary representation of x. > > julia> count_ones(7) > 3 > > > On Thu, Aug 11, 2016 at 1:48 PM, jw3126 wrote: > >> I have a bitstype and want to know the number of ones in its bit >> representation as well as the first bit. How to accomplish these in a >> performant way? >> > > -- Erik Schnetter http://www.perimeterinstitute.ca/personal/eschnetter/
Re: [julia-users] Numer of ones in bitstype
help?> count_ones search: count_ones count_zeros count_ones(x::Integer) -> Integer Number of ones in the binary representation of x. julia> count_ones(7) 3 On Thu, Aug 11, 2016 at 1:48 PM, jw3126 wrote: > I have a bitstype and want to know the number of ones in its bit > representation as well as the first bit. How to accomplish these in a > performant way? >
[julia-users] Numer of ones in bitstype
I have a bitstype and want to know the number of ones in its bit representation as well as the first bit. How to accomplish these in a performant way?
