3 ms·

Apparently the Rust compiler produces a slightly different branch-free FizzBuzz[1] involving this delightful snippet: static OUT: &'static [u8] = b"\ 1

Apparently the Rust compiler produces a slightly different branch-free FizzBuzz[1] involving this delightful snippet: static OUT: &'static [u8] = b"\ 1\n2\nFizz\n4\nBuzz\nFizz\n7\n8\nFizz\nBuzz\n11\nFizz\n13\n14\nFizzBuzz\n\ 16\n17\nFizz\n19\nBuzz\nFizz\n22\n23\nFizz\nBuzz\n26\nFizz\n28\n29\nFizzBuzz\n\ 31\n32\nFizz\n34\nBuzz\nFizz\n37\n38\nFizz\nBuzz\n41\nFizz\n43\n44\nFizzBuzz\n\ 46\n47\nFizz\n49\nBuzz\nFizz\n52\n53\nFizz\nBuzz\n56\nFizz\n58\n59\nFizzBuzz\n\ 61\n62\nFizz\n64\nBuzz\nFizz\n67\n68\nFizz\nBuzz\n71\nFizz\n73\n74\nFizzBuzz\n\ 76\n77\nFizz\n79\nBuzz\nFizz\n82\n83\nFizz\nBuzz\n86\nFizz\n88\n89\nFizzBuzz\n\ 91\n92\nFizz\n94\nBuzz\nFizz\n97\n98\nFizz\nBuzz\n"; ... 1: http://chrismorgan.info/blog/rust-fizzbuzz.html http://chrismorgan.info/blog/rust-fizzbuzz.html

eckzow 12y ago
By my reading that implementation was assembled by humans, not the optimizer. Although, there's certainly nothing magical that prevents the optimizer from generating such code. Here's something[1] I just threw together that (ab)uses constexpr to do just that. On my machine, building with: $ clang++ -std=c++14 fizzbuzz.cpp -O2 -S Gives code similar to: main: # @main .cfi_startproc # BB#0: pushq %rax .Ltmp0: .cfi_def_cfa_offset 16 movl $1, %edi movl $_ZL6output, %esi movl $413, %edx # imm = 0x19D callq write xorl %eax, %eax popq %rdx retq .Ltmp1: .size main, .Ltmp1-main .cfi_endproc .type _ZL6output,@object # @_ZL6output .section .rodata,"a",@progbits _ZL6output: .ascii "1\n2\nFizz\n4\nBuzz\nFizz\n7\n8\nFizz\nBuzz\n11\nFizz\n13\n14\nFizzBuzz\n16\n17\nFizz\n19\nBuzz\nFizz\n22\n23\nFizz\nBuzz\n26\nFizz\n28\n29\nFizzBuzz\n31\n32\nFizz\n34\nBuzz\nFizz\n37\n38\nFizz\nBuzz\n41\nFizz\n43\n44\nFizzBuzz\n46\n47\nFizz\n49\nBuzz\nFizz\n52\n53\nFizz\nBuzz\n56\nFizz\n58\n59\nFizzBuzz\n61\n62\nFizz\n64\nBuzz\nFizz\n67\n68\nFizz\nBuzz\n71\nFizz\n73\n74\nFizzBuzz\n76\n77\nFizz\n79\nBuzz\nFizz\n82\n83\nFizz\nBuzz\n86\nFizz\n88\n89\nFizzBuzz\n91\n92\nFizz\n94\nBuzz\nFizz\n97\n98\nFizz\nBuzz\n" Of course, having now written this I feel like I should retroactively fail my last interview. [1] https://gist.github.com/anonymous/7818f902a374a953b274 https://gist.github.com/anonymous/7818f902a374a953b274
- jevinskie 12y ago
  This code snippet really made my night. I never thought of using constexpr to write a FizzBuzz that compiles to one of the most "optimal" solutions that I have ever seen. Awesome!

eckzow 12y ago

By my reading that implementation was assembled by humans, not the optimizer. Although, there's certainly nothing magical that prevents the optimizer from generating such code. Here's something[1] I just threw together that (ab)uses constexpr to do just that. On my machine, building with: $ clang++ -std=c++14 fizzbuzz.cpp -O2 -S Gives code similar to: main: # @main .cfi_startproc # BB#0: pushq %rax .Ltmp0: .cfi_def_cfa_offset 16 movl $1, %edi movl $_ZL6output, %esi movl $413, %edx # imm = 0x19D callq write xorl %eax, %eax popq %rdx retq .Ltmp1: .size main, .Ltmp1-main .cfi_endproc .type _ZL6output,@object # @_ZL6output .section .rodata,"a",@progbits _ZL6output: .ascii "1\n2\nFizz\n4\nBuzz\nFizz\n7\n8\nFizz\nBuzz\n11\nFizz\n13\n14\nFizzBuzz\n16\n17\nFizz\n19\nBuzz\nFizz\n22\n23\nFizz\nBuzz\n26\nFizz\n28\n29\nFizzBuzz\n31\n32\nFizz\n34\nBuzz\nFizz\n37\n38\nFizz\nBuzz\n41\nFizz\n43\n44\nFizzBuzz\n46\n47\nFizz\n49\nBuzz\nFizz\n52\n53\nFizz\nBuzz\n56\nFizz\n58\n59\nFizzBuzz\n61\n62\nFizz\n64\nBuzz\nFizz\n67\n68\nFizz\nBuzz\n71\nFizz\n73\n74\nFizzBuzz\n76\n77\nFizz\n79\nBuzz\nFizz\n82\n83\nFizz\nBuzz\n86\nFizz\n88\n89\nFizzBuzz\n91\n92\nFizz\n94\nBuzz\nFizz\n97\n98\nFizz\nBuzz\n" Of course, having now written this I feel like I should retroactively fail my last interview. [1] https://gist.github.com/anonymous/7818f902a374a953b274 https://gist.github.com/anonymous/7818f902a374a953b274

jevinskie 12y ago
This code snippet really made my night. I never thought of using constexpr to write a FizzBuzz that compiles to one of the most "optimal" solutions that I have ever seen. Awesome!