4 ms·

This doesn't add up. I started programming in late 80-ies, I've learnt Forth, C, WinAPI (I started seriously developing Windows programs with 2.0! Gosh, how old

by kika 13y ago

This doesn't add up. I started programming in late 80-ies, I've learnt Forth, C, WinAPI (I started seriously developing Windows programs with 2.0! Gosh, how old I am...), then moved to the brighter side, learnt C++, LISP, I used ksh and vi (never was smart enough to master Emacs), used sccs and then rcs, wrote my own implementation of TCP, did some embedded work in C and asm, etc, etc etc. Given that list, what would you consider obsolete now? It's been 2 decades, not 1, mind you. Asm? Well, the last time I touched this sword for a reason was 2005 and it was SSE assembler, something that compilers were not able to generate efficiently then (and to the large extent still not able).

Luyt 13y ago
Yeah, like very quick lowercasing of blocks of ASCII text, 8 characters at a time: char *strlwrmmx(char *buffer,int len=-1) { if (len==-1) len=strlen(buffer); unsigned __int64 a=0x4040404040404040; // 0x40='A'-1 unsigned __int64 z=0x5B5B5B5B5B5B5B5B; // 0x5B='Z'+1 unsigned __int64 c=0x2020202020202020; // conversion offset for lowercase->uppercase asm { mov edi,buffer mov ecx,len convblock: cmp ecx,8 jl rest movq mm4,c // Eight copies of conversion value movq mm2,a // Put eight "A" characters in mm2 movq mm3,z // Put eight "Z" characters in mm3 movq mm0,[edi] // Get next eight characters of our string movq mm1,mm0 // We need two copies pcmpgtb mm1,mm2 // Generate 1's in MM1 everywhere chars >= 'A' pcmpgtb mm3,mm0 // Generate 1's in MM3 everywhere chars <= 'Z' pand mm1,mm3 // Generate 1's in MM1 when 'A'<=chars<='Z' pand mm1,mm4 // Generates $20 in each spot we have a l.c. char paddb mm0,mm1 // Convert uppercase chars to lowercase by adding $20 movq [edi],mm0 // Store back in buffer sub ecx,8 add edi,8 jmp convblock rest: // convert any left characters one by one cmp ecx,0 je done convchar: mov al,[edi] cmp al,'A' jb skip cmp al,'Z' ja skip add al,0x20 mov [edi],al skip: inc edi loop convchar done: } return buffer; }
- frozenport 13y ago
  Out of curiosity what kind of program were you writing that it was bottlenecked by a UTF8 lowercase conversion?
  - Luyt 13y ago
    A text indexer. It did case-insensitive searching, so I lowercased everything (both source text and search terms), allowing me to use a quicker substring search (i.e., no need to compare characters with case insensitivity). The indexer had to chew huge amounts of text, so the quicker the lowercasing, the better.

by kika 13y ago

Luyt 13y ago

Yeah, like very quick lowercasing of blocks of ASCII text, 8 characters at a time: char *strlwrmmx(char *buffer,int len=-1) { if (len==-1) len=strlen(buffer); unsigned __int64 a=0x4040404040404040; // 0x40='A'-1 unsigned __int64 z=0x5B5B5B5B5B5B5B5B; // 0x5B='Z'+1 unsigned __int64 c=0x2020202020202020; // conversion offset for lowercase->uppercase asm { mov edi,buffer mov ecx,len convblock: cmp ecx,8 jl rest movq mm4,c // Eight copies of conversion value movq mm2,a // Put eight "A" characters in mm2 movq mm3,z // Put eight "Z" characters in mm3 movq mm0,[edi] // Get next eight characters of our string movq mm1,mm0 // We need two copies pcmpgtb mm1,mm2 // Generate 1's in MM1 everywhere chars >= 'A' pcmpgtb mm3,mm0 // Generate 1's in MM3 everywhere chars <= 'Z' pand mm1,mm3 // Generate 1's in MM1 when 'A'<=chars<='Z' pand mm1,mm4 // Generates $20 in each spot we have a l.c. char paddb mm0,mm1 // Convert uppercase chars to lowercase by adding $20 movq [edi],mm0 // Store back in buffer sub ecx,8 add edi,8 jmp convblock rest: // convert any left characters one by one cmp ecx,0 je done convchar: mov al,[edi] cmp al,'A' jb skip cmp al,'Z' ja skip add al,0x20 mov [edi],al skip: inc edi loop convchar done: } return buffer; }

frozenport 13y ago
Out of curiosity what kind of program were you writing that it was bottlenecked by a UTF8 lowercase conversion?
- Luyt 13y ago
  A text indexer. It did case-insensitive searching, so I lowercased everything (both source text and search terms), allowing me to use a quicker substring search (i.e., no need to compare characters with case insensitivity). The indexer had to chew huge amounts of text, so the quicker the lowercasing, the better.