libffi
A Portable Foreign Function Interface Library libffi-3.4.5 was released on February 15, 2024. You can download it from github here: https://github.com/libffi/libffi/releases/download/v3.4.5/libffi-3.4.5.tar.gz. libffi is Free Software. It has a very liberal license. What is libffi? Compilers for high level languages generate code that follows certain conventions. These conventions are necessary, i
4403 – strfry() gives skewed distributions
strfry() tries to shuffle its string using random swaps, but it uses the wrong strategy, and thus not all permutations are equally likely. The code doing the shuffling itself looks like this: len = strlen (string); for (i = 0; i < len; ++i) { int32_t j; char c; __random_r (&rdata, &j); j %= len; c = string[i]; string[i] = string[j]; string[j] = c; } In other words, for the string 'abc' j will alwa
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Tips for the Numerical Computation using GNU/Linux
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fast strlen and memchr by SSE2 (mitsunari@cybozu labs)
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ã¯ã˜ã‚ã¦ã®ã«ã(2008-04-13)
_ ã¹ã‚‹ã¬ãƒ¼ã„ ã¨ã‹çŸ¥ã‚‰ã‚“ã—。 ã¨ã—ã‹è¨€ãˆãªã„æ„Ÿã˜ã® SRM ã§ã‚ã£ãŸã€‚ ã‚㨠500 ã™ãã«è½ã¨ã›ã‚‹ã®è¦‹ã¤ã‘ãŸã‘ã©ä¸€çž¬è² ã‘ãŸã€‚ 250 è½ã¡ãŸã‚Šã—ãーã ã‚ã†ãªã€‚ (02:58) _ ã¾ã マジメã«åçœã™ã‚‹ã¨ 500ã§ã“ã‚Œã¯å…¬å¼æŽ¢ã•ã‚“ã¨ç„¡ç†ã 〠ã¨æ€ã£ã¦ããり始ã‚ã‚‹ã®ãŒé…ã™ãŽãŸãªã。 1000000007ã®ã‚±ã‚¿æ•°èªã¿é–“é•ãˆã¦ 10**8 ã®ã‚ªãƒ¼ãƒ€ãƒ¼ã ã¨æ€ã£ã¦ã€ ã“れ周期ã§è§£ã‘ã‚‹ã‚“ã˜ã‚ƒã€ã¨ã‹æ€ã£ã¦ã‚‹æ™‚é–“ãŒã¾ã‚‹ã§ãƒ ダã ã£ãŸã€‚ ナイーブã«è§£ã„ã¦ã¿ãŸã€‚é©å½“ã«èµ°ã‚‰ã›ã¦ã¿ã‚‹ã«ã‚„ã¯ã—é…ã„ ã©ã†ã—ãŸã‚‚ã‚“ã‹ã¨è€ƒãˆãŸ 周期ãŒã©ã†ã“ã†è€ƒãˆãŸ ããã‚ã†ã¨æ€ã£ã¦ããã£ãŸã‚‰æ•™ãˆã¦gooãŒå‡ºã¦ã㟠ã‚ã‚Œã“れ鉛ç†ã§é ‘å¼µã£ã¦ã¿ãŸã‘ã©æ³•å‰‡æ€§ã¨ã‹ãã¡ã‚“ã¨ã‚ã‹ã‚‰ãªã„㊠(?-?) MathWorld ã¨ã‹è¦‹ãŸã€‚よãã‚ã‹ã‚‰ã‚“㪠ãªã‚“ã‹ããã£ã¦å‡ºã¦ããŸã‚³ãƒ¼ãƒ‰ã¨ã‹è¦‹ãŸã‘ã©ã‚ˆãã‚ã‹ã‚‰ã‚“ãªã€‚写ã™ã®ã¯ä»ç¾©ã«åã™ã‚‹æ°—ãŒã™ã‚‹ã— ãã†ã maxi
strchr() ã§ã¯ã¾ã£ãŸè©± - bkブãƒã‚°
strchr() ã§ã¯ã¾ã£ãŸè©± 標準Cライブラリ㫠strchr() ã¨ã„ã†é–¢æ•°ãŒã‚ã‚Šã¾ã™ã€‚æ–‡å—列ã®å…ˆé ã‹ã‚‰æŒ‡å®šã—ãŸæ–‡å—を探ã™ã¨ã„ã†å˜ç´”ãªé–¢æ•°ãªã®ã§ã™ãŒã€å…ˆæ—¥ã€æ„外ãªä»•æ§˜ã‚’知りã¾ã—ãŸã€‚ 以下ã®ã‚³ãƒ¼ãƒ‰ã‚’見ã¦ã¿ã¾ã™ã€‚ if (strchr("+-*/", c)) { // c ã¯å››å‰‡æ¼”ç®—ã®è¨˜å·ã‹ãª? ... } ã“ã® if 文㯠c ㌠+ - * / ã®ã„ãšã‚Œã‹ã®å ´åˆã«æ¡ä»¶ãŒçœŸã¨ãªã‚Šã€ãƒ–ãƒãƒƒã‚¯ä¸ãŒå®Ÿè¡Œã•ã‚Œã¾ã™ã€‚…ã¨ã€æ€ã„ãã‚„ã€å®Ÿã¯æ¡ä»¶ãŒçœŸã«ãªã‚‹ã‚±ãƒ¼ã‚¹ãŒã‚‚ã†ã²ã¨ã¤ã‚ã‚Šã¾ã—ãŸã€‚c ㌠'\0' ã®å ´åˆã§ã™ã€‚ ã¾ã•ã‹ã¨æ€ã£ã¦æ‰‹å…ƒã® Linux ã® man を見るã¨ã€æ–‡å—列ã®çµ‚端ã®ãƒŠãƒ«æ–‡å— ('\0') ã®æ‰±ã„ã¯æ˜Žè¨˜ã•ã‚Œã¦ã„ã¾ã›ã‚“。 The strchr() function returns a pointer to the first occurrence of the character c i
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