Lua numbers in Tarantool

--- title: Lua numbers in Tarantool tags: Tarantool, Talk description: View the slide with "Slide Mode". slideOptions: theme: dark transition: none backgroundTransition: none width: 960 height: 540 margin: 0 ---  <style type="text/css"> * { tab-size: 4; } /* Resets & overrides */ .reveal dl { display: block; } .reveal pre { width: auto; box-shadow: none; } .reveal pre code { width: auto; max-height: initial; } .reveal blockquote { width: auto; } .reveal .slides .pdf-page { pointer-events: initial; } .reveal .slides { text-align: left; } /* Font style defs */ html, .reveal { font-family: "Open Sans", -apple-system, BlinkMacSystemFont, "Segoe UI", "Helvetica Neue", Helvetica, Roboto, Arial, sans-serif, "Apple Color Emoji", "Segoe UI Emoji", "Segoe UI Symbol"; } .reveal pre code { font-family: "PTM55F", "Monaco", monospace; } /* Color defs */ .reveal pre code { background: #2d2d2d; } /* Backgrounds */ .reveal .slide-background-content { background-color: #222; } .reveal .first .slide-background-content { background-color: #222; } .reveal section { background-color: #333; background-size: cover; background-image: url(https://slides.hb.bizmrg.com/tarantool/dark/page.png); } .reveal .slides section h1, .reveal .slides section h2, .reveal .slides section h3, .reveal .slides section h4, .reveal .slides section h5, .reveal .slides section h6{ background: rgba(0,0,0,0.25); } /* Font-sizes */ html { font-size: 32px; } .reveal { font-size: 1rem; } .reveal .slides section h1, .reveal .slides section h2, .reveal .slides section h3, .reveal .slides section h4, .reveal .slides section h5, .reveal .slides section h6{ font-size: 40px; } /* .reveal .slides section h1 { font-size: 42px } .reveal .slides section h2 { font-size: 40px } .reveal .slides section h3 { font-size: 38px } .reveal .slides section h4 { font-size: 36px } .reveal .slides section h5 { font-size: 34px } .reveal .slides section h6 { font-size: 32px } */ .reveal pre { font-size: 20px; line-height: 1.11; } .reveal pre code { font-size: inherit; } .reveal blockquote { font-size: 28px; } /* Paddings */ .reveal .slides section { width: 960px; height: 540px; } .reveal .slides > section, .reveal .slides > section > section { padding: 20px; } .reveal .slides > section > section { margin: 0 -20px; } .reveal .slides section h1, .reveal .slides section h2, .reveal .slides section h3, .reveal .slides section h4, .reveal .slides section h5, .reveal .slides section h6{ margin: -5px -20px 15px -20px; padding: 5px 20px; } .reveal dl { margin: 0; } .reveal dd { margin-bottom: 0.25em; } .reveal pre { margin: 10px -20px 20px -20px; padding: 0; } .reveal pre code { padding: 10px 20px; } .reveal blockquote { margin: 20px -20px 20px -20px; padding: 0; } .reveal blockquote > p { margin: 0 0 0 40px; padding: 0 0 0 5px; } /*** Helpers ***/ .reveal .slides section.center.present { display: grid !important; align-items: center; } .lr { display:grid; grid-gap: 0 50px; grid-template-columns: 1fr 1fr; } section.only-code pre { position: absolute; top: 10px; bottom: 10px; left: 0; right: 0; margin: 0; } section.only-code pre code { height: 100%; } /*** Modding ***/ .reveal .slides section .fragment.current-only { opacity: 1; visibility: visible; display: none; } .reveal .slides section .fragment.current-only.current-fragment { display: block; } .reveal .slides section li.fragment.current-only.current-fragment { display: list-item; } .reveal .slides section span.fragment.current-only.current-fragment { display: inline; } .reveal .slides section .fragment.visible-blurred { opacity: 1; visibility: visible; filter: blur(2px); } .reveal .slides section .fragment.visible-blurred.visible { filter: none; } .reveal .slides section .fragment.visible-blurred.visible.current-fragment { filter: none; text-shadow: 2px 2px #676767; } /*** Stylings ***/ dd { font-style: italic; } dd * { font-style: initial; } .reveal pre code { overflow: hidden; } .reveal blockquote > p { border-left: solid #333 10px; } .reveal .slides section { overflow: hidden; } section.first *[data-title] { position: absolute; left : 0; bottom: 0px; } .reveal .slides section.first h1 { margin-top: 25px; background: none; } .reveal .slides section.first h2 { background: none; } section.first .author { position: absolute; left : 20px; bottom: 20px; } </style>   # Lua numbers in Tarantool <address class="author"> Igor Munkin </address> --- # Problem #1 <pre><code class="tarantool hljs"> tarantool> 2^52 == 2^52 + 0.5 ––– - <result> ... </code></pre> ---- # Problem #1 <pre><code class="tarantool hljs"> tarantool> 2^52 == 2^52 + 0.5 ––– - true ... </code></pre> ---- # Problem #1 <pre><code class="tarantool hljs"> tarantool> 2^52 == 2^52 + 0.5 ––– - true ... tarantool> 2^52 == 2^52 + 1 ––– - <result> ... </code></pre> ---- # Problem #1 <pre><code class="tarantool hljs"> tarantool> 2^52 == 2^52 + 0.5 ––– - true ... tarantool> 2^52 == 2^52 + 1 ––– - false ... </code></pre> ---- # Problem #1 <pre><code class="tarantool hljs"> tarantool> 2^52 == 2^52 + 0.5 ––– - true ... tarantool> 2^52 == 2^52 + 1 ––– - false ... tarantool> 2^53 == 2^53 + 1 ––– - <result> ... </code></pre> ---- # Problem #1 <pre><code class="tarantool hljs"> tarantool> 2^52 == 2^52 + 0.5 ––– - true ... tarantool> 2^52 == 2^52 + 1 ––– - false ... tarantool> 2^53 == 2^53 + 1 ––– - true ... </code></pre> ---- # Problem #1 <pre><code class="tarantool hljs"> tarantool> 2^52 == 2^52 + 0.5 ––– - true ... tarantool> 2^52 == 2^52 + 1 ––– - false ... tarantool> 2^53 == 2^53 + 1 ––– - true ... tarantool> 2^53 == 2^53 + 2 ––– - <result> ... </code></pre> ---- # Problem #1 <pre><code class="tarantool hljs"> tarantool> 2^52 == 2^52 + 0.5 ––– - true ... tarantool> 2^52 == 2^52 + 1 ––– - false ... tarantool> 2^53 == 2^53 + 1 ––– - true ... tarantool> 2^53 == 2^53 + 2 ––– - false ... </code></pre> --- # Effect #1.1 <pre><code class="tarantool hljs"> tarantool> box.cfg{} <snip> box.space.s:create_index('i') ––– - <snip> ... </code></pre> ---- # Effect #1.1 <pre><code class="tarantool hljs"> tarantool> box.cfg{} <snip> box.space.s:create_index('i') ––– - <snip> ... tarantool> box.space.s:insert({2^53}) ––– - <result> ... </code></pre> ---- # Effect #1.1 <pre><code class="tarantool hljs"> tarantool> box.cfg{} <snip> box.space.s:create_index('i') ––– - <snip> ... tarantool> box.space.s:insert({2^53}) ––– - [9007199254740992] ... </code></pre> ---- # Effect #1.1 <pre><code class="tarantool hljs"> tarantool> box.cfg{} <snip> box.space.s:create_index('i') ––– - <snip> ... tarantool> box.space.s:insert({2^53}) ––– - [9007199254740992] ... tarantool> box.space.s:insert({2^53 + 1}) ––– - <result> ... </code></pre> ---- # Effect #1.1 <pre><code class="tarantool hljs"> tarantool> box.cfg{} <snip> box.space.s:create_index('i') ––– - <snip> ... tarantool> box.space.s:insert({2^53}) ––– - [9007199254740992] ... tarantool> box.space.s:insert({2^53 + 1}) ––– - error: Duplicate key exists in unique index 'i' in space 's' ... </code></pre> --- # Effect #1.2 <pre><code class="tarantool hljs"> tarantool> box.space.s:select({2^53}) ––– - <result> ... </code></pre> ---- # Effect #1.2 <pre><code class="tarantool hljs"> tarantool> box.space.s:select({2^53}) ––– - [9007199254740992] ... </code></pre> ---- # Effect #1.2 <pre><code class="tarantool hljs"> tarantool> box.space.s:select({2^53}) ––– - [9007199254740992] ... tarantool> box.space.s:select({2^53 + 1}) ––– - <result> ... </code></pre> ---- # Effect #1.2 <pre><code class="tarantool hljs"> tarantool> box.space.s:select({2^53}) ––– - [9007199254740992] ... tarantool> box.space.s:select({2^53 + 1}) ––– - [9007199254740992] ... </code></pre> --- # WAT #1 <pre><code class="tarantool hljs"> tarantool> type(box.space.s:select({2^53})[1]) ––– - <result> ... </code></pre> ---- # WAT #1 <pre><code class="tarantool hljs"> tarantool> type(box.space.s:select({2^53})[1]) ––– - cdata ... </code></pre> ---- # WAT #1 <div align="center"> <img src=https://media1.tenor.com/images/d3733ebb0b001e1baac25db96723f478/tenor.gif> </div> --- # Workaround #1 <pre><code class="tarantool hljs"> tarantool> 9007199254740992ULL ––– - <result> ... </code></pre> ---- # Workaround #1 <pre><code class="tarantool hljs"> tarantool> 9007199254740992ULL ––– - 9007199254740992 ... </code></pre> ---- # Workaround #1 <pre><code class="tarantool hljs"> tarantool> 9007199254740992ULL ––– - 9007199254740992 ... tarantool> type(9007199254740992ULL) ––– - <result> ... </code></pre> ---- # Workaround #1 <pre><code class="tarantool hljs"> tarantool> 9007199254740992ULL ––– - 9007199254740992 ... tarantool> type(9007199254740992ULL) ––– - cdata ... </code></pre> ---- # Workaround #1 <pre><code class="tarantool hljs"> tarantool> 9007199254740992ULL ––– - 9007199254740992 ... tarantool> type(9007199254740992ULL) ––– - cdata ... tarantool> 9007199254740992ULL + 1 ––– - <result> ... </code></pre> ---- # Workaround #1 <pre><code class="tarantool hljs"> tarantool> 9007199254740992ULL ––– - 9007199254740992 ... tarantool> type(9007199254740992ULL) ––– - cdata ... tarantool> 9007199254740992ULL + 1 ––– - 9007199254740993 ... </code></pre> ---- # Workaround #1 <pre><code class="tarantool hljs"> tarantool> 9007199254740992ULL + 1 ––– - 9007199254740993 ... tarantool> 9007199254740992ULL == 9007199254740992ULL + 1 ––– - <result> ... </code></pre> ---- # Workaround #1 <pre><code class="tarantool hljs"> tarantool> 9007199254740992ULL + 1 ––– - 9007199254740993 ... tarantool> 9007199254740992ULL == 9007199254740992ULL + 1 ––– - false ... </code></pre> ---- # Workaround #1 <pre><code class="tarantool hljs"> tarantool> 9007199254740992ULL + 1 ––– - 9007199254740993 ... tarantool> 9007199254740992ULL == 9007199254740992ULL + 1 ––– - false ... tarantool> 9007199254740992ULL == 9007199254740992ULL + 0.5 ––– - <result> ... </code></pre> ---- # Workaround #1 (?) <pre><code class="tarantool hljs"> tarantool> 9007199254740992ULL + 1 ––– - 9007199254740993 ... tarantool> 9007199254740992ULL == 9007199254740992ULL + 1 ––– - false ... tarantool> 9007199254740992ULL == 9007199254740992ULL + 0.5 ––– - true ... </code></pre> ---- # Workaround #1 (?) <pre><code class="tarantool hljs"> tarantool> 9007199254740992ULL == 9007199254740992ULL + 1 ––– - false ... tarantool> 9007199254740992ULL == 9007199254740992ULL + 0.5 ––– - true ... tarantool> 9007199254740992ULL + 0.5 ––– - 9007199254740992 ... </code></pre> --- # Problem #2 <pre><code class="tarantool hljs"> tarantool> 9007199254740992ULL < 9007199254740992ULL + 1 ––– - <result> ... </code></pre> ---- # Problem #2 <pre><code class="tarantool hljs"> tarantool> 9007199254740992ULL < 9007199254740992ULL + 1 ––– - true ... </code></pre> ---- # Problem #2 <pre><code class="tarantool hljs"> tarantool> 9007199254740992ULL < 9007199254740992ULL + 1 ––– - true ... tarantool> 9007199254740992ULL < -1 ––– - <result> ... </code></pre> ---- # Problem #2 <pre><code class="tarantool hljs"> tarantool> 9007199254740992ULL < 9007199254740992ULL + 1 ––– - true ... tarantool> 9007199254740992ULL < -1 ––– - true ... </code></pre> --- # Effect #2 <pre><code class="tarantool hljs"> tarantool> box.cfg{listen = 3313} <snip> c = nb.connect(box.cfg.listen) <snip> ––– ... </code></pre> ---- # Effect #2 <pre><code class="tarantool hljs"> tarantool> box.cfg{listen = 3313} <snip> c = nb.connect(box.cfg.listen) <snip> ––– ... tarantool> t = {} for _ = 1, 10 do > table.insert(t, > c:execute('SELECT random()').rows[1] > :totable()[1] > ) > end ––– ... </code></pre> ---- # Effect #2 <pre><code class="tarantool hljs"> tarantool> box.cfg{listen = 3313} <snip> c = nb.connect(box.cfg.listen) <snip> ––– ... tarantool> t = {} for _ = 1, 10 do > table.insert(t, > c:execute('SELECT random()').rows[1] > :totable()[1] > ) > end ––– ... tarantool> table.sort(t) ––– ... </code></pre> ---- # Effect #2 <pre><code class="tarantool hljs"> tarantool> t ––– - <result> ... </code></pre> ---- # Effect #2 <pre><code class="tarantool hljs"> tarantool> t ––– - - 1064442337705904389 - 5430535088656468933 - 8084626668617668138 - -7957167126669429942 - -6755436305203424895 - -6476727283901405634 - -5944830508420504980 - -2428743323307643782 - -1162597621816885600 - -108704732427766924 ... </code></pre> --- # Long story short * Native Lua numeric type * Lack of precision for several groups of numbers * FFI cdata numeric types * 64-bit integer promotion and cast rules according to C standard **Odd arithmetics for both existing numeric types** --- # Bonus tracks * [cdata double type arithmetics](https://blog.imun.cloud/Oh-Mike-Pall-1/) * [math.huge — huge or not?](https://blog.imun.cloud/Oh-Mike-Pall-2/)

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