工程

围绕 Robin Hood Hashing、探测距离和存储布局，拆解 ska::flat_hash_map 的实现思路。

从最小复现、指令集与 ABI 差异入手，定位旧版 GCC 环境中的 AVX2 崩溃问题。

继续把 k8s 用于模型转换和部署的自动化流程，然后发现之前安装 k8s 的文档不 work 了…… 时间是 2020 年 5 月 7 日，当前最新的 k8s 版本是 v1.18.2。 报错如下： 详细代码 1 2 3<2kzzqw6rsjid0 --discovery-token-ca-cert-hash sha256:c6c72bdc96c0ff4d59559ff915eee61ba7ac5e8b93c0b2f9e11e813412387ec2 --v=5 4W0507 15:45:12.608784 4768 join.go:346] [preflight] WARNING: JoinControlPane.controlPlane settings will be ignored when control-plane flag is not set. 5I0507 15:45:12.608822 4768 join.go:371] [preflight] found NodeName empty; using OS hostname as NodeName 6I0507 15:45:12.608853 4768 initconfiguration.go:103] detected and using CRI socket: /var/run/dockershim.sock 7[preflight] Running pre-flight checks 8I0507 15:45:12.608902 4768 preflight.go:90] [preflight] Running general checks 9I0507 15:45:12.608933 4768 checks.go:249] validating the existence and emptiness of directory /etc/kubernetes/manifests 10I0507 15:45:12.608966 4768 checks.go:286] validating the existence of file /etc/kubernetes/kubelet.conf 11I0507 15:45:12.608975 4768 checks.go:286] validating the existence of file /etc/kubernetes/bootstrap-kubelet.conf 12I0507 15:45:12.608985 4768 checks.go:102] validating the container runtime 13I0507 15:45:12.685381 4768 checks.go:128] validating if the service is enabled and active 14 [WARNING IsDockerSystemdCheck]: detected "cgroupfs" as the Docker cgroup driver. The recommended driver is "systemd". Please follow the guide at https://kubernetes.io/docs/setup/cri/ 15I0507 15:45:12.765669 4768 checks.go:335] validating the contents of file /proc/sys/net/bridge/bridge-nf-call-iptables 16I0507 15:45:12.765720 4768 checks.go:335] validating the contents of file /proc/sys/net/ipv4/ip_forward 17I0507 15:45:12.765752 4768 checks.go:649] validating whether swap is enabled or not 18I0507 15:45:12.765780 4768 checks.go:376] validating the presence of executable conntrack 19I0507 15:45:12.765804 4768 checks.go:376] validating the presence of executable ip 20I0507 15:45:12.765826 4768 checks.go:376] validating the presence of executable iptables 21I0507 15:45:12.765844 4768 checks.go:376] validating the presence of executable mount 22I0507 15:45:12.765864 4768 checks.go:376] validating the presence of executable nsenter 23I0507 15:45:12.765882 4768 checks.go:376] validating the presence of executable ebtables 24I0507 15:45:12.765902 4768 checks.go:376] validating the presence of executable ethtool 25I0507 15:45:12.765920 4768 checks.go:376] validating the presence of executable socat 26I0507 15:45:12.765935 4768 checks.go:376] validating the presence of executable tc 27I0507 15:45:12.765953 4768 checks.go:376] validating the presence of executable touch 28I0507 15:45:12.765973 4768 checks.go:520] running all checks 29I0507 15:45:12.844881 4768 checks.go:406] checking whether the given node name is reachable using net.LookupHost 30I0507 15:45:12.845030 4768 checks.go:618] validating kubelet version 31I0507 15:45:12.888056 4768 checks.go:128] validating if the service is enabled and active 32I0507 15:45:12.893254 4768 checks.go:201] validating availability of port 10250 33I0507 15:45:12.893373 4768 checks.go:286] validating the existence of file /etc/kubernetes/pki/ca.crt 34I0507 15:45:12.893388 4768 checks.go:432] validating if the connectivity type is via proxy or direct 35I0507 15:45:12.893414 4768 join.go:441] [preflight] Discovering cluster-info 36I0507 15:45:12.893440 4768 token.go:78] [discovery] Created cluster-info discovery client, requesting info from "172.20.52.117:6443" 37I0507 15:45:13.033539 4768 token.go:116] [discovery] Requesting info from "172.20.52.117:6443" again to validate TLS against the pinned public key 38I0507 15:45:13.172634 4768 token.go:133] [discovery] Cluster info signature and contents are valid and TLS certificate validates against pinned roots, will use API Server "172.20.52.117:6443" 39I0507 15:45:13.172653 4768 discovery.go:51] [discovery] Using provided TLSBootstrapToken as authentication credentials for the join process 40I0507 15:45:13.172660 4768 join.go:455] [preflight] Fetching init configuration 41I0507 15:45:13.172669 4768 join.go:493] [preflight] Retrieving KubeConfig objects 42[preflight] Reading configuration from the cluster... 43[preflight] FYI: You can look at this config file with 'kubectl -n kube-system get cm kubeadm-config -oyaml' 44I0507 15:45:13.541858 4768 interface.go:400] Looking for default routes with IPv4 addresses 45I0507 15:45:13.541871 4768 interface.go:405] Default route transits interface "eth0" 46I0507 15:45:13.541941 4768 interface.go:208] Interface eth0 is up 47I0507 15:45:13.541978 4768 interface.go:256] Interface "eth0" has 2 addresses :[10.198.21.97/22 fe80::f816:3eff:fe5e:88f1/64]. 48I0507 15:45:13.541998 4768 interface.go:223] Checking addr 10.198.21.97/22. 49I0507 15:45:13.542008 4768 interface.go:230] IP found 10.198.21.97 50I0507 15:45:13.542016 4768 interface.go:262] Found valid IPv4 address 10.198.21.97 for interface "eth0". 51I0507 15:45:13.542023 4768 interface.go:411] Found active IP 10.198.21.97 52I0507 15:45:13.542057 4768 preflight.go:101] [preflight] Running configuration dependant checks 53I0507 15:45:13.542072 4768 controlplaneprepare.go:211] [download-certs] Skipping certs download 54I0507 15:45:13.542080 4768 kubelet.go:111] [kubelet-start] writing bootstrap kubelet config file at /etc/kubernetes/bootstrap-kubelet.conf 55I0507 15:45:13.542775 4768 kubelet.go:119] [kubelet-start] writing CA certificate at /etc/kubernetes/pki/ca.crt 56I0507 15:45:13.543283 4768 kubelet.go:145] [kubelet-start] Checking for an existing Node in the cluster with name "host-10-198-21-97" and status "Ready" 57nodes "host-10-198-21-97" is forbidden: User "system:bootstrap:0752yx" cannot get resource "nodes" in API group "" at the cluster scope 58cannot get Node "host-10-198-21-97" 59k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/join.runKubeletStartJoinPhase 60 /workspace/anago-v1.18.2-beta.0.14+a78cd082e8c913/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/join/kubelet.go:148 61k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/workflow.(*Runner).Run.func1 62 /workspace/anago-v1.18.2-beta.0.14+a78cd082e8c913/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/workflow/runner.go:234 63k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/workflow.(*Runner).visitAll 64 /workspace/anago-v1.18.2-beta.0.14+a78cd082e8c913/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/workflow/runner.go:422 65k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/workflow.(*Runner).Run 66 /workspace/anago-v1.18.2-beta.0.14+a78cd082e8c913/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/workflow/runner.go:207 67k8s.io/kubernetes/cmd/kubeadm/app/cmd.NewCmdJoin.func1 68 /workspace/anago-v1.18.2-beta.0.14+a78cd082e8c913/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/cmd/kubeadm/app/cmd/join.go:170 69k8s.io/kubernetes/vendor/github.com/spf13/cobra.(*Command).execute 70 /workspace/anago-v1.18.2-beta.0.14+a78cd082e8c913/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/vendor/github.com/spf13/cobra/command.go:826 71k8s.io/kubernetes/vendor/github.com/spf13/cobra.(*Command).ExecuteC 72 /workspace/anago-v1.18.2-beta.0.14+a78cd082e8c913/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/vendor/github.com/spf13/cobra/command.go:914 73k8s.io/kubernetes/vendor/github.com/spf13/cobra.(*Command).Execute 74 /workspace/anago-v1.18.2-beta.0.14+a78cd082e8c913/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/vendor/github.com/spf13/cobra/command.go:864 75k8s.io/kubernetes/cmd/kubeadm/app.Run 76 /workspace/anago-v1.18.2-beta.0.14+a78cd082e8c913/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/cmd/kubeadm/app/kubeadm.go:50 77main.main 78 _output/dockerized/go/src/k8s.io/kubernetes/cmd/kubeadm/kubeadm.go:25 79runtime.main 80 /usr/local/go/src/runtime/proc.go:203 81runtime.goexit 82 /usr/local/go/src/runtime/asm_amd64.s:1357 83error execution phase kubelet-start 84k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/workflow.(*Runner).Run.func1 85 /workspace/anago-v1.18.2-beta.0.14+a78cd082e8c913/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/workflow/runner.go:235 86k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/workflow.(*Runner).visitAll 87 /workspace/anago-v1.18.2-beta.0.14+a78cd082e8c913/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/workflow/runner.go:422 88k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/workflow.(*Runner).Run 89 /workspace/anago-v1.18.2-beta.0.14+a78cd082e8c913/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/cmd/kubeadm/app/cmd/phases/workflow/runner.go:207 90k8s.io/kubernetes/cmd/kubeadm/app/cmd.NewCmdJoin.func1 91 /workspace/anago-v1.18.2-beta.0.14+a78cd082e8c913/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/cmd/kubeadm/app/cmd/join.go:170 92k8s.io/kubernetes/vendor/github.com/spf13/cobra.(*Command).execute 93 /workspace/anago-v1.18.2-beta.0.14+a78cd082e8c913/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/vendor/github.com/spf13/cobra/command.go:826 94k8s.io/kubernetes/vendor/github.com/spf13/cobra.(*Command).ExecuteC 95 /workspace/anago-v1.18.2-beta.0.14+a78cd082e8c913/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/vendor/github.com/spf13/cobra/command.go:914 96k8s.io/kubernetes/vendor/github.com/spf13/cobra.(*Command).Execute 97 /workspace/anago-v1.18.2-beta.0.14+a78cd082e8c913/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/vendor/github.com/spf13/cobra/command.go:864 98k8s.io/kubernetes/cmd/kubeadm/app.Run 99 /workspace/anago-v1.18.2-beta.0.14+a78cd082e8c913/src/k8s.io/kubernetes/_output/dockerized/go/src/k8s.io/kubernetes/cmd/kubeadm/app/kubeadm.go:50 100main.main 101 _output/dockerized/go/src/k8s.io/kubernetes/cmd/kubeadm/kubeadm.go:25 102runtime.main 103 /usr/local/go/src/runtime/proc.go:203 104runtime.goexit 105 /usr/local/go/src/runtime/asm_amd64.s:1357 看起来关键的报错在这一句

背景是要把某个 caffe model 转换成 tensorrt 的 INT8 模型，然后遇到如下报错： 1 2E0403 08:54:35.951987 5704 engine.h:62] engine.cpp (572) - Cuda Error in commonEmitTensor: 1 (invalid argument) 3E0403 08:54:35.952157 5704 engine.h:62] Failure while trying to emit debug blob. 4engine.cpp (572) - Cuda Error in commonEmitTensor: 1 (invalid argument) 5E0403 08:54:35.952235 5704 engine.h:62] cuda/caskConvolutionLayer.cpp (355) - Cuda Error in execute: 1 (invalid argument) 6E0403 08:54:35.952291 5704 engine.h:62] cuda/caskConvolutionLayer.cpp (355) - Cuda Error in execute: 1 (invalid argument) 7W0403 08:54:35.952324 5704 calibrator.cpp:45] [4, 3, 224, 224] 8F0403 08:54:35.992761 5704 tensor.h:149] Check failed: cudaMemcpy(raw_mutable_data(), b.raw_data(), size_in_bytes, cudaMemcpyDefault) == cudaSuccess (700 vs. 0) 9*** Check failure stack trace: *** 10Aborted (core dumped) cuda error 700. 原来 cuda error 的错误号可以这么大。。

名词说明 # CUDA. 一般来说指的是CUDA SDK. 目前经常使用的是CUDA 8.0和CUDA 10.1两个版本. 8.0和10.1都是SDK的版本号. CUDNN. The NVIDIA CUDA® Deep Neural Network library (cuDNN). 是一个可以为神经网络提供GPU加速的库 compute capability. 是GPU的固有参数，可以理解为GPU的版本.越新的显卡该数值往往越高. tensorRT.NVIDIA TensorRT™ is an SDK for high-performance deep learning inference. 是一个深度学习推理库，旨在提供高性能的推理速度. plan file，也称为 engine plan. 是生成的tensorRT 模型文件. 兼容性说明 # Engine plan 的兼容性依赖于GPU的compute capability 和 TensorRT 版本， 不依赖于CUDA和CUDNN版本.

年中的时候接了离职的同事模型转换的锅，在不断地更新迭代的过程中，发现了一些痛点。 发现k8s能够解决一部分痛点，因此来分享一下在这方面的探索。 什么是模型转换 # 简单来说，深度学习模型的流程分为training和inference两部分。训练时用的一般是pytorch等框架，这些框架训练出的model是没办法直接部署在各个硬件平台上做inference的。因此需要将使用训练框架得到的模型，转换为能够部署到各个硬件平台上的模型。这个过程就是模型转换。

概述 # YUV是一种图像编码方式，或者称为色彩空间,与RGB是同级的概念. YUV是三个分量，Y,U和V，其中： Y 表示明亮度(Luminance或Luma)，也就是灰度值， U,V表示色度，浓度（Chrominance、Chroma），可以简单理解成用来表示某个像素的颜色的量. YUV格式的特点是，在对照片或影片编码时，考虑到人类的感知能力，允许降低色度的带宽。 也就是说，YUV不像RGB那样要求三个独立的视频信号同时传输，所以用YUV方式传送占用极少的频宽。

Halide is a programming language designed to make it easier to write high-performance image and array processing code on modern machines. halide有两个特性比较吸引人。一个是对于各种平台架构的支持。 CPU architectures: X86, ARM, MIPS, Hexagon, PowerPC Operating systems: Linux, Windows, macOS, Android, iOS, Qualcomm QuRT GPU Compute APIs: CUDA, OpenCL, OpenGL, OpenGL Compute Shaders, Apple Metal, Microsoft Direct X 12 另一个是把计算什么和怎么计算(何时计算)分离开来。

迫于生计，最近要学习halide 先去学习/复习一下常见的编译优化技巧。 loop unrolling，也就是循环展开，顾名思义，就是把循环展开来写。 1normal loop: 2int x; 3 for (x = 0; x < 100; x++) 4 { 5 delete(x); 6 } 7 8after loop unrolling: 9int x; 10 for (x = 0; x < 100; x += 5 ) 11 { 12 delete(x); 13 delete(x + 1); 14 delete(x + 2); 15 delete(x + 3); 16 delete(x + 4); 17 } 循环展开是一种优化，可以手动实现也可以编译器自动实现。

起因： # 公司部署在 hk 的爬虫服务器突然挂掉了。后来发现只是在深圳办公区无法访问。排查后发现原因是 docker 的网络（包括 docker network 的 subnet 或者是某个容器的 ip）与该 host 在内网的 ip 段相同，导致冲突。

现象： # 使用docker compose 挂载 named volume 无效（且没有错误提示) 排查过程： # 一开始是没有使用docker-compose命令，直接使用docker run -v 命令，挂载两个绝对路径，没有问题。

在 medium 上看到一篇很赞的文章……无奈关键部分一律无法加载出来，挂了梯子也不行，很心塞。刚刚突然发现加载出来了，以防之后再次无法访问，所以搬运过来。 There are couple of articles on how to integrate Scrapy into a Django Application (or vice versa?). But most of them don’t cover a full complete example that includes triggering spiders from Django views. Since this is a web application, that must be our main goal.

lua 是一门轻量级的脚本语言，好像比较适合写游戏？我在 太阳神三国杀 中见过很多 lua 脚本。由于 splash 的渲染脚本需要用 lua 来写，因此来学习一波。 直接上语法，看到了 python 和 pascal 的影子 orz。 详细代码 1-- Two dashes start a one-line comment. 2 3--[[ 4 Adding two ['s and ]'s makes it a 5 multi-line comment. 6--]] 7 8---------------------------------------------------- 9-- 1. Variables and flow control. 10---------------------------------------------------- 11 12num = 42 -- All numbers are doubles. 13-- Don't freak out, 64-bit doubles have 52 bits for 14-- storing exact int values; machine precision is 15-- not a problem for ints that need < 52 bits. 16 17s = 'walternate' -- Immutable strings like Python. 18t = "double-quotes are also fine" 19u = [[ Double brackets 20 start and end 21 multi-line strings.]] 22t = nil -- Undefines t; Lua has garbage collection. 23 24-- Blocks are denoted with keywords like do/end: 25while num < 50 do 26 num = num + 1 -- No ++ or += type operators. 27end 28 29-- If clauses: 30if num > 40 then 31 print('over 40') 32elseif s ~= 'walternate' then -- ~= is not equals. 33 -- Equality check is == like Python; ok for strs. 34 io.write('not over 40\n') -- Defaults to stdout. 35else 36 -- Variables are global by default. 37 thisIsGlobal = 5 -- Camel case is common. 38 39 -- How to make a variable local: 40 local line = io.read() -- Reads next stdin line. 41 42 -- String concatenation uses the .. operator: 43 print('Winter is coming, ' .. line) 44end 45 46-- Undefined variables return nil. 47-- This is not an error: 48foo = anUnknownVariable -- Now foo = nil. 49 50aBoolValue = false 51 52-- Only nil and false are falsy; 0 and '' are true! 53if not aBoolValue then print('twas false') end 54 55-- 'or' and 'and' are short-circuited. 56-- This is similar to the a?b:c operator in C/js: 57ans = aBoolValue and 'yes' or 'no' --> 'no' 58 59karlSum = 0 60for i = 1, 100 do -- The range includes both ends. 61 karlSum = karlSum + i 62end 63 64-- Use "100, 1, -1" as the range to count down: 65fredSum = 0 66for j = 100, 1, -1 do fredSum = fredSum + j end 67 68-- In general, the range is begin, end[, step]. 69 70-- Another loop construct: 71repeat 72 print('the way of the future') 73 num = num - 1 74until num == 0 75 76 77---------------------------------------------------- 78-- 2. Functions. 79---------------------------------------------------- 80 81function fib(n) 82 if n < 2 then return 1 end 83 return fib(n - 2) + fib(n - 1) 84end 85 86-- Closures and anonymous functions are ok: 87function adder(x) 88 -- The returned function is created when adder is 89 -- called, and remembers the value of x: 90 return function (y) return x + y end 91end 92a1 = adder(9) 93a2 = adder(36) 94print(a1(16)) --> 25 95print(a2(64)) --> 100 96 97-- Returns, func calls, and assignments all work 98-- with lists that may be mismatched in length. 99-- Unmatched receivers are nil; 100-- unmatched senders are discarded. 101 102x, y, z = 1, 2, 3, 4 103-- Now x = 1, y = 2, z = 3, and 4 is thrown away. 104 105function bar(a, b, c) 106 print(a, b, c) 107 return 4, 8, 15, 16, 23, 42 108end 109 110x, y = bar('zaphod') --> prints "zaphod nil nil" 111-- Now x = 4, y = 8, values 15..42 are discarded. 112 113-- Functions are first-class, may be local/global. 114-- These are the same: 115function f(x) return x * x end 116f = function (x) return x * x end 117 118-- And so are these: 119local function g(x) return math.sin(x) end 120local g; g = function (x) return math.sin(x) end 121-- the 'local g' decl makes g-self-references ok. 122 123-- Trig funcs work in radians, by the way. 124 125-- Calls with one string param don't need parens: 126print 'hello' -- Works fine. 127 128 129---------------------------------------------------- 130-- 3. Tables. 131---------------------------------------------------- 132 133-- Tables = Lua's only compound data structure; 134-- they are associative arrays. 135-- Similar to php arrays or js objects, they are 136-- hash-lookup dicts that can also be used as lists. 137 138-- Using tables as dictionaries / maps: 139 140-- Dict literals have string keys by default: 141t = {key1 = 'value1', key2 = false} 142 143-- String keys can use js-like dot notation: 144print(t.key1) -- Prints 'value1'. 145t.newKey = {} -- Adds a new key/value pair. 146t.key2 = nil -- Removes key2 from the table. 147 148-- Literal notation for any (non-nil) value as key: 149u = {['@!#'] = 'qbert', [{}] = 1729, [6.28] = 'tau'} 150print(u[6.28]) -- prints "tau" 151 152-- Key matching is basically by value for numbers 153-- and strings, but by identity for tables. 154a = u['@!#'] -- Now a = 'qbert'. 155b = u[{}] -- We might expect 1729, but it's nil: 156-- b = nil since the lookup fails. It fails 157-- because the key we used is not the same object 158-- as the one used to store the original value. So 159-- strings & numbers are more portable keys. 160 161-- A one-table-param function call needs no parens: 162function h(x) print(x.key1) end 163h{key1 = 'Sonmi~451'} -- Prints 'Sonmi~451'. 164 165for key, val in pairs(u) do -- Table iteration. 166 print(key, val) 167end 168 169-- _G is a special table of all globals. 170print(_G['_G'] == _G) -- Prints 'true'. 171 172-- Using tables as lists / arrays: 173 174-- List literals implicitly set up int keys: 175v = {'value1', 'value2', 1.21, 'gigawatts'} 176for i = 1, #v do -- #v is the size of v for lists. 177 print(v[i]) -- Indices start at 1 !! SO CRAZY! 178end 179-- A 'list' is not a real type. v is just a table 180-- with consecutive integer keys, treated as a list. 181 182---------------------------------------------------- 183-- 3.1 Metatables and metamethods. 184---------------------------------------------------- 185 186-- A table can have a metatable that gives the table 187-- operator-overloadish behavior. Later we'll see 188-- how metatables support js-prototypey behavior. 189 190f1 = {a = 1, b = 2} -- Represents the fraction a/b. 191f2 = {a = 2, b = 3} 192 193-- This would fail: 194-- s = f1 + f2 195 196metafraction = {} 197function metafraction.__add(f1, f2) 198 sum = {} 199 sum.b = f1.b * f2.b 200 sum.a = f1.a * f2.b + f2.a * f1.b 201 return sum 202end 203 204setmetatable(f1, metafraction) 205setmetatable(f2, metafraction) 206 207s = f1 + f2 -- call __add(f1, f2) on f1's metatable 208 209-- f1, f2 have no key for their metatable, unlike 210-- prototypes in js, so you must retrieve it as in 211-- getmetatable(f1). The metatable is a normal table 212-- with keys that Lua knows about, like __add. 213 214-- But the next line fails since s has no metatable: 215-- t = s + s 216-- Class-like patterns given below would fix this. 217 218-- An __index on a metatable overloads dot lookups: 219defaultFavs = {animal = 'gru', food = 'donuts'} 220myFavs = {food = 'pizza'} 221setmetatable(myFavs, {__index = defaultFavs}) 222eatenBy = myFavs.animal -- works! thanks, metatable 223 224-- Direct table lookups that fail will retry using 225-- the metatable's __index value, and this recurses. 226 227-- An __index value can also be a function(tbl, key) 228-- for more customized lookups. 229 230-- Values of __index,add, .. are called metamethods. 231-- Full list. Here a is a table with the metamethod. 232 233-- __add(a, b) for a + b 234-- __sub(a, b) for a - b 235-- __mul(a, b) for a * b 236-- __div(a, b) for a / b 237-- __mod(a, b) for a % b 238-- __pow(a, b) for a ^ b 239-- __unm(a) for -a 240-- __concat(a, b) for a .. b 241-- __len(a) for #a 242-- __eq(a, b) for a == b 243-- __lt(a, b) for a < b 244-- __le(a, b) for a <= b 245-- __index(a, b) <fn or a table> for a.b 246-- __newindex(a, b, c) for a.b = c 247-- __call(a, ...) for a(...) 248 249---------------------------------------------------- 250-- 3.2 Class-like tables and inheritance. 251---------------------------------------------------- 252 253-- Classes aren't built in; there are different ways 254-- to make them using tables and metatables. 255 256-- Explanation for this example is below it. 257 258Dog = {} -- 1. 259 260function Dog:new() -- 2. 261 newObj = {sound = 'woof'} -- 3. 262 self.__index = self -- 4. 263 return setmetatable(newObj, self) -- 5. 264end 265 266function Dog:makeSound() -- 6. 267 print('I say ' .. self.sound) 268end 269 270mrDog = Dog:new() -- 7. 271mrDog:makeSound() -- 'I say woof' -- 8. 272 273-- 1. Dog acts like a class; it's really a table. 274-- 2. function tablename:fn(...) is the same as 275-- function tablename.fn(self, ...) 276-- The : just adds a first arg called self. 277-- Read 7 & 8 below for how self gets its value. 278-- 3. newObj will be an instance of class Dog. 279-- 4. self = the class being instantiated. Often 280-- self = Dog, but inheritance can change it. 281-- newObj gets self's functions when we set both 282-- newObj's metatable and self's __index to self. 283-- 5. Reminder: setmetatable returns its first arg. 284-- 6. The : works as in 2, but this time we expect 285-- self to be an instance instead of a class. 286-- 7. Same as Dog.new(Dog), so self = Dog in new(). 287-- 8. Same as mrDog.makeSound(mrDog); self = mrDog. 288 289---------------------------------------------------- 290 291-- Inheritance example: 292 293LoudDog = Dog:new() -- 1. 294 295function LoudDog:makeSound() 296 s = self.sound .. ' ' -- 2. 297 print(s .. s .. s) 298end 299 300seymour = LoudDog:new() -- 3. 301seymour:makeSound() -- 'woof woof woof' -- 4. 302 303-- 1. LoudDog gets Dog's methods and variables. 304-- 2. self has a 'sound' key from new(), see 3. 305-- 3. Same as LoudDog.new(LoudDog), and converted to 306-- Dog.new(LoudDog) as LoudDog has no 'new' key, 307-- but does have __index = Dog on its metatable. 308-- Result: seymour's metatable is LoudDog, and 309-- LoudDog.__index = LoudDog. So seymour.key will 310-- = seymour.key, LoudDog.key, Dog.key, whichever 311-- table is the first with the given key. 312-- 4. The 'makeSound' key is found in LoudDog; this 313-- is the same as LoudDog.makeSound(seymour). 314 315-- If needed, a subclass's new() is like the base's: 316function LoudDog:new() 317 newObj = {} 318 -- set up newObj 319 self.__index = self 320 return setmetatable(newObj, self) 321end 322 323---------------------------------------------------- 324-- 4. Modules. 325---------------------------------------------------- 326 327 328--[[ I'm commenting out this section so the rest of 329-- this script remains runnable. 330-- Suppose the file mod.lua looks like this: 331local M = {} 332 333local function sayMyName() 334 print('Hrunkner') 335end 336 337function M.sayHello() 338 print('Why hello there') 339 sayMyName() 340end 341 342return M 343 344-- Another file can use mod.lua's functionality: 345local mod = require('mod') -- Run the file mod.lua. 346 347-- require is the standard way to include modules. 348-- require acts like: (if not cached; see below) 349local mod = (function () 350 <contents of mod.lua> 351end)() 352-- It's like mod.lua is a function body, so that 353-- locals inside mod.lua are invisible outside it. 354 355-- This works because mod here = M in mod.lua: 356mod.sayHello() -- Says hello to Hrunkner. 357 358-- This is wrong; sayMyName only exists in mod.lua: 359mod.sayMyName() -- error 360 361-- require's return values are cached so a file is 362-- run at most once, even when require'd many times. 363 364-- Suppose mod2.lua contains "print('Hi!')". 365local a = require('mod2') -- Prints Hi! 366local b = require('mod2') -- Doesn't print; a=b. 367 368-- dofile is like require without caching: 369dofile('mod2.lua') --> Hi! 370dofile('mod2.lua') --> Hi! (runs it again) 371 372-- loadfile loads a lua file but doesn't run it yet. 373f = loadfile('mod2.lua') -- Call f() to run it. 374 375-- loadstring is loadfile for strings. 376g = loadstring('print(343)') -- Returns a function. 377g() -- Prints out 343; nothing printed before now. 378 379--]] 380 381---------------------------------------------------- 382-- 5. References. 383---------------------------------------------------- 384 385--[[ 386 387I was excited to learn Lua so I could make games 388with the Löve 2D game engine. That's the why. 389 390I started with BlackBulletIV's Lua for programmers. 391Next I read the official Programming in Lua book. 392That's the how. 393 394It might be helpful to check out the Lua short 395reference on lua-users.org. 396 397The main topics not covered are standard libraries: 398 * string library 399 * table library 400 * math library 401 * io library 402 * os library 403 404By the way, this entire file is valid Lua; save it 405as learn.lua and run it with "lua learn.lua" ! 406 407This was first written for tylerneylon.com. It's 408also available as a github gist. Tutorials for other 409languages, in the same style as this one, are here: 410 411http://learnxinyminutes.com/ 412 413Have fun with Lua! 414 415--]]

先放资料，可能比较侧重于go在系统调用方面的内容. 这里不会记录详细的go的语法，只会记录学习的过程，踩到的坑，以及其他我认为值得记录的内容. go的switch语句终于是人类思维的语句了…匹配中了不需要加break..

再次迫于生计。。。 参考了面向新人的 Python 爬虫学习资料 大致的学习路线为： 一： 简单的定向脚本爬虫（ request — bs4 — re ） 二： 大型框架式爬虫（ Scrapy 框架为主） 三：浏览器模拟爬虫 （ Mechanize 模拟 和 Selenium 模拟） 有 Python 基础和一点 html 基础的话，貌似上手是 0 难度的。

最近的项目需要java和python之间的进程通信，想到了之前使用过的 grpc。 参考官方quickstart JDK: version 7 or higher 看起来只依赖jdk，美滋滋 然后按照文档执行 ./gradlew installDist 报错： 1Task :grpc-compiler:compileJava_pluginExecutableJava_pluginCpp FAILED 2 3FAILURE: Build failed with an exception. 4 5* What went wrong: 6Execution failed for task ':grpc-compiler:compileJava_pluginExecutableJava_pluginCpp'. 7> No tool chain is available to build for platform 'x86_64': 8 - Tool chain 'visualCpp' (Visual Studio): Visual Studio is not available on this operating system. 9 - Tool chain 'gcc' (GNU GCC): Could not determine GCC metadata: could not find vendor in output of /usr/local/gcc-4.9.4/bin/gcc. 10 - Tool chain 'clang' (Clang): Could not find C compiler 'clang' in system path. 11 12* Try: 13Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output. Run with --scan to get full insights. 14 15* Get more help at https://help.gradle.org 16 17BUILD FAILED in 3m 47s 18 19~ 看起来是 gcc 或者 clang 的问题… 先装个 clang 再说，可能 clang 太常用了，所以文档没有提到，这下一定可以了。

迫于生计，又要从零开始学习spring. 在这篇文章之前，对java的基础是2015年写过一个java大作业，对spring是一无所知。 为了学习spring，我按顺序做了以下事情：

真是个不明觉厉的术语…其实是个特别简单的概念orz 用白话讲，如果一个class A中用到了class B的实例，那么class B的实例就是class A的依赖，如果不是在class A中定义class B的实例，而是通过某个接口，将class B的实例传入class A，就叫依赖注入。

系统为ubuntu 14.04 迫于特别想定时换壁纸，查了下解决方案。 发现只要删除掉/usr目录下所有的’.pyc’文件就可以 命令为：sudo find /usr -name ‘*.pyc’ -delete

把 std::async、std::packaged_task、std::promise 三个放在一起来说，是因为它们都可以返回一个 std::future 对象。简单来说，当某个线程需要等待一个特定的一次性事件（one-off event），它可以用一个 “future” 来表示这个事件。