memory

C/C++ performance of static arrays vs dynamic arrays

由 泪湿孤枕 提交于 2020-05-09 18:00:24
问题 When performance is essential to an application, should consideration be given whether to declare an array on the stack vs the heap? Allow me to outline why this question has come to mind. Since arrays in C/C++ are not objects and decay to pointers, the compiler uses the provided index to perform pointer arithmetic to access elements. My understanding is that this procedure differs from a statically declared array to a dynamically declared array when going past the first dimension. If I were

C/C++ performance of static arrays vs dynamic arrays

由 ﹥＞﹥吖頭↗ 提交于 2020-05-09 18:00:06
问题 When performance is essential to an application, should consideration be given whether to declare an array on the stack vs the heap? Allow me to outline why this question has come to mind. Since arrays in C/C++ are not objects and decay to pointers, the compiler uses the provided index to perform pointer arithmetic to access elements. My understanding is that this procedure differs from a statically declared array to a dynamically declared array when going past the first dimension. If I were

增加堆内存的大小

由 若如初见. 提交于 2020-05-03 21:51:59
增加堆内存的大小 - 提防眼镜蛇效应 原文: http://plumbr.eu/blog/increasing-heap-size-beware-of-the-cobra-effect "眼镜蛇效应"起源于当时英国统治印度殖民地的轶事。英国政府关心一些有毒的眼镜蛇.所以政府对每条死蛇提供奖励.最初这个方案很成功为了奖励大量的毒蛇被杀死.然而最终印度人为了收入开始养殖眼镜蛇. 当意识到奖励取消了,养殖眼镜蛇和野生眼镜蛇成倍增加了. 明显的这个问题解决方案使这个情况更糟了. 如何调整Java堆内存的大小就像殖民地印度和毒蛇的关系.多包涵，我会引导你通过这个比喻用一个故事从现实生活中作为参考。 你已经创建了一个强大的程序. 如此强大使程序变的真正的流利和有巨大的流量,新的服务开始添加到你的程序中.通过挖掘你决定的性能指标,你程序的可用堆内存将不久成为瓶颈. 因此你部署了是原来6倍堆内存的基础设施. 你测试你的程序验证它可以工作.你部署它到新的硬件上.但是立即开始抱怨下面的问题 - 你的程序变的比以前2GB堆内存时响应要慢. 你的一些用户面临着分等待你的程序的响应延迟几分钟. 发生了什么? 可以有很多原因.不过,让我们关注最有可能发生的地方 - 堆内存大小的改变.这里有几种不好的效果像扩展缓存的预热时间,碎片问题等.但是从症状上来看你最有可能面临的是full GC期间的延迟问题.

Shell simulation using lists

由 十年热恋 提交于 2020-04-18 05:43:13
问题 Now i'm learning C and I have a problem with memory alocation, atleast this I understand from my code error. Code #ifndef __FILE_H__ #define __FILE_H__ #include <stdlib.h> #include <stdio.h> #include <string.h> typedef struct Files Files; typedef struct DirList DirList; typedef struct NodeFile NodeFile; typedef struct NodeDir NodeDir; typedef struct Directory { // The name of the directory char *name; // TODO: The list of files of the current directory Files *files; // TODO: The list of dirs

C++ Program Not Relying on Virtual Memory

由 孤街浪徒 提交于 2020-04-17 22:20:26
问题 A homework assignment I am working on requires that we exhaust our main memory so that the program uses virtual memory so that we can observe and measure the slowdown. However, when I get to sufficiently large memory values, I segfault or crash. I need to exhaust main memory and use virtual memory simultaneously and I was under the impression that windows (or other operating systems) would just take care of this, at least that is how it has been portrayed to me. The program I am using to

Android cache affecting value of variable?

由 戏子无情 提交于 2020-04-17 20:29:03
问题 I'm using the code below within an Android app. In some phones, the code works correctly as expected. In others, a variable changes its value unexpectedly. Example of LogCat from some tests: 03-27 13:38:59.628 17735-17735/? I/System.out: my_var=1.0 03-27 13:38:59.651 17735-17740/? I/zygote: Do partial code cache collection, code=448KB, data=496KB 03-27 13:38:59.652 17735-17740/? I/zygote: After code cache collection, code=446KB, data=495KB Increasing code cache capacity to 2MB 03-27 13:38:59

Android cache affecting value of variable?

由 别等时光非礼了梦想. 提交于 2020-04-17 20:28:13
问题 I'm using the code below within an Android app. In some phones, the code works correctly as expected. In others, a variable changes its value unexpectedly. Example of LogCat from some tests: 03-27 13:38:59.628 17735-17735/? I/System.out: my_var=1.0 03-27 13:38:59.651 17735-17740/? I/zygote: Do partial code cache collection, code=448KB, data=496KB 03-27 13:38:59.652 17735-17740/? I/zygote: After code cache collection, code=446KB, data=495KB Increasing code cache capacity to 2MB 03-27 13:38:59

Wasm-bindgen: access wasm instance's memory buffer (from JS)

由 ≯℡__Kan透↙ 提交于 2020-04-16 06:07:20
问题 According to this github comment, I can re-create an Uint8ClampedArray or Uint8Array returned from Rust/wasm by accessing the memory of the wasm instance directly: const textureRaw = new Uint8ClampedArray(memory.buffer, texture.offset(), texture.size()); The thing is, the js files generated by wasm-bindgen already instantiate a wasm instance, and I'd want to access the memory of this particular instance but it doesn't seem to be exported: // XXXXX_bg.js const path = require('path').join(_

How to read from pointer address in Python?

由 懵懂的女人 提交于 2020-04-16 02:52:09
问题 I want to read in a Python script a number of bytes starting from a specific address. E.g., I want to read 40000 bytes starting from 0x561124456. The pointer is given from a C# app. I want to use this method to pass data between the app and script. I've used a TCP socket via localhost, but I want to try this method also. How can I do this? 回答1: If you really want to, enjoy: import ctypes g = (ctypes.c_char*40000).from_address(0x561124456) Looks like segfault fun. There are good socket

How can I merge these many csv files (around 130,000) using PySpark into one large dataset efficiently?

由 时间秒杀一切 提交于 2020-04-14 21:01:49
问题 I posted this question earlier and got some advice to use PySpark instead. How can I merge this large dataset into one large dataframe efficiently? The following zip file (https://fred.stlouisfed.org/categories/32263/downloaddata/INTRNTL_csv_2.zip) contains a folder called data with around 130,000 of csv files. I want to merge all of them into one single dataframe. I have 16gb of RAM and I keep running out of RAM when I hit the first few hundred files. The files' total size is only about 300
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