The procedure is quite the same as for gcc 4.8 as you can see in my older post Installing gcc, g++ and gfortran 4.8 from source Read the manual. Download, unpack, switch dir, download, unpack, link. $ wget ftp://ftp.gwdg.de/pub/misc/gcc/snapshots/LATEST-8/gcc-8-20190118.tar.xz $ xz -d gcc-8-20190118.tar.xz $ tar xf gcc-8-20190118.tar $ gcc-8-20190118/ $ wget ftp://ftp.gmplib.org/pub/gmp-6.1.2/gmp-6.1.2.tar.bz2 $ tar xjf […]
24.01.2019
Installing gcc, g++ and gfortran 8 from source
Comments Off on Installing gcc, g++ and gfortran 8 from source
20.04.2018
C++ Guns: Levenshtein-Distanz - Teil 1
Die Levenshtein-Distanz (auch Editierdistanz) zwischen zwei Zeichenketten ist die minimale Anzahl von Einfüge-, Lösch- und Ersetz-Operationen, um die erste Zeichenkette in die zweite umzuwandeln. Die Laufzeit Komplexität liegt bei quadratisch. Wie schnell ist das? Getestet werden 1000 Sequencen mit 200 Zeichen Länge. Die erste Implementierung von Wikipedia lasse ich im Debug Modus laufen und komme […]
Comments Off on C++ Guns: Levenshtein-Distanz - Teil 1
11.05.2017
C++ Guns - Why isn't there a swap function in Fortran and C?
Because Fortran and C sucks. To implement a generic swap function which works for any type and any custom type, one needs templates. Think about usually variables which store a value. Templates are variables which store types. But Fortran and C do not have template techniques. So one must implement a swap function for every […]
Comments Off on C++ Guns - Why isn't there a swap function in Fortran and C?
26.01.2016
Evaluation of logical operations
Spass mit dem Standard. Aus dem Fortran 90/95 Standard [1] Kapitel 7.1.7.6. Evaluation of logical intrinsic operations The rules given in 7.2.4 specify the interpretation of logical intrinsic operations. Once the interpretation of an expression has been established in accordance with those rules, the processor may evaluate any other expression that is logically equivalent, provided […]
Comments Off on Evaluation of logical operations
29.05.2015
warning: conversion to 'float' from 'int' may alter its value [-Wconversion] (Bug of the day 7)
Another bug of the day :D You can do the following float var = float(vari); // yes I know I'm loosing precision int var = int(std::floor(varf)) // yes I know interger can overflow int var = qFloor(varf) // Qt version Same for double. warning: comparison between signed and unsigned integer expressions [-Wsign-compare] Tricky one. Usually […]
Comments Off on warning: conversion to 'float' from 'int' may alter its value [-Wconversion] (Bug of the day 7)
20.05.2015
-1 (Bug of the day 5)
vector vecB; vecB.resize(vecA.size()-1); for(size_t i = 0; i < vecA.size(); ++i) { ... vecB[i] = value ... } Na, wer findet ihn? Bei so etwas findet ich QT's QVector wieder besser als den Standard c++ vector. Qt macht zumindest bei Debug Einstellung eine Bereichsüberprüfung. Ausser es wird die at() Funktion statt den operator() benutzt. Dann […]
Comments Off on -1 (Bug of the day 5)
16.05.2015
integer overflow debugger trap
Benutzt man 16bit Integer statt 32bit um Speicher zu sparen und seine cache misses zu optimieren, läuft man Gefahr den Zahlenbereich von -32768 bis +32767 zu verlassen. So wie es für Floatingpoint Zahlen Überprüfungen auf over/underflow etc gibt, die ein Signal werfen bzw den Compiler anspringen lassen, so gibt es das auch für Integer. Ist […]
Comments Off on integer overflow debugger trap
18.02.2015
rosettacode - Simple moving average
http://rosettacode.org/wiki/Averages/Simple_moving_average#C.2B.2B The original rosetta C example shows the usage of variable function arguments. The C++ example shows how to implement a circular buffer. They are confusing and inefficient. My Version shows how to implement a simple moving average using modern c++ techniques. #include < iostream > #include < vector > class SMA { public: SMA(int […]
Comments Off on rosettacode - Simple moving average
02.02.2015
more crazy C
#include #define CACHE 256 enum { h_unknown = 0, h_yes, h_no }; unsigned char buf[CACHE] = {0, h_yes, 0}; int happy(int n) { int sum = 0, x, nn; if (n < CACHE) { if (buf[n]) return 2 - buf[n]; buf[n] = h_no; } for (nn = n; nn; nn /= 10) x = nn […]
02.01.2015
raw speed of C using OO with C++
Programs written in C are very very fast. Those written in C++ can be slower due to the fact that copying object is not alway easy as copying an array of numbers. One have to call the copy constructor maybe with side effects like allocate some space. The language C++ is full backwards compatible to […]
Comments Off on raw speed of C using OO with C++