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Today's topics:
* ===Welcome to comp.lang.c++! Read this first. - 1 messages, 1 author
http://groups.google.com/group/comp.lang.c++/t/d1056f435c150129?hl=en
* dealing with large csv files - 1 messages, 1 author
http://groups.google.com/group/comp.lang.c++/t/67015284d3d3652f?hl=en
* www.cicigogo.cn Nike AirMax,nike shox,Air Jordan,air force one,dunk,UGG,
Adidas - 1 messages, 1 author
http://groups.google.com/group/comp.lang.c++/t/b2e93d58cfac142c?hl=en
* Who gets higher salary a Java Programmer or a C++ Programmer? - 1 messages,
1 author
http://groups.google.com/group/comp.lang.c++/t/4017272356b778c8?hl=en
==============================================================================
TOPIC: ===Welcome to comp.lang.c++! Read this first.
http://groups.google.com/group/comp.lang.c++/t/d1056f435c150129?hl=en
==============================================================================
== 1 of 1 ==
Date: Sat, Nov 29 2008 9:29 pm
From: Shiva
Welcome to comp.lang.c++! Read this first.
This post is intended to give the new reader an introduction to reading
and posting in this newsgroup. We respectfully request that you read
all the way through this post, as it helps make for a more pleasant
and useful group for everyone.
First of all, please keep in mind that comp.lang.c++ is a group for discussion
of general issues of the C++ programming language, as defined by the ANSI/ISO
language standard. If you have a problem that is specific to a particular system
or compiler, you are much more likely to get complete and accurate answers in a
group that specializes in your platform. A listing of some newsgroups is given
at the end of this post.
The FAQ (Frequently Asked Question) list has a wealth of information for
both the new and veteran C++ programmer. No matter what your experience
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The comp.lang.c++ FAQ is available at http://www.parashift.com/c++-faq-lite/
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are happy to assist with problems of standard C++. We have only a few
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Some netiquette topics which frequently crop up on comp.lang.c++ are
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http://www.parashift.com/c++-faq-lite/how-to-post.html#faq-5.10
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http://www.parashift.com/c++-faq-lite/how-to-post.html#faq-5.11
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http://www.parashift.com/c++-faq-lite/how-to-post.html#faq-5.12
A note on comp.lang.c++ etiquette: Accuracy is valued very highly in this
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This is a very busy group, so these requests are designed to make it as
pleasant and efficient an experience as possible. We hope it proves
a valuable commodity to you.
A list of some Newsgroups :
Languages and Programming
-------------------------
comp.lang.c The C Programming Language
comp.lang.asm.x86 x86 assembly language programming
comp.programming Non-language specific programming
comp.graphics.algorithms Issues of computer graphics
Operating Systems
-----------------
comp.os.msdos.programmer DOS, BIOS, Memory Models, interrupts,
screen handling, hardware
comp.os.ms-windows.programmer.win32 MS/Windows: Mice, DLLs, hardware
comp.os.os2.programmer.misc OS/2 Programming
comp.sys.mac.programmer.misc Macintosh Programming
comp.unix.programmer General Unix: processes, pipes, POSIX,
curses, sockets
comp.unix.[vendor] Various Unix vendors
Microsoft VC++
-------------
microsoft.public.vc.language VC++ issues
microsoft.public.vc.mfc MFC Issues
microsoft.public.dotnet.languages.vc C++/CLR Issues
microsoft.public.dotnet.framework .Net Framework
Borland C++ Builder
-------------------
borland.public.cppbuilder.language Borland C++ Builder
borland.public.cpp.language
borland.public.cppbuilder
-Shiva
http://www.slack.net/~shiva/welcome.txt
Sun Nov 30 00:30:00 EST 2008
==============================================================================
TOPIC: dealing with large csv files
http://groups.google.com/group/comp.lang.c++/t/67015284d3d3652f?hl=en
==============================================================================
== 1 of 1 ==
Date: Sat, Nov 29 2008 10:32 pm
From: LR
brzak wrote:
> hi
>
> I was hoping for a few pointers on how to best go about
> processing large csv files.
I don't think that you've given enough information about your particular
problem, but I'll give it a try.
>
> The files:
> a typical file has 100K-500K records
> approx 150 chars per line (10 'fields')
> so file sizes of 15MB-75MB.
>
> The processing:
> summarise numerical fields based on conditions applied to other
> fields
>
> the resulting summary is a table;
> the column headers of which are the list of unique values of one
> field
> the row headers are decided upon by conditions on other fields
> (this may include lookups, exclusions, reclassifications)
Do you mean a hierarchical file, or some other structure?
>
> Taking into account the size of the files, and number of operations
> requierd on each record...
>
> What if any of thse considerations do I need to take into account:
>
> -is the file read in line by line / or in one go?
I'd probably try to do it line by line first and get the processing
right, and then if you need to, switch to all in one go.
> +if in one go, there would be issues with available memory?
There will be issues no matter how you write your code, but the question
is do you have enough memory to store the entire text or not? Plus the
space required for the variables you're going to manipulate?
> +if it's line by line, is tehre a significant difference in time
> taken to process? (i.e from my limited personal experience with
> VBA, reading/writing a cell at a time in a spreasheet is far
> slower than reading/writing in 'batches')
Very system dependent. And "batch" size dependent. You'll have to try it
and see.
> +or would it be an idea to read a limited number in one go?
> e.g. deal with 20,000 at a time in memory
Depends on what your data is like and what you have to do with it.
> i suppose this question demonstrates a lack of experience with C++
> but hey, that's why i'm posting in the learner's forum :)
>
> -however much of the file is read, is it worth writing a bespoke
> solution
> or look for a parser/class that's been written for csv files?
Reading in csv files isn't difficult. You do mean comma seperated
values? What have you tried so far?
> +perhaps there is a module that i can import?
Have you looked at std::getline? You can use that not only to read a
line at a time, but once you have a line in a std::string to easily get
values that are separated by commas using a std::istringstream. Unless
you have quoted fields with commas in them. In which case you might be
more interested in something that can deal with regular expressions.
You might want to look at www.boost.org, or perhaps if your compiler has
support for it, the tr1. I did a quick google(tm) and found this, but I
don't know how good it is: http://www.johndcook.com/cpp_regex.html
But I think that std::getline should be something to take a look at first.
> +since the csv files are *supposed* to be of a standard format,
What standard are they following? And do you suspect they don't follow a
standard?
> would
> there be much to gain iin writing something specific to this - this
> would be done with the aim of reducing processing time
Have you tried this already and found that your processing time is too long?
>
> -data types... should i read the value fields as floating point
> numbers (range approx. +/- 500000.00)
Probably that or double. I think double would be better. But as you
point out...
> +will using floating point data types save memory?
Yes, well probably, but I suspect it will take more time to use float.
System dependent. But I don't know. Best to benchmark if you're
concerned. Also, I don't recall, but I think that sizeof(float) can be
equal to sizeof(double), although I can't think of a system where it is.
I think that most problems have a space time trade off. You may have to
decide which one is more important to you.
> As anyone reading would be able to tell, I'm still quite new to this
> language, and am missing some of the basics which I've had a bit of
> trouble locating solutions to.
>
> Any advice would be much appreciated!
Sounds like you might need a good book. You might want to check out the
reviews at www.accu.org.
LR
==============================================================================
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http://groups.google.com/group/comp.lang.c++/t/b2e93d58cfac142c?hl=en
==============================================================================
== 1 of 1 ==
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==============================================================================
TOPIC: Who gets higher salary a Java Programmer or a C++ Programmer?
http://groups.google.com/group/comp.lang.c++/t/4017272356b778c8?hl=en
==============================================================================
== 1 of 1 ==
Date: Sun, Nov 30 2008 12:02 am
From: Tim Smith
In article <6pdnoaF7hqv1U3@mid.individual.net>,
blmblm@myrealbox.com <blmblm@myrealbox.com> wrote:
> In article <49305b9b$0$90271$14726298@news.sunsite.dk>,
> Arne Vajhøj <arne@vajhoej.dk> wrote:
> Oh, I don't know that you can really go by that -- some schools
> apparently offer a degree called "Bachelor of Science in Business
> Administration". (But maybe I shouldn't be too snide -- perhaps
> what's taught in business courses *is* a science in some way.
> "Just sayin", maybe.)
"Science" can mean a systematically organized body of knowledge on a
particular subject. Some schools, such as Caltech and MIT, only offer
the B.S. to undergraduates. So, if you went to Caltech and majored in
English literature (which you can, in fact, do), you would end up with a
Bachelor of Science in English Literature. And some schools only offer
the B.A. degree to undergraduates, so if you went to one of those, and
majored in physics, you'd end up with a Bachelor of Arts in physics.
You can see this use of "science" in the United States Constitution.
One of the powers given to Congress is:
To promote the progress of science and useful arts, by securing for
limited times to authors and inventors the exclusive right to their
respective writings and discoveries
That's what authorizes both copyrights and patents in the United States.
Note that it matches up "science" with "writings" of "authors", and
"useful arts" with "discoveries" of "inventors".
--
--Tim Smith
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