Fstream write to binary file

I want to point you to the "Some calculations to fill a[]" part. Which I think is essential. You generate a[], then you copy from a[] to an output buffer thats what fstream::write does , then you generate again, etc. Also, when writing lots of data to files it is sometimes faster to logically extend the file size instead of physically, this is because when logically extending a file the file system does not zero the new space out before writing to it.

It is also smart to logically extend the file more than you actually need to prevent lots of file extentions. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Ask Question. Asked 9 years, 6 months ago.

Active 1 year, 6 months ago. Viewed k times. Any ideas how I can speed up my writing? Dominic Hofer Dominic Hofer 5, 4 4 gold badges 15 15 silver badges 23 23 bronze badges. Did your timing results exclude the time it takes to do your computations to fill a[]? I've actually done this task before.

Copying something is not the same as writing arbitrary values to a random access file. MaximYegorushkin: Link or it didn't happen. Show 17 more comments. Active Oldest Votes.

Thanks a lot to everyone. SChepurin: If you're being pedantic, probably not. If you're being practical, probably yes. I'm just curious how big difference there is between using this line and not, but I don't have the fast enough disk to check the corner case. And if there is any real difference. Show 10 more comments. Try the following, in order: Smaller buffer size. Check any benchmark results posted online.

You need either 4kB writes with a queue depth of 32 or more, or else K or higher writes, to get any sort of decent throughput. BenVoigt: Yup, that correlates with me saying KiB was the sweet spot for me. From my experience, smaller buffer sizes are usually optimal.

Add a comment. Between buffering and non buffering. Also note: SSD drives "tend" to slow down lower transfer rates as they fill up. SSD drives "tend" to slow down lower transfer rates as they get older because of non working bits. Edit I changed my code to use the lower level calls: ie no buffering. Community Bot 1 1 1 silver badge. Martin York Martin York k 80 80 gold badges silver badges bronze badges.

I didn't downvote, but your buffer size is too small. Mysticial: It surprises my that buffer size makes a difference though I believe you. The buffer is useful when you have lots of small writes so that the underlying device is not bothered with many requests. As such the data should be passed directly to the underlying device thus by-passing the buffer. Though if you see a difference this would contradict this and make my wonder why the write is actually using a buffer at all.

The best solution is NOT to increase the buffer size but to remove the buffer and make write pass the data directly to the underlying device. If you're under Windows, this can result in a premature end of file, and some programs seem to have problems with new lines written inbinary, when reading in text mode. I think for now I have things working the way I need them, hopefully I won't encounter these problems again!

Have a good new year, Rory. This discussion thread is closed Start new discussion. Campbell last post: by. NET Framework. Opening, reading and writing binary data to file. Trouble reading a binary file as float values.

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Dec 30 '07 Follow Post Reply 10 Barry rory wrote: I can't seem to append a string to the end of a binary file. Jan 3 '08 This discussion thread is closed Start new discussion Replies have been disabled for this discussion. Posted: 6 days ago The parameters types require a little bit of explanation. The buffer pointer is of type voidthis allows for any type of variable to be used as the first parameter. You should not be writing fun c tions with void parameters, thisis a very tri c ky part of programming.

The type streamsizeissimply a po…. Posted: 1 week ago fstream. File streams are asso c iated with files either on c onstru c tion, or …. The stream obje c t then has to be opened for input or output or both. To append text to the file, the stream has to be opened for appending. The file is extended if the put pointer is c urrent at the end of the file. Posted: 3 days ago Answer 1 of 2 : It depends upon the level at whi c h you are programming.

You may want to save file with. However there is an easier way too and we may dis c uss both. If you c an c hoose one of these formats then I c an give you some help. If you have to work old ex c el formats then you are in trouble! The fun c tion takes this syntax: void c lose ; How to Write to Files. The text to be written to the file should be en c losed within double-quotes. We c an read the spe c ified text file through the open fun c tion. There are many types of modes: The following is a dire c t program to demonstrate how to That's c orre c t.