File Read / Write in C++

waltersdom · November 23, 2023, 9:26pm

I got to thinking:

" Why have the file_read and file_write components never gotten C++ implementations? "

So, I set about trying to make some, largely as an excuse to teach myself how to do raw file IO in C++.

My implementations can be found here:

I have not exhaustively tested these, but:

All the main framework tests run with my file_read_cc instead of the normal file_read.
The naive benchmark included in demo.sh suggests that on my home PC whilst I had other stuff running / open, the combination of the new implementations is:
- ~100% (2x) faster for:
  - messagesize = up to 64, messagesinfile = false, repeat = false
- ~60 to 80% faster for:
  - messagesize = 128 to 2048, messagesinfile = false, repeat = false
  - Speed decreases as messagesize increases
- ~30% faster for:
  - messagesize = 4096 and 8192, messagesinfile = false, repeat = false
- ~100% (2x) faster for:
  - messagesize up to 512, messagesinfile = false, repeat = true
- ~60% faster for:
  - messagesize = 1024, messagesinfile = false, repeat = true
- ~20% faster for:
  - messagesize = 2048, messagesinfile = false, repeat = true
- ~10% slower for:
  - messagesize = 4096 and 8192, messagesinfile = false, repeat = true

Note: I have only tested file_write with testbias, and the error messages are not particularly descriptive.

Feel free to try these (noting the MIT license) and I do not make any guarantees that they work with all inputs.

waltersdom · November 23, 2023, 9:34pm

For people who prefer graphs to badly formatted text :

Note: On all graphs with two colours of bars, the red ones are C++ (Google Sheets makes it really awkward to set the names of the data sets).