Re: Execution speed Nim vs. Python
(I should perhaps qualify beyond -d:release using gcc or clang with high optimization levels on the back end since jil210 revealed in [another thread](https://forum.nim-lang.org/t/3198) the baseline 5X performance mystery arose from using tcc as a back end.) Also, for the curious, the reason C++ STL will usually underperform Nim's hash tables in benchmarks like this is that STL iterator deletion semantics make the natural STL hash table collision resolution implementation choice be external chaining. Those extra linked list indirections add latency, especially when tables do not fit in on-CPU cache.
Re: Execution speed Nim vs. Python
Nim `Table` and `HashSet` should be caching the hash code values in their tables and also using that as a "comparison prefix" (comparing string values only if the integer hash codes already match). The string hash of the new inputs is ineliminable - or rather has to be done at least once anyway. My guess is the lines are long-ish (greater than 10 chars, say). The default Nim hash string function could be faster, especially for longer strings. E.g., the current default does byte-at-a-time manipulations and usually 8-byte/word-at-a-time can get about as good bit mixing much faster, especially for long strings like lines in files. Such a replacement might take that 60% hashing time in this particular benchmark down to 10-15% for a 2X-ish overall speed up. I have benchmarked C++ for these kinds of tests and I suspect the current STL would not be faster than Nim with the -d:release in this case. (C++, too could benefit from faster default string hash).
Re: perfomance of set/hashset operation between python and nim
kcachegrind: nim -d:release --debugger:native c mydiff valgrind --tool=callgrind ./mydiff file1 file2 kcachegrind callgrind.out.* Also used here for example: [https://hookrace.net/blog/writing-an-async-logger-in-nim/#optimization](https://hookrace.net/blog/writing-an-async-logger-in-nim/#optimization)
Re: Problem with nim types i guess
I solved it by putting j in the function. Why has the compile a problem when it
is outside of the proc?
import json, asynchttpserver, asyncdispatch
var server = newAsyncHttpServer()
proc cb(req: Request) {.async.} =
var j = %* {
"test": 1,
"test2": "42",
}
await req.respond(Http200, j.pretty())
waitFor server.serve(Port(8080), cb)
Re: perfomance of set/hashset operation between python and nim
@def What program is that?
Re: perfomance of set/hashset operation between python and nim
Just to add to the conversation: Each file is 1.7MB **System specs** OS: Ubuntu 16.04 xenial Kernel: x86_64 Linux 4.4.0-83-generic CPU: Intel Core i5-6600K @ 3.9GHz RAM: 15980MiB **Python 2.7** $ time python test1.py test1.log test1-2.log real0m0.042s user0m0.040s sys 0m0.000s **Nim 0.17.2** $ nim c -d:release test1.nim $ time ./test1 test1.log test1-2.log real0m0.056s user0m0.044s sys 0m0.008s **Nim 0.17.2 (DEBUG)** $ nim c -o:test1-dev test1.nim $ time ./test1-dev test1.log test1-2.log real0m0.273s user0m0.264s sys 0m0.008s Times seem correct to me. We have to remember that the majority of Python's file I/O stuff is implemented in C. The fact that Nim is ever so slightly slower than native compiled C is not surprising. On my system, compiling with `-d:release` gives a 5x speed increase. This is also not surprising.
Re: perfomance of set/hashset operation between python and nim
Of course gcc will optimize much better than tcc! Also put your nim code in a proc for some more performance. Here's what parts are taking most of the time: [https://i.imgur.com/hLaOHVe.png](https://i.imgur.com/hLaOHVe.png)
Re: perfomance of set/hashset operation between python and nim
Now I resolved this issue using gcc rather than tcc. tcc version took 25 sec while gcc version 5 sec comparable to python version! I thought tcc faster than gcc but nim using gcc makes faster on linux.
Re: Execution speed Nim vs. Python
Python caches hashing of strings. Nim does not (it would be a challenge, as Nim strings are mutable). I suggest using string references or Hash objects if you want to compare performance. Has anyone benchmarked C++ for this kind of test?
Problem with nim types i guess
Hello I am new to nim. I have the following code and i don't understand what is
wrong.
* * *
import json, asynchttpserver, asyncdispatch
var server = newAsyncHttpServer()
var j = %* {
"test": 1,
"test2": "42",
}
proc cb(req: Request) {.async.} =
await req.respond(Http200, json.pretty(j))
waitFor server.serve(Port(8080), cb)
**Error**:
main.nim(13, 15) Error: type mismatch: got (AsyncHttpServer, Port, proc (req:
Request): Future[system.void]{.locks: .}) but expected one of:
proc serve(server: AsyncHttpServer; port: Port;
callback: proc (request: Request): Future[void]; address = ""): Future[void]
Nimx installation issue
Hi, I tried to install nimx in Windows 10 with the following: E:Nim-0.17.2>nimble install nimx Downloading [https://github.com/yglukhov/nimx](https://github.com/yglukhov/nimx) using git Tip: 1 messages have been suppressed, use --verbose to show them. Error: 'git' not in PATH. However, it failed. Pls advice how to solve this.
Re: perfomance of set/hashset operation between python and nim
thanks for testing. I was doing it with 148Mb files and I will try to revise as you suggested and recompile with -d:release. sure I did it before, though. Yes, i like nim but this performance issue should be resolved somehow.
Re: perfomance of set/hashset operation between python and nim
I tested for 7.7 mb files: python2 ... 0,54s user 0,23s system 54% cpu 1,417 total nim release ... 0,56s user 0,18s system 54% cpu 1,337 total nim debug ... 3,96s user 0,30s system 99% cpu 4,262 total Perhaps a stupid question, but you compile with --d:release? By the way you can replace it: let file1 = open(paramStr(1)) let file2 = open(paramStr(2)) let old_lines = file1.readAll().splitLines() let new_lines = file2.readAll().splitLines() file1.close() file2.close() on this: let old_lines = readFile(paramStr(1)).splitLines() let new_lines = readFile(paramStr(2)).splitLines()
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Re: newb saying Hi
Thanx for the pointer will check it out
