How much is a char in a string

[ouadji]

my approach to count how many times is a character in a string.

Faster than other methods, as with "Match pattern + loop" or with "Search and Replace"

[altenbach]

I tpyically don't believe claims of "faster" or "slower" unless I see some benchmarking code and benchmarking results. 😄

[altenbach]

For a string of 8M chars, search&replace is 15% faster. (67ms vs 82ms). Make sure to wire the character to both the search and replace inputs.

[ouadji]

[altenbach]

I am very suspicions about your benchmarking code, you compare apples to oranges: remove all these terminals from inside the loop. Watch out for constant folding. If all inputs ot a function are constants, it might get calculated only once and reused for later iterations, giving you a false very fast speed.

For small strings like in your example, performance is irrelevant, so do it once with a 8M long string input instead. Here you should see a difference.

Here is some code that is 8x faster for a 8M string input:

[ouadji]

oops, a mistake ... the error clusters inside the For Loop 

[altenbach]

Here's a quick comparison of a few methods. There are probably even faster ways.

[ouadji]

I redid the test with a string of 10e6 char
I confirm your results, your "count-method" is the fastest

"There are probably even faster ways" ... 

Faster Than the count-method (??) ... with assembler and a Call Library Function ?
I'd be interested to know how to do that, really.

count : 20 ms

replace : 88ms

spreadsheet : 134 ms

(Q6600 Core2 Quad 3GHz- XP sp3)

I learned something today    (about how to do properly a benchmark test)
thank you altenbach

[Alexander_Sobolev]

count : 10 ms

spreadsheet : 43 ms

replace : 49 ms

When the substring to search is longer, the best method will not work.

Spreadsheet time seems to depend on the number of matches

Lenovo w520 (i7, 8GB, win7 64bit)

[ouadji]

not better     with asm  (call dll library)

count : 21ms

asm : 29 ms