Learning and perception of Delphi algorithm and data structure [5]: Why isn't the POs function the fastest when positioning a character?

Source: Internet
Author: User
If the first parameter of the POs function is Char rather than string, the compiler will first convert Char to string;

From memory structure to management mechanism, string is far more complex than char.

Therefore, there is still room for optimization in the face of this situation (Char to be located) Pos; after optimization, the speed will be increased by about 5 times.

Test:


 unit unit1; interfaceuses windows, messages, sysutils, variants, classes, graphics, controls, forms, dialogs, stdctrls; Type tform1 = Class (tform) button1: tbutton; Procedure button1click (Sender: tobject); end; var form1: tform1; implementation {$ R *. DFM} // custom POS function Mypos (C: Char; const STR: string): integer; var I: integer; begin result: = 0; for I: = 1 to length (STR) do if C = STR [I] Then begin result: = I; Exit End; end; {comparison test} procedure tform1.button1click (Sender: tobject ); vaR S: string; C: Char; I: integer; N: Cardinal; begin S: = 'abcdefghijklmnopqrstuvwxy'; randomize; C: = CHR (random (26) + 97 ); {random .. Z character} {use POS function} n: = gettickcount; for I: = 1 to 1000000 do pos (C, S); N: = gettickcount-N; text: = inttostr (n) + '-'; {use the custom Mypos function} n: = gettickcount; for I: = 1 to 1000000 do Mypos (C, S); N: = gettickcount-N; text: = text + inttostr (n); button1.caption: = 'pos and Mypos speed test'; end.

   

Contact Us

The content source of this page is from Internet, which doesn't represent Alibaba Cloud's opinion; products and services mentioned on that page don't have any relationship with Alibaba Cloud. If the content of the page makes you feel confusing, please write us an email, we will handle the problem within 5 days after receiving your email.

If you find any instances of plagiarism from the community, please send an email to: info-contact@alibabacloud.com and provide relevant evidence. A staff member will contact you within 5 working days.

A Free Trial That Lets You Build Big!

Start building with 50+ products and up to 12 months usage for Elastic Compute Service

  • Sales Support

    1 on 1 presale consultation

  • After-Sales Support

    24/7 Technical Support 6 Free Tickets per Quarter Faster Response

  • Alibaba Cloud offers highly flexible support services tailored to meet your exact needs.