Free Pascal

Bit-packed structure (record) in Free Pascal and Delphi

Submitted by st on

Here is the code explaining some methods to pack bit accessing logic in your program.

program project1;
 
type
  TRec1 = packed record // Doesn't pack at all
    b1, b2, b3, b4, b5, b6, b7, b8, b9, b10, b11, b12, b13, b14, b15, b16: boolean;
  end;
 
  TRec2 = bitpacked record // Free Pascal specific
    b1, b2, b3, b4, b5, b6, b7, b8, b9, b10, b11, b12, b13, b14, b15, b16: boolean;
  end;
 
  TRecByte = (b1, b2, b3, b4, b5, b6, b7, b8, b9, b10, b11, b12, b13, b14, b15, b16);
  TRecBytes = set of TRecByte;
var
  r1: TRec1;
  r2: TRec2;
  s1: TRecBytes;

Sorted map vs hashed map

Submitted by st on

In theory, hash map structure should be very fast on retrieving by key operations, close to O(1) like for an array. A sorted map (keys are sorted) should be O(log2 N) instead. The following test checks the difference.

Common scenario

We will use one tester class per type of tested structure. The keys are string[10] and are generated randomly in prepared array to avoid additional checks whether the key exists or not.

Delphi and Free Pascal bencmark: array vs TList vs dynamic array

Submitted by st on

Let's perform a simple benchmark testing the random and sequential access to arrays and lists. I would like to compare:

  • static array with predefined size (allocated on stack)
  • TList container class (allocated on heap)
  • dynamic array (allocated on heap)
  • generic Delphi TList or Free Pascal TFPGList (allocated on heap)

I use an array/list of 10M elements of integer and varaint data type. You can change the type definition in "type" section if need to test other cases.

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