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//------------------------------------------------------------------------------
//This Source Code Form is subject to the terms of the Mozilla Public
//License, v. 2.0. If a copy of the MPL was not distributed with this
//file, You can obtain one at http://mozilla.org/MPL/2.0/.
//------------------------------------------------------------------------------
unit RndFunc;
{$MODE Delphi}
interface
uses
SysUtils, Math, SndTypes, Ini;
function RndNormal: Single;
function RndGaussLim(AMean, ALim: Single): Single;
function RndRayleigh(AMean: Single): Single;
function BlocksToSeconds(Blocks: Single): Single;
function SecondsToBlocks(Sec: Single): integer;
function RndUniform: Single;
function RndUShaped: Single;
function RndPoisson(AMean: Single): integer;
implementation
function RndNormal: Single;
begin
repeat
try
Result := Sqrt(-2 * Ln(Random)) * Cos(TWO_PI * Random);
Exit;
except
end;
until
False;
end;
function RndGaussLim(AMean, ALim: Single): Single;
begin
Result := AMean + RndNormal * 0.5 * ALim;
Result := Max(AMean-ALim, Min(AMean+ALim, Result));
end;
function RndRayleigh(AMean: Single): Single;
begin
Result := AMean * Sqrt(-Ln(Random) - Ln(Random));
end;
function SecondsToBlocks(Sec: Single): integer;
begin
Result := Round(DEFAULTRATE / Ini.BufSize * Sec);
end;
function BlocksToSeconds(Blocks: Single): Single;
begin
Result := Blocks * Ini.BufSize / DEFAULTRATE;
end;
function RndUniform: Single;
begin
Result := 2*Random - 1;
end;
function RndUShaped: Single;
begin
Result := Sin(Pi*(Random-0.5));
end;
//http://www.library.cornell.edu/nr/bookcpdf/c7-3.pdf
function RndPoisson(AMean: Single): integer;
var
g, t: Single;
begin
g := Exp(-AMean);
t := 1;
for Result:=0 to 30 do
begin
t := t * Random;
if t <= g then Break;
end;
end;
{
//http://www.esbconsult.com.au/
function RndPoisson(AMean: Single): integer;
var
p,q,p0,u: Extended;
l,m,j,k: integer;
pp: array [1..35] of Extended;
begin
// C A S E B. mu < 10
// START NEW TABLE AND CALCULATE P0 IF NECESSARY
m := Max(1, Trunc (AMean));
l := 0;
p := Exp(-AMean);
q := p;
p0 := p;
// STEP U. UNIFORM SAMPLE FOR INVERSION METHOD
repeat
u := Random;
Result := 0;
if (u <= p0) then Exit;
// STEP T. TABLE COMPARISON UNTIL THE END PP(L) OF THE
// PP-TABLE OF CUMULATIVE POISSON PROBABILITIES
// (0.458=PP(9) FOR MU=10)
if l <> 0 then
begin
j := 1;
if (u > 0.458) then j := Min(l, m);
for k := j to l do
if (u <= pp [k]) then
begin Result := K; Exit; end;
if l = 35 then Continue;
end;
// STEP C. CREATION OF NEW POISSON PROBABILITIES P
// AND THEIR CUMULATIVES Q=PP(K)
l := l + 1; // 150
for k := l to 35 do
begin
p := p * AMean / k;
q := q + p;
pp [k] := q;
if (u <= q) then begin Result := K; Exit; end;
end;
l := 35;
until False;
end;
}
end.
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