spectral-norm Free Pascal program

{ The Computer Language Benchmarks Game
  https://salsa.debian.org/benchmarksgame-team/benchmarksgame/

  contributed by Ian Osgood
  modified by Vincent Snijders
}

program spectralNorm;


var n,i : integer;
    u,v,tmp : array of double;
    vBv,vv : double;

function A(i,j : integer): double; inline;
begin
  A := 1 / ((i+j)*(i+j+1) div 2 + i+1);
end;

procedure mulAv(var v, Av : array of double);
var i,j : integer;
begin
  for i := low(Av) to high(Av) do
  begin
    Av[i] := 0.0;
    for j := low(v) to high(v) do
      Av[i] := Av[i] + A(i,j) * v[j];
  end;
end;

procedure mulAtv(var v, Atv : array of double);
var i,j : integer;
begin
  for i := low(Atv) to high(Atv) do
  begin
    Atv[i] := 0.0;
    for j := low(v) to high(v) do
      Atv[i] := Atv[i] + A(j,i) * v[j];
  end;
end;

procedure mulAtAv(var v, AtAv : array of double);
begin
  mulAv(v, tmp);
  mulAtv(tmp, AtAv);
end;

begin
  Val(paramstr(1), n, i);
  SetLength(u, n);
  SetLength(v, n);
  SetLength(tmp, n);

  for i := low(u) to high(u) do u[i] := 1.0;

  for i := 1 to 10 do begin mulAtAv(u,v); mulAtAv(v,u) end;

  for i := low(u) to high(u) do
  begin
    vBv := vBv + u[i]*v[i];
    vv  := vv  + v[i]*v[i];
  end;

  writeln(sqrt(vBv/vv):0:9);
end.
    

NOTES:
64-bit Ubuntu quad core
Free Pascal Compiler
version 3.2.2 [2021/05/16]


 Wed, 22 May 2024 22:42:45 GMT

MAKE:
mv spectralnorm.fpascal spectralnorm.pas
/opt/src/fpc-3.2.2/bin/fpc -FuInclude/fpascal -XXs -O3 -Ci- -Cr- -g- -CpCOREAVX -CfAVX -Tlinux -Fi Include/fpascal -oFPASCAL_RUN spectralnorm.pas
Warning: Only one source file supported, changing source file to compile from "Include/fpascal" into "spectralnorm.pas"
Free Pascal Compiler version 3.2.2 [2021/05/16] for x86_64
Copyright (c) 1993-2021 by Florian Klaempfl and others
Target OS: Linux for x86-64
Compiling spectralnorm.pas
spectralnorm.pas(60,12) Warning: Variable "vBv" does not seem to be initialized
spectralnorm.pas(61,12) Warning: Variable "vv" does not seem to be initialized
Linking FPASCAL_RUN
65 lines compiled, 0.8 sec
3 warning(s) issued
mv FPASCAL_RUN spectralnorm.fpascal_run
rm spectralnorm.pas

1.06s to complete and log all make actions

COMMAND LINE:
 ./spectralnorm.fpascal_run 5500

PROGRAM OUTPUT:
1.274224153