/*************************************************************************
Copyright (c) 1992-2007 The University of Tennessee.  All rights reserved.

Contributors:
    * Sergey Bochkanov (ALGLIB project). Translation from FORTRAN to
      pseudocode.

See subroutines comments for additional copyrights.

>>> SOURCE LICENSE >>>
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation (www.fsf.org); either version 2 of the 
License, or (at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

A copy of the GNU General Public License is available at
http://www.fsf.org/licensing/licenses

>>> END OF LICENSE >>>
*************************************************************************/


namespace alglib {
  public class sblas {
    public static void symmetricmatrixvectormultiply(ref double[,] a,
        bool isupper,
        int i1,
        int i2,
        ref double[] x,
        double alpha,
        ref double[] y) {
      int i = 0;
      int ba1 = 0;
      int ba2 = 0;
      int by1 = 0;
      int by2 = 0;
      int bx1 = 0;
      int bx2 = 0;
      int n = 0;
      double v = 0;
      int i_ = 0;
      int i1_ = 0;

      n = i2 - i1 + 1;
      if (n <= 0) {
        return;
      }

      //
      // Let A = L + D + U, where
      //  L is strictly lower triangular (main diagonal is zero)
      //  D is diagonal
      //  U is strictly upper triangular (main diagonal is zero)
      //
      // A*x = L*x + D*x + U*x
      //
      // Calculate D*x first
      //
      for (i = i1; i <= i2; i++) {
        y[i - i1 + 1] = a[i, i] * x[i - i1 + 1];
      }

      //
      // Add L*x + U*x
      //
      if (isupper) {
        for (i = i1; i <= i2 - 1; i++) {

          //
          // Add L*x to the result
          //
          v = x[i - i1 + 1];
          by1 = i - i1 + 2;
          by2 = n;
          ba1 = i + 1;
          ba2 = i2;
          i1_ = (ba1) - (by1);
          for (i_ = by1; i_ <= by2; i_++) {
            y[i_] = y[i_] + v * a[i, i_ + i1_];
          }

          //
          // Add U*x to the result
          //
          bx1 = i - i1 + 2;
          bx2 = n;
          ba1 = i + 1;
          ba2 = i2;
          i1_ = (ba1) - (bx1);
          v = 0.0;
          for (i_ = bx1; i_ <= bx2; i_++) {
            v += x[i_] * a[i, i_ + i1_];
          }
          y[i - i1 + 1] = y[i - i1 + 1] + v;
        }
      } else {
        for (i = i1 + 1; i <= i2; i++) {

          //
          // Add L*x to the result
          //
          bx1 = 1;
          bx2 = i - i1;
          ba1 = i1;
          ba2 = i - 1;
          i1_ = (ba1) - (bx1);
          v = 0.0;
          for (i_ = bx1; i_ <= bx2; i_++) {
            v += x[i_] * a[i, i_ + i1_];
          }
          y[i - i1 + 1] = y[i - i1 + 1] + v;

          //
          // Add U*x to the result
          //
          v = x[i - i1 + 1];
          by1 = 1;
          by2 = i - i1;
          ba1 = i1;
          ba2 = i - 1;
          i1_ = (ba1) - (by1);
          for (i_ = by1; i_ <= by2; i_++) {
            y[i_] = y[i_] + v * a[i, i_ + i1_];
          }
        }
      }
      for (i_ = 1; i_ <= n; i_++) {
        y[i_] = alpha * y[i_];
      }
    }


    public static void symmetricrank2update(ref double[,] a,
        bool isupper,
        int i1,
        int i2,
        ref double[] x,
        ref double[] y,
        ref double[] t,
        double alpha) {
      int i = 0;
      int tp1 = 0;
      int tp2 = 0;
      double v = 0;
      int i_ = 0;
      int i1_ = 0;

      if (isupper) {
        for (i = i1; i <= i2; i++) {
          tp1 = i + 1 - i1;
          tp2 = i2 - i1 + 1;
          v = x[i + 1 - i1];
          for (i_ = tp1; i_ <= tp2; i_++) {
            t[i_] = v * y[i_];
          }
          v = y[i + 1 - i1];
          for (i_ = tp1; i_ <= tp2; i_++) {
            t[i_] = t[i_] + v * x[i_];
          }
          for (i_ = tp1; i_ <= tp2; i_++) {
            t[i_] = alpha * t[i_];
          }
          i1_ = (tp1) - (i);
          for (i_ = i; i_ <= i2; i_++) {
            a[i, i_] = a[i, i_] + t[i_ + i1_];
          }
        }
      } else {
        for (i = i1; i <= i2; i++) {
          tp1 = 1;
          tp2 = i + 1 - i1;
          v = x[i + 1 - i1];
          for (i_ = tp1; i_ <= tp2; i_++) {
            t[i_] = v * y[i_];
          }
          v = y[i + 1 - i1];
          for (i_ = tp1; i_ <= tp2; i_++) {
            t[i_] = t[i_] + v * x[i_];
          }
          for (i_ = tp1; i_ <= tp2; i_++) {
            t[i_] = alpha * t[i_];
          }
          i1_ = (tp1) - (i1);
          for (i_ = i1; i_ <= i; i_++) {
            a[i, i_] = a[i, i_] + t[i_ + i1_];
          }
        }
      }
    }
  }
}