/* blas/source_tbsv_r.h

 *

 * Copyright (C) 1996, 1997, 1998, 1999, 2000 Gerard Jungman

 *

 * 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; either version 3 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.

 *

 * You should have received a copy of the GNU General Public License

 * along with this program; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

 */

{

  const int nonunit = (Diag == CblasNonUnit);

  INDEX i, j;

  const int Trans = (TransA != CblasConjTrans) ? TransA : CblasTrans;

  CHECK_ARGS10(TBSV,order,Uplo,TransA,Diag,N,K,A,lda,X,incX);

  if (N == 0)

    return;

  /* form  x := inv( A )*x */

  if ((order == CblasRowMajor && Trans == CblasNoTrans && Uplo == CblasUpper)

      || (order == CblasColMajor && Trans == CblasTrans && Uplo == CblasLower)) {

    /* backsubstitution */

    INDEX ix = OFFSET(N, incX) + incX * (N - 1);

    for (i = N; i > 0 && i--;) {

      BASE tmp = X[ix];

      const INDEX j_min = i + 1;

      const INDEX j_max = GSL_MIN(N, i + K + 1);

      INDEX jx = OFFSET(N, incX) + j_min * incX;

      for (j = j_min; j < j_max; j++) {

        const BASE Aij = A[lda * i + (j - i)];

        tmp -= Aij * X[jx];

        jx += incX;

      }

      if (nonunit) {

        X[ix] = tmp / A[lda * i + 0];

      } else {

        X[ix] = tmp;

      }

      ix -= incX;

    }

  } else if ((order == CblasRowMajor && Trans == CblasNoTrans && Uplo == CblasLower)

             || (order == CblasColMajor && Trans == CblasTrans && Uplo == CblasUpper)) {

    /* forward substitution */

    INDEX ix = OFFSET(N, incX);

    for (i = 0; i < N; i++) {

      BASE tmp = X[ix];

      const INDEX j_min = (i > K ? i - K : 0);

      const INDEX j_max = i;

      INDEX jx = OFFSET(N, incX) + j_min * incX;

      for (j = j_min; j < j_max; j++) {

        const BASE Aij = A[lda * i + (K + j - i)];

        tmp -= Aij * X[jx];

        jx += incX;

      }

      if (nonunit) {

        X[ix] = tmp / A[lda * i + K];

      } else {

        X[ix] = tmp;

      }

      ix += incX;

    }

  } else if ((order == CblasRowMajor && Trans == CblasTrans && Uplo == CblasUpper)

             || (order == CblasColMajor && Trans == CblasNoTrans && Uplo == CblasLower)) {

    /* form  x := inv( A' )*x */

    /* forward substitution */

    INDEX ix = OFFSET(N, incX);

    for (i = 0; i < N; i++) {

      BASE tmp = X[ix];

      const INDEX j_min = (K > i ? 0 : i - K);

      const INDEX j_max = i;

      INDEX jx = OFFSET(N, incX) + j_min * incX;

      for (j = j_min; j < j_max; j++) {

        const BASE Aji = A[(i - j) + lda * j];

        tmp -= Aji * X[jx];

        jx += incX;

      }

      if (nonunit) {

        X[ix] = tmp / A[0 + lda * i];

      } else {

        X[ix] = tmp;

      }

      ix += incX;

    }

  } else if ((order == CblasRowMajor && Trans == CblasTrans && Uplo == CblasLower)

             || (order == CblasColMajor && Trans == CblasNoTrans && Uplo == CblasUpper)) {

    /* backsubstitution */

    INDEX ix = OFFSET(N, incX) + (N - 1) * incX;

    for (i = N; i > 0 && i--;) {

      BASE tmp = X[ix];

      const INDEX j_min = i + 1;

      const INDEX j_max = GSL_MIN(N, i + K + 1);

      INDEX jx = OFFSET(N, incX) + j_min * incX;

      for (j = j_min; j < j_max; j++) {

        const BASE Aji = A[(K + i - j) + lda * j];

        tmp -= Aji * X[jx];

        jx += incX;

      }

      if (nonunit) {

        X[ix] = tmp / A[K + lda * i];

      } else {

        X[ix] = tmp;

      }

      ix -= incX;

    }

  } else {

    BLAS_ERROR("unrecognized operation");

  }

}