text: #include "blaswrap.h"
  #include "f2c.h"
  
  /* Subroutine */ int zpotf2_(char *uplo, integer *n, doublecomplex *a, 
  	integer *lda, integer *info)
  {
  /*  -- LAPACK routine (version 3.0) --   
         Univ. of Tennessee, Univ. of California Berkeley, NAG Ltd.,   
         Courant Institute, Argonne National Lab, and Rice University   
         September 30, 1994   
  
  
      Purpose   
      =======   
  
      ZPOTF2 computes the Cholesky factorization of a complex Hermitian   
      positive definite matrix A.   
  
      The factorization has the form   
         A = U' * U ,  if UPLO = 'U', or   
         A = L  * L',  if UPLO = 'L',   
      where U is an upper triangular matrix and L is lower triangular.   
  
      This is the unblocked version of the algorithm, calling Level 2 BLAS.   
  
      Arguments   
      =========   
  
      UPLO    (input) CHARACTER*1   
              Specifies whether the upper or lower triangular part of the   
              Hermitian matrix A is stored.   
              = 'U':  Upper triangular   
              = 'L':  Lower triangular   
  
      N       (input) INTEGER   
              The order of the matrix A.  N >= 0.   
  
      A       (input/output) COMPLEX*16 array, dimension (LDA,N)   
              On entry, the Hermitian matrix A.  If UPLO = 'U', the leading   
              n by n upper triangular part of A contains the upper   
              triangular part of the matrix A, and the strictly lower   
              triangular part of A is not referenced.  If UPLO = 'L', the   
              leading n by n lower triangular part of A contains the lower   
              triangular part of the matrix A, and the strictly upper   
              triangular part of A is not referenced.   
  
              On exit, if INFO = 0, the factor U or L from the Cholesky   
              factorization A = U'*U  or A = L*L'.   
  
      LDA     (input) INTEGER   
              The leading dimension of the array A.  LDA >= max(1,N).   
  
      INFO    (output) INTEGER   
              = 0: successful exit   
              < 0: if INFO = -k, the k-th argument had an illegal value   
              > 0: if INFO = k, the leading minor of order k is not   
                   positive definite, and the factorization could not be   
                   completed.   
  
      =====================================================================   
  
  
         Test the input parameters.   
  
         Parameter adjustments */
      /* Table of constant values */
      static doublecomplex c_b1 = {1.,0.};
      static integer c__1 = 1;
      
      /* System generated locals */
      integer a_dim1, a_offset, i__1, i__2, i__3;
      doublereal d__1;
      doublecomplex z__1, z__2;
      /* Builtin functions */
      double sqrt(doublereal);
      /* Local variables */
      static integer j;
      extern logical lsame_(char *, char *);
      extern /* Double Complex */ VOID zdotc_(doublecomplex *, integer *, 
  	    doublecomplex *, integer *, doublecomplex *, integer *);
      extern /* Subroutine */ int zgemv_(char *, integer *, integer *, 
  	    doublecomplex *, doublecomplex *, integer *, doublecomplex *, 
  	    integer *, doublecomplex *, doublecomplex *, integer *);
      static logical upper;
      extern /* Subroutine */ int xerbla_(char *, integer *), zdscal_(
  	    integer *, doublereal *, doublecomplex *, integer *), zlacgv_(
  	    integer *, doublecomplex *, integer *);
      static doublereal ajj;
  #define a_subscr(a_1,a_2) (a_2)*a_dim1 + a_1
  #define a_ref(a_1,a_2) a[a_subscr(a_1,a_2)]
  
  
      a_dim1 = *lda;
      a_offset = 1 + a_dim1 * 1;
      a -= a_offset;
  
      /* Function Body */
      *info = 0;
      upper = lsame_(uplo, "U");
      if (! upper && ! lsame_(uplo, "L")) {
  	*info = -1;
      } else if (*n < 0) {
  	*info = -2;
      } else if (*lda < max(1,*n)) {
  	*info = -4;
      }
      if (*info != 0) {
  	i__1 = -(*info);
  	xerbla_("ZPOTF2", &i__1);
  	return 0;
      }
  
  /*     Quick return if possible */
  
      if (*n == 0) {
  	return 0;
      }
  
      if (upper) {
  
  /*        Compute the Cholesky factorization A = U'*U. */
  
  	i__1 = *n;
  	for (j = 1; j <= i__1; ++j) {
  
  /*           Compute U(J,J) and test for non-positive-definiteness. */
  
  	    i__2 = a_subscr(j, j);
  	    d__1 = a[i__2].r;
  	    i__3 = j - 1;
  	    zdotc_(&z__2, &i__3, &a_ref(1, j), &c__1, &a_ref(1, j), &c__1);
  	    z__1.r = d__1 - z__2.r, z__1.i = -z__2.i;
  	    ajj = z__1.r;
  	    if (ajj <= 0.) {
  		i__2 = a_subscr(j, j);
  		a[i__2].r = ajj, a[i__2].i = 0.;
  		goto L30;
  	    }
  	    ajj = sqrt(ajj);
  	    i__2 = a_subscr(j, j);
  	    a[i__2].r = ajj, a[i__2].i = 0.;
  
  /*           Compute elements J+1:N of row J. */
  
  	    if (j < *n) {
  		i__2 = j - 1;
  		zlacgv_(&i__2, &a_ref(1, j), &c__1);
  		i__2 = j - 1;
  		i__3 = *n - j;
  		z__1.r = -1., z__1.i = 0.;
  		zgemv_("Transpose", &i__2, &i__3, &z__1, &a_ref(1, j + 1), 
  			lda, &a_ref(1, j), &c__1, &c_b1, &a_ref(j, j + 1), 
  			lda);
  		i__2 = j - 1;
  		zlacgv_(&i__2, &a_ref(1, j), &c__1);
  		i__2 = *n - j;
  		d__1 = 1. / ajj;
  		zdscal_(&i__2, &d__1, &a_ref(j, j + 1), lda);
  	    }
  /* L10: */
  	}
      } else {
  
  /*        Compute the Cholesky factorization A = L*L'. */
  
  	i__1 = *n;
  	for (j = 1; j <= i__1; ++j) {
  
  /*           Compute L(J,J) and test for non-positive-definiteness. */
  
  	    i__2 = a_subscr(j, j);
  	    d__1 = a[i__2].r;
  	    i__3 = j - 1;
  	    zdotc_(&z__2, &i__3, &a_ref(j, 1), lda, &a_ref(j, 1), lda);
  	    z__1.r = d__1 - z__2.r, z__1.i = -z__2.i;
  	    ajj = z__1.r;
  	    if (ajj <= 0.) {
  		i__2 = a_subscr(j, j);
  		a[i__2].r = ajj, a[i__2].i = 0.;
  		goto L30;
  	    }
  	    ajj = sqrt(ajj);
  	    i__2 = a_subscr(j, j);
  	    a[i__2].r = ajj, a[i__2].i = 0.;
  
  /*           Compute elements J+1:N of column J. */
  
  	    if (j < *n) {
  		i__2 = j - 1;
  		zlacgv_(&i__2, &a_ref(j, 1), lda);
  		i__2 = *n - j;
  		i__3 = j - 1;
  		z__1.r = -1., z__1.i = 0.;
  		zgemv_("No transpose", &i__2, &i__3, &z__1, &a_ref(j + 1, 1), 
  			lda, &a_ref(j, 1), lda, &c_b1, &a_ref(j + 1, j), &
  			c__1);
  		i__2 = j - 1;
  		zlacgv_(&i__2, &a_ref(j, 1), lda);
  		i__2 = *n - j;
  		d__1 = 1. / ajj;
  		zdscal_(&i__2, &d__1, &a_ref(j + 1, j), &c__1);
  	    }
  /* L20: */
  	}
      }
      goto L40;
  
  L30:
      *info = j;
  
  L40:
      return 0;
  
  /*     End of ZPOTF2 */
  
  } /* zpotf2_ */
  
  #undef a_ref
  #undef a_subscr
  
  
  