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153 lines
3.9 KiB
153 lines
3.9 KiB
#include "clapack.h" |
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/* Table of constant values */ |
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static integer c__1 = 1; |
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doublereal slanst_(char *norm, integer *n, real *d__, real *e) |
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{ |
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/* System generated locals */ |
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integer i__1; |
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real ret_val, r__1, r__2, r__3, r__4, r__5; |
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/* Builtin functions */ |
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double sqrt(doublereal); |
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/* Local variables */ |
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integer i__; |
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real sum, scale; |
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extern logical lsame_(char *, char *); |
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real anorm; |
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extern /* Subroutine */ int slassq_(integer *, real *, integer *, real *, |
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real *); |
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/* -- LAPACK auxiliary routine (version 3.1) -- */ |
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/* Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */ |
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/* November 2006 */ |
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/* .. Scalar Arguments .. */ |
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/* .. */ |
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/* .. Array Arguments .. */ |
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/* .. */ |
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/* Purpose */ |
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/* ======= */ |
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/* SLANST returns the value of the one norm, or the Frobenius norm, or */ |
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/* the infinity norm, or the element of largest absolute value of a */ |
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/* real symmetric tridiagonal matrix A. */ |
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/* Description */ |
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/* =========== */ |
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/* SLANST returns the value */ |
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/* SLANST = ( max(abs(A(i,j))), NORM = 'M' or 'm' */ |
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/* ( */ |
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/* ( norm1(A), NORM = '1', 'O' or 'o' */ |
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/* ( */ |
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/* ( normI(A), NORM = 'I' or 'i' */ |
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/* ( */ |
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/* ( normF(A), NORM = 'F', 'f', 'E' or 'e' */ |
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/* where norm1 denotes the one norm of a matrix (maximum column sum), */ |
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/* normI denotes the infinity norm of a matrix (maximum row sum) and */ |
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/* normF denotes the Frobenius norm of a matrix (square root of sum of */ |
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/* squares). Note that max(abs(A(i,j))) is not a consistent matrix norm. */ |
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/* Arguments */ |
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/* ========= */ |
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/* NORM (input) CHARACTER*1 */ |
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/* Specifies the value to be returned in SLANST as described */ |
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/* above. */ |
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/* N (input) INTEGER */ |
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/* The order of the matrix A. N >= 0. When N = 0, SLANST is */ |
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/* set to zero. */ |
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/* D (input) REAL array, dimension (N) */ |
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/* The diagonal elements of A. */ |
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/* E (input) REAL array, dimension (N-1) */ |
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/* The (n-1) sub-diagonal or super-diagonal elements of A. */ |
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/* ===================================================================== */ |
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/* .. Parameters .. */ |
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/* .. */ |
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/* .. Local Scalars .. */ |
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/* .. */ |
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/* .. External Functions .. */ |
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/* .. */ |
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/* .. External Subroutines .. */ |
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/* .. */ |
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/* .. Intrinsic Functions .. */ |
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/* .. */ |
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/* .. Executable Statements .. */ |
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/* Parameter adjustments */ |
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--e; |
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--d__; |
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/* Function Body */ |
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if (*n <= 0) { |
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anorm = 0.f; |
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} else if (lsame_(norm, "M")) { |
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/* Find max(abs(A(i,j))). */ |
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anorm = (r__1 = d__[*n], dabs(r__1)); |
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i__1 = *n - 1; |
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for (i__ = 1; i__ <= i__1; ++i__) { |
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/* Computing MAX */ |
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r__2 = anorm, r__3 = (r__1 = d__[i__], dabs(r__1)); |
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anorm = dmax(r__2,r__3); |
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/* Computing MAX */ |
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r__2 = anorm, r__3 = (r__1 = e[i__], dabs(r__1)); |
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anorm = dmax(r__2,r__3); |
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/* L10: */ |
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} |
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} else if (lsame_(norm, "O") || *(unsigned char *) |
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norm == '1' || lsame_(norm, "I")) { |
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/* Find norm1(A). */ |
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if (*n == 1) { |
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anorm = dabs(d__[1]); |
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} else { |
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/* Computing MAX */ |
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r__3 = dabs(d__[1]) + dabs(e[1]), r__4 = (r__1 = e[*n - 1], dabs( |
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r__1)) + (r__2 = d__[*n], dabs(r__2)); |
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anorm = dmax(r__3,r__4); |
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i__1 = *n - 1; |
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for (i__ = 2; i__ <= i__1; ++i__) { |
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/* Computing MAX */ |
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r__4 = anorm, r__5 = (r__1 = d__[i__], dabs(r__1)) + (r__2 = |
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e[i__], dabs(r__2)) + (r__3 = e[i__ - 1], dabs(r__3)); |
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anorm = dmax(r__4,r__5); |
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/* L20: */ |
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} |
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} |
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} else if (lsame_(norm, "F") || lsame_(norm, "E")) { |
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/* Find normF(A). */ |
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scale = 0.f; |
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sum = 1.f; |
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if (*n > 1) { |
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i__1 = *n - 1; |
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slassq_(&i__1, &e[1], &c__1, &scale, &sum); |
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sum *= 2; |
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} |
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slassq_(n, &d__[1], &c__1, &scale, &sum); |
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anorm = scale * sqrt(sum); |
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} |
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ret_val = anorm; |
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return ret_val; |
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/* End of SLANST */ |
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} /* slanst_ */
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