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116 lines
3.2 KiB
116 lines
3.2 KiB
/* dlassq.f -- translated by f2c (version 20061008). |
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You must link the resulting object file with libf2c: |
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on Microsoft Windows system, link with libf2c.lib; |
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on Linux or Unix systems, link with .../path/to/libf2c.a -lm |
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or, if you install libf2c.a in a standard place, with -lf2c -lm |
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-- in that order, at the end of the command line, as in |
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cc *.o -lf2c -lm |
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Source for libf2c is in /netlib/f2c/libf2c.zip, e.g., |
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http://www.netlib.org/f2c/libf2c.zip |
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*/ |
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#include "clapack.h" |
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/* Subroutine */ int dlassq_(integer *n, doublereal *x, integer *incx, |
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doublereal *scale, doublereal *sumsq) |
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{ |
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/* System generated locals */ |
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integer i__1, i__2; |
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doublereal d__1; |
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/* Local variables */ |
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integer ix; |
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doublereal absxi; |
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/* -- LAPACK auxiliary routine (version 3.2) -- */ |
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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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/* DLASSQ returns the values scl and smsq such that */ |
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/* ( scl**2 )*smsq = x( 1 )**2 +...+ x( n )**2 + ( scale**2 )*sumsq, */ |
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/* where x( i ) = X( 1 + ( i - 1 )*INCX ). The value of sumsq is */ |
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/* assumed to be non-negative and scl returns the value */ |
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/* scl = max( scale, abs( x( i ) ) ). */ |
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/* scale and sumsq must be supplied in SCALE and SUMSQ and */ |
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/* scl and smsq are overwritten on SCALE and SUMSQ respectively. */ |
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/* The routine makes only one pass through the vector x. */ |
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/* Arguments */ |
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/* ========= */ |
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/* N (input) INTEGER */ |
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/* The number of elements to be used from the vector X. */ |
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/* X (input) DOUBLE PRECISION array, dimension (N) */ |
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/* The vector for which a scaled sum of squares is computed. */ |
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/* x( i ) = X( 1 + ( i - 1 )*INCX ), 1 <= i <= n. */ |
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/* INCX (input) INTEGER */ |
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/* The increment between successive values of the vector X. */ |
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/* INCX > 0. */ |
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/* SCALE (input/output) DOUBLE PRECISION */ |
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/* On entry, the value scale in the equation above. */ |
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/* On exit, SCALE is overwritten with scl , the scaling factor */ |
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/* for the sum of squares. */ |
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/* SUMSQ (input/output) DOUBLE PRECISION */ |
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/* On entry, the value sumsq in the equation above. */ |
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/* On exit, SUMSQ is overwritten with smsq , the basic sum of */ |
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/* squares from which scl has been factored out. */ |
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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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/* .. Intrinsic Functions .. */ |
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/* .. */ |
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/* .. Executable Statements .. */ |
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/* Parameter adjustments */ |
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--x; |
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/* Function Body */ |
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if (*n > 0) { |
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i__1 = (*n - 1) * *incx + 1; |
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i__2 = *incx; |
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for (ix = 1; i__2 < 0 ? ix >= i__1 : ix <= i__1; ix += i__2) { |
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if (x[ix] != 0.) { |
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absxi = (d__1 = x[ix], abs(d__1)); |
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if (*scale < absxi) { |
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/* Computing 2nd power */ |
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d__1 = *scale / absxi; |
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*sumsq = *sumsq * (d__1 * d__1) + 1; |
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*scale = absxi; |
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} else { |
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/* Computing 2nd power */ |
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d__1 = absxi / *scale; |
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*sumsq += d__1 * d__1; |
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} |
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} |
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/* L10: */ |
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} |
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} |
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return 0; |
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/* End of DLASSQ */ |
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} /* dlassq_ */
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