slassq.c
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00001 /* slassq.f -- translated by f2c (version 20061008).
00002    You must link the resulting object file with libf2c:
00003         on Microsoft Windows system, link with libf2c.lib;
00004         on Linux or Unix systems, link with .../path/to/libf2c.a -lm
00005         or, if you install libf2c.a in a standard place, with -lf2c -lm
00006         -- in that order, at the end of the command line, as in
00007                 cc *.o -lf2c -lm
00008         Source for libf2c is in /netlib/f2c/libf2c.zip, e.g.,
00009 
00010                 http://www.netlib.org/f2c/libf2c.zip
00011 */
00012 
00013 #include "f2c.h"
00014 #include "blaswrap.h"
00015 
00016 /* Subroutine */ int slassq_(integer *n, real *x, integer *incx, real *scale, 
00017         real *sumsq)
00018 {
00019     /* System generated locals */
00020     integer i__1, i__2;
00021     real r__1;
00022 
00023     /* Local variables */
00024     integer ix;
00025     real absxi;
00026 
00027 
00028 /*  -- LAPACK auxiliary routine (version 3.2) -- */
00029 /*     Univ. of Tennessee, Univ. of California Berkeley and NAG Ltd.. */
00030 /*     November 2006 */
00031 
00032 /*     .. Scalar Arguments .. */
00033 /*     .. */
00034 /*     .. Array Arguments .. */
00035 /*     .. */
00036 
00037 /*  Purpose */
00038 /*  ======= */
00039 
00040 /*  SLASSQ  returns the values  scl  and  smsq  such that */
00041 
00042 /*     ( scl**2 )*smsq = x( 1 )**2 +...+ x( n )**2 + ( scale**2 )*sumsq, */
00043 
00044 /*  where  x( i ) = X( 1 + ( i - 1 )*INCX ). The value of  sumsq  is */
00045 /*  assumed to be non-negative and  scl  returns the value */
00046 
00047 /*     scl = max( scale, abs( x( i ) ) ). */
00048 
00049 /*  scale and sumsq must be supplied in SCALE and SUMSQ and */
00050 /*  scl and smsq are overwritten on SCALE and SUMSQ respectively. */
00051 
00052 /*  The routine makes only one pass through the vector x. */
00053 
00054 /*  Arguments */
00055 /*  ========= */
00056 
00057 /*  N       (input) INTEGER */
00058 /*          The number of elements to be used from the vector X. */
00059 
00060 /*  X       (input) REAL array, dimension (N) */
00061 /*          The vector for which a scaled sum of squares is computed. */
00062 /*             x( i )  = X( 1 + ( i - 1 )*INCX ), 1 <= i <= n. */
00063 
00064 /*  INCX    (input) INTEGER */
00065 /*          The increment between successive values of the vector X. */
00066 /*          INCX > 0. */
00067 
00068 /*  SCALE   (input/output) REAL */
00069 /*          On entry, the value  scale  in the equation above. */
00070 /*          On exit, SCALE is overwritten with  scl , the scaling factor */
00071 /*          for the sum of squares. */
00072 
00073 /*  SUMSQ   (input/output) REAL */
00074 /*          On entry, the value  sumsq  in the equation above. */
00075 /*          On exit, SUMSQ is overwritten with  smsq , the basic sum of */
00076 /*          squares from which  scl  has been factored out. */
00077 
00078 /* ===================================================================== */
00079 
00080 /*     .. Parameters .. */
00081 /*     .. */
00082 /*     .. Local Scalars .. */
00083 /*     .. */
00084 /*     .. Intrinsic Functions .. */
00085 /*     .. */
00086 /*     .. Executable Statements .. */
00087 
00088     /* Parameter adjustments */
00089     --x;
00090 
00091     /* Function Body */
00092     if (*n > 0) {
00093         i__1 = (*n - 1) * *incx + 1;
00094         i__2 = *incx;
00095         for (ix = 1; i__2 < 0 ? ix >= i__1 : ix <= i__1; ix += i__2) {
00096             if (x[ix] != 0.f) {
00097                 absxi = (r__1 = x[ix], dabs(r__1));
00098                 if (*scale < absxi) {
00099 /* Computing 2nd power */
00100                     r__1 = *scale / absxi;
00101                     *sumsq = *sumsq * (r__1 * r__1) + 1;
00102                     *scale = absxi;
00103                 } else {
00104 /* Computing 2nd power */
00105                     r__1 = absxi / *scale;
00106                     *sumsq += r__1 * r__1;
00107                 }
00108             }
00109 /* L10: */
00110         }
00111     }
00112     return 0;
00113 
00114 /*     End of SLASSQ */
00115 
00116 } /* slassq_ */


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autogenerated on Sat Jun 8 2019 18:56:11