Doxygen Source Code Documentation
eis_epslon.c File Reference
#include "f2c.h"Go to the source code of this file.
Functions | |
| doublereal | epslon_ (doublereal *x) |
Function Documentation
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Definition at line 8 of file eis_epslon.c. Referenced by bandv_(), bisect_(), cinvit_(), invit_(), qzit_(), ratqr_(), tinvit_(), tqlrat_(), tridib_(), and tsturm_().
00009 {
00010 /* System generated locals */
00011 doublereal ret_val, d__1;
00012
00013 /* Local variables */
00014 static doublereal a, b, c__, eps;
00015
00016
00017 /* ESTIMATE UNIT ROUNDOFF IN QUANTITIES OF SIZE X. */
00018
00019
00020 /* THIS PROGRAM SHOULD FUNCTION PROPERLY ON ALL SYSTEMS */
00021 /* SATISFYING THE FOLLOWING TWO ASSUMPTIONS, */
00022 /* 1. THE BASE USED IN REPRESENTING FLOATING POINT */
00023 /* NUMBERS IS NOT A POWER OF THREE. */
00024 /* 2. THE QUANTITY A IN STATEMENT 10 IS REPRESENTED TO */
00025 /* THE ACCURACY USED IN FLOATING POINT VARIABLES */
00026 /* THAT ARE STORED IN MEMORY. */
00027 /* THE STATEMENT NUMBER 10 AND THE GO TO 10 ARE INTENDED TO */
00028 /* FORCE OPTIMIZING COMPILERS TO GENERATE CODE SATISFYING */
00029 /* ASSUMPTION 2. */
00030 /* UNDER THESE ASSUMPTIONS, IT SHOULD BE TRUE THAT, */
00031 /* A IS NOT EXACTLY EQUAL TO FOUR-THIRDS, */
00032 /* B HAS A ZERO FOR ITS LAST BIT OR DIGIT, */
00033 /* C IS NOT EXACTLY EQUAL TO ONE, */
00034 /* EPS MEASURES THE SEPARATION OF 1.0 FROM */
00035 /* THE NEXT LARGER FLOATING POINT NUMBER. */
00036 /* THE DEVELOPERS OF EISPACK WOULD APPRECIATE BEING INFORMED */
00037 /* ABOUT ANY SYSTEMS WHERE THESE ASSUMPTIONS DO NOT HOLD. */
00038
00039 /* THIS VERSION DATED 4/6/83. */
00040
00041 a = 1.3333333333333333;
00042 L10:
00043 b = a - 1.;
00044 c__ = b + b + b;
00045 eps = (d__1 = c__ - 1., abs(d__1));
00046 if (eps == 0.) {
00047 goto L10;
00048 }
00049 ret_val = eps * abs(*x);
00050 return ret_val;
00051 } /* epslon_ */
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