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IRIX Base Documentation 1998 November
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epsilon
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1998-10-30
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84 lines
EPSILON(3I) Last changed: 1-6-98
NNAAMMEE
EEPPSSIILLOONN - Returns a positive number near 1 in the numeric model
SSYYNNOOPPSSIISS
EEPPSSIILLOONN (([XX==]_x))
IIMMPPLLEEMMEENNTTAATTIIOONN
UNICOS, UNICOS/mk, and IRIX systems
SSTTAANNDDAARRDDSS
Fortran 90
DDEESSCCRRIIPPTTIIOONN
The EEPPSSIILLOONN intrinsic function returns a positive model number that is
almost negligible compared to unity in the model representing numbers
of the same type and kind type parameter as the argument. It accepts
the following argument:
_x Must be of type real. It can be scalar or array valued.
EEPPSSIILLOONN is an inquiry function. The name of this intrinsic cannot be
passed as an argument.
RREETTUURRNN VVAALLUUEESS
The result type is a scalar of the same type and kind type parameter
as _x. The result has the value
(1-_p)
_b where _b and _p are as defined in the model for real numbers
representing numbers of the same type and kind type parameter as _x.
For information on the real number model, see the MMOODDEELLSS(3I) man page.
EEXXAAMMPPLLEESS
The following code fragment was run on several systems:
REAL(KIND=4) r4
REAL(KIND=8) r8
REAL(KIND=16) r16
REAL rd
PRINT *,'EPSILON r4=',EPSILON(r4)
PRINT *,'EPSILON r8=',EPSILON(r8)
PRINT *,'EPSILON r16=',EPSILON(r16)
PRINT *,'EPSILON rd=',EPSILON(rd)
END
The results of this test case on IRIX systems are as follows:
EPSILON r4= 1.192092896E-7
EPSILON r8= 2.22044604925031308E-16
EPSILON r16= 1.23259516440783094595582588325435348E-32
EPSILON rd= 1.192092896E-7
The results of this test case on CRAY T90 systems that support IEEE
floating-point arithmetic are as follows:
EPSILON r4= 1.192092896E-7
EPSILON r8= 2.22044604925031308E-16
EPSILON r16= 1.92592994438723585305597794258492732E-34
EPSILON rd= 2.22044604925031308E-16
The results of this test case on UNICOS systems, except for CRAY T90
systems that support IEEE floating-point arithmetic, are as follows:
EPSILON r4= 1.192092895507812E-7
EPSILON r8= 1.4210854715202E-14
EPSILON r16= 5.04870979341447555463506281781E-29
EPSILON rd= 1.4210854715202E-14
The results of this test case on UNICOS/mk systems are as follows:
EPSILON r4= 1.192092896E-7
EPSILON r8= 2.22044604925031308E-16
EPSILON r16= 2.22044604925031308E-16
EPSILON rd= 2.22044604925031308E-16
SSEEEE AALLSSOO
MMOODDEELLSS(3I)
_I_n_t_r_i_n_s_i_c _P_r_o_c_e_d_u_r_e_s _R_e_f_e_r_e_n_c_e _M_a_n_u_a_l, publication SR-2138, for the
printed version of this man page.