OpenRadioss 2025.1.11
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PB_Clcm.c
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1/* ---------------------------------------------------------------------
2*
3* -- PBLAS auxiliary routine (version 2.0) --
4* University of Tennessee, Knoxville, Oak Ridge National Laboratory,
5* and University of California, Berkeley.
6* April 1, 1998
7*
8* ---------------------------------------------------------------------
9*/
10/*
11* Include files
12*/
13#include "../pblas.h"
14#include "../PBpblas.h"
15#include "../PBtools.h"
16#include "../PBblacs.h"
17#include "../PBblas.h"
18
19#ifdef __STDC__
20Int PB_Clcm( Int M, Int N )
21#else
22Int PB_Clcm( M, N )
23/*
24* .. Scalar Arguments ..
25*/
26 Int M, N;
27#endif
28{
29/*
30* Purpose
31* =======
32*
33* PB_Clcm computes and returns the Least Common Multiple (LCM) of two
34* positive integers M and N. In fact, the routine computes the Greatest
35* Common Divisor (GCD) and use the property that M*N = GCD*LCM.
36*
37* Arguments
38* =========
39*
40* M (input) INTEGER
41* On entry, M must be at least zero.
42*
43* N (input) INTEGER
44* On entry, N must be at least zero.
45*
46* -- Written on April 1, 1998 by
47* Antoine Petitet, University of Tennessee, Knoxville 37996, USA.
48*
49* ---------------------------------------------------------------------
50*/
51/*
52* .. Local Scalars ..
53*/
54 Int gcd=1, m_val, n_val, t;
55/* ..
56* .. Executable Statements ..
57*
58*/
59 if( M > N ) { m_val = N; n_val = M; }
60 else { m_val = M; n_val = N; }
61
62 while( m_val > 0 )
63 {
64 while( !( m_val & 1 ) )
65 {
66/*
67* m is even
68*/
69 m_val >>= 1;
70/*
71* if n is odd, gcd( m, n ) = gcd( m / 2, n )
72*/
73 if( !( n_val & 1 ) )
74 {
75/*
76* otherwise gcd( m, n ) = 2 * gcd( m / 2, n / 2 )
77*/
78 n_val >>= 1;
79 gcd <<= 1;
80 }
81 }
82/*
83* m is odd now. If n is odd, gcd( m, n ) = gcd( m, ( m - n ) / 2 ).
84* Otherwise, gcd( m, n ) = gcd ( m, n / 2 ).
85*/
86 n_val -= ( n_val & 1 ) ? m_val : 0;
87 n_val >>= 1;
88 while( n_val >= m_val )
89 {
90/*
91* If n is odd, gcd( m, n ) = gcd( m, ( m - n ) / 2 ).
92* Otherwise, gcd( m, n ) = gcd ( m, n / 2 )
93*/
94 n_val -= ( n_val & 1 ) ? m_val : 0;
95 n_val >>= 1;
96 }
97/*
98* n < m, gcd( m, n ) = gcd( n, m )
99*/
100 t = n_val;
101 n_val = m_val;
102 m_val = t;
103 }
104 return ( ( M * N ) / ( n_val * gcd ) );
105/*
106* End of PB_Clcm
107*/
108}
Int
#define Int
Definition Bconfig.h:22
PB_Clcm
Int PB_Clcm()
N
#define N
Definition example_user.c:10