[英]R language source code - what is `NOMORE_FOR_THREADS` in the C code
我正在瀏覽函數gamma()
的R源代碼,該函數指向此C源文件 。
代碼片段如下:
#ifdef NOMORE_FOR_THREADS
static int ngam = 0;
static double xmin = 0, xmax = 0., xsml = 0., dxrel = 0.;
/* Initialize machine dependent constants, the first time gamma() is called.
FIXME for threads ! */
if (ngam == 0) {
ngam = chebyshev_init(gamcs, 42, DBL_EPSILON/20);/*was .1*d1mach(3)*/
gammalims(&xmin, &xmax);/*-> ./gammalims.c */
xsml = exp(fmax2(log(DBL_MIN), -log(DBL_MAX)) + 0.01);
/* = exp(.01)*DBL_MIN = 2.247e-308 for IEEE */
dxrel = sqrt(DBL_EPSILON);/*was sqrt(d1mach(4)) */
}
#else
/* For IEEE double precision DBL_EPSILON = 2^-52 = 2.220446049250313e-16 :
* (xmin, xmax) are non-trivial, see ./gammalims.c
* xsml = exp(.01)*DBL_MIN
* dxrel = sqrt(DBL_EPSILON) = 2 ^ -26
*/
# define ngam 22
# define xmin -170.5674972726612
# define xmax 171.61447887182298
# define xsml 2.2474362225598545e-308
# define dxrel 1.490116119384765696e-8
#endif
現在我明白這段代碼正在初始化變量的值,如ngam
, xsml
, dxrel
等。但我不明白什么是NOMORE_FOR_THREADS
。
我無法找到定義的位置,所以我很困惑它何時進入#ifdef
子句,或者只是進入#else
子句並根據IEEE標准定義變量。
如果有人能夠了解NOMORE_FOR_THREADS
或它的定義,那將會非常有幫助。
謝謝您的幫助。
看起來在版本13433中添加了#ifdef
:
> svn log -vr13433
------------------------------------------------------------------------
r13433 | maechler | 2001-04-10 10:05:54 -0500 (Tue, 10 Apr 2001) | 2 lines
Changed paths:
M /trunk/src/nmath/beta.c
M /trunk/src/nmath/gamma.c
M /trunk/src/nmath/lgamma.c
M /trunk/src/nmath/lgammacor.c
globals now #ifdef NOMORE_FOR_THREADS
------------------------------------------------------------------------
這是前一版本的差異:
> svn diff -r13432:13433 src/nmath/gamma.c
Index: src/nmath/gamma.c
===================================================================
--- src/nmath/gamma.c (revision 13432)
+++ src/nmath/gamma.c (revision 13433)
@@ -1,7 +1,7 @@
/*
* Mathlib : A C Library of Special Functions
* Copyright (C) 1998 Ross Ihaka
- * Copyright (C) 2000 The R Development Core Team
+ * Copyright (C) 2000-2001 The R Development Core Team
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@@ -40,7 +40,7 @@
double gammafn(double x)
{
- static /* const */ double gamcs[42] = {
+ const double gamcs[42] = {
+.8571195590989331421920062399942e-2,
+.4415381324841006757191315771652e-2,
+.5685043681599363378632664588789e-1,
@@ -89,6 +89,7 @@
double y;
double sinpiy, value;
+#ifdef NOMORE_FOR_THREADS
static int ngam = 0;
static double xmin = 0, xmax = 0., xsml = 0., dxrel = 0.;
@@ -101,6 +102,18 @@
/* = exp(.01)*DBL_MIN = 2.247e-308 for IEEE */
dxrel = sqrt(1/DBL_EPSILON);/*was (1/d1mach(4)) */
}
+#else
+/* For IEEE double precision DBL_EPSILON = 2^-52 = 2.220446049250313e-16 :
+ * (xmin, xmax) are non-trivial, see ./gammalims.c
+ * xsml = exp(.01)*DBL_MIN
+ * dxrel = sqrt(1/DBL_EPSILON) = 2 ^ 26
+*/
+# define ngam 22
+# define xmin -170.5674972726612
+# define xmax 171.61447887182298
+# define xsml 2.2474362225598545e-308
+# define dxrel 67108864.
+#endif
if(ISNAN(x)) return x;
我沒有看到NOMORE_FOR_THREADS
在該版本的源代碼中的任何位置定義,在添加它之后的下幾百個版本中,或者在當前版本中。 它可能(雖然似乎不太可能)可以在某些系統頭文件中定義。 它似乎更有可能通過命令行參數指定。
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