1-11 FORTRAN/C INTEROPERABILITY
********************************
(Thanks to Craig Burley for the comments)
(partially based on the Fortran FAQ)
FORTRAN is well suited to numerical computations, C is suitable for
system programming tasks. A combination of the two languages in one
program should have been the best solution for some programs.
It seems simple enough, we can easily create object modules from both
FORTRAN and C code, the object modules will be surely compatible if
made with the native compilers, then we can link edit them together.
Unfortunately some issues make this seemingly simple interfacing
highly platform dependent.
Note that for some systems, you have to initialize a runtime system
(shared libraries) explicitly if you call a different language,
and stopping execution from the other program may not work properly.
Cfortran package
----------------
One solution is to use the amazing 'cfortran' package, an include
file that performs the interfacing using the C language preprocessor.
It takes some time to study the documentation, and it may overtax
the preprocessor.
The cfortran package makes Fortran/C interfacing quick and easy
for a wide range of platforms. The most recent version of the
include file "cfortran.h", and the documentation is available
via anonymous ftp from:
ftp://zebra.desy.de/cfortran
and via www at http://www-zeus.desy.de/~burow .
Manual interfacing
------------------
If you prefer to do it manually, look first in your COMPILER
DOCUMENTATION, Sun and IRIX have a lot to say on this subject.
A multi-platform (with some minor changes) example can be found in
the chapter on "variable size arrays".
There are some general issues you must be aware of before starting
such work:
Routines names
--------------
On some machines (e.g. UNIX) the FORTRAN compiler appends a trailing
underscore to FORTRAN routine names, both in subroutine/function
definitions and when calling them.
Why add the underscore suffix? Possible explanations are:
o Prevent name clashes of user-written routines with the
routines in the system libraries used by the compiler
at link time (the routine names in these libraries
usually don't have a trailing underscore).
For example, UNIX system routines may have simple names,
that may be used in a user program.
o Prevent "amateurish" mixed-language programming.
Without proper understanding these attempts may produce
erroneous results.
In mixed-language programs on such machines, the linker will have a
problem when trying to match routine calls and routine code in the
object code.
Either the FORTRAN CALL statement (with underscores appended) will
reference a non-FORTRAN routine, or the other language may call a
FORTRAN routine (also with underscores appended). In each case
there will be a mismatch, which can be avoided by manually
supplying the required underscores:
o If a FORTRAN routine calls a routine written another
language, append a trailing underscore IN THE DEFINITION
(in the code) of the non-FORTRAN routine.
o If a non-FORTRAN routine calls a FORTRAN routine,
append an underscore in THE CALLING STATEMENT to
the FORTRAN routine name.
Compilers which behave like that may transform external user-defined
names in the following way:
Appends a trailing underscore Name remains unaffected
----------------------------- -----------------------
Main program name Blank COMMON name '_BLNK__'
Named COMMON blocks Intrinsic functions names
BLOCKDATA subprograms
All names implicitly or
explicitly declared EXTERNAL
Check your compiler documentation, you may not have to add anything,
if your compiler/linker does it another way.
For example, VMS differentiates between user and system defined names
by having the later contain a '$' sign, users are advised not to use
that sign in names.
There may be a similar problem if the compiler/linker changes the case
of routine names (e.g. CRAY uppercasing).
CALLING C ROUTINES FROM FORTRAN
===============================
Machine C Routine name
------- ------------------
ALPHA/DUNIX lowercase letters_ (default)
ALPHA/VMS anything
CRAY UPPERCASE LETTERS
HP lowercase letters (?)
IBM/AIX lowercase letters (all IBM's ?)
SGI/IRIX lowercase letters_
SUN lowercase letters_
TITAN UPPERCASE LETTERS
VAX/VMS anything
VAX/ULTRIX lowercase letters_ (default)
Variable passing mechanisms
---------------------------
Fortran usually passes its variables by reference (passes pointers).
That means that you MUST give addresses in your calling C-program.
Function results, may be passed by value, for example, the following
code calls a FORTRAN function called "gamma":
double x, y;
..................
x = 2.0;
y = gamma_(&x)
Array storage order
-------------------
Fortran uses a column wise storage of matrices while C stores them
row wise. This means that when you want to pass a matrix from your
C-program to the fortran routine you must transpose the matrix
in your program before entering the routine. Of course, any output
from such a routine must be transposed again.
If you omit this step, then probably your program will run (because
it has data to compute on) but it will generate wrong answers.
Transposition is expensive, you may avoid it by adapting the source
code, when the FORTRAN source says A(j+1,i+1) it could mean a[i][j] in C,.
There are times when you don't want to modify already existing FORTRAN
and C code, in such cases you may have to write a transposition wrapper.
This can be advisable for reasons of clarity (i.e. keeping the
documentation the code and the math in sync.)
Array indexes
-------------
Remember that array indexes in Fortran starts by default at 1 while
in C they start at index 0; hence a passed array fortran_array[1:100]
must be used in the C-routine/program as c_array[0:99].
Variable type matching
----------------------
Watch out especially with float's and double's. Make sure that the
size of the variable in the calling program is identical to the size
in the Fortran routine:
float --- REAL (this is typical, but not always the case)
double --- REAL*8
Character strings
-----------------
FORTRAN may pass string lengths BY VALUE in the order the strings appear
in the argument list. These will NOT appear in the FORTRAN argument list,
but will appear in the C argument list.
You will need to take care of nulls and blanks spaces explicitly if you
ignore this ...
Some untested advice
--------------------
If you have the Fortran source code (of any routine) then on some
platforms you may use compiler directives specifying that the
Fortran compiler should use row wise storage. Some platforms support
these directives. However watch out with this if you call the same
routine from another Fortran routine/program.
Matching float types is extremely important on machines with little-
endian byte ordering. Parsing a float (C-routine) to a real*8 (Fortran)
number will not generate SEGV (SEGmentation Violation error) but give
wrong results as the data is parsed wrongly.
Mixing I/O on the same file descriptors may be problematic.
If you do ANY I/O in FORTRAN, you may have to use a FORTRAN main program.
The Sun FORTRAN compiler used lex and yacc to do the conversion of a
run time format from a character variable. If you use lex and yacc,
either rename the variables and functions or partially link before
you link to the FORTRAN libraries.
An example environment: the VMS Common Language Environment
-----------------------------------------------------------
VMS argument passing mechanisms are standardized by the VAX/ALPHA
procedure-calling standards, and inter-language calls are made simple,
a few FORTRAN language extensions makes it even simpler.
FORTRAN programs can use the 'builtin functions' to pass arguments
to C routines:
%REF(argument) Makes the argument pass by reference,
this is the default for numeric types.
Useful for strings!
%VAL(argument) Makes the argument pass by value.
Useful for numeric types!
program pssarg
integer int
character string*10
int = 8
string = 'apples'
call cstring(%val(int), %ref(string // char(0)))
end
#include
void cstring(int num, char *string)
{
printf(" %d %s\n", num, string);
return;
}
Another (but ugly) workaround for the FORTRAN/C string-passing
problem is to store the strings in BYTE arrays.
To go a little deeper, the only technical detail you have to learn
is the structure of the fixed-length string descriptor used to pass
character data:
struct descriptor /* VMS fixed length string */
{ /* descriptor used in FORTRAN */
unsigned short length;
unsigned char data_type, /* = 14 */
dsc_class; /* = 1 */
char *string_ptr;
};
Fortran compilers on UNIX machines don't use descriptors, instead a
"hidden" integer argument is added to the end of the argument list,
specifying the length of the string.
Two VMS examples that pass an INTEGER and a CHARACTER*10 string between
FORTRAN and C follow. All inter-language complications were 'pushed' to
the C code, the FORTRAN code is not 'aware' of them.
The hardcoding of descriptor.data_type and descriptor.dsc_class values
is of course bad programming practice. The proper header file (descrip.h)
should have been included and used.
The dimensional information of the CHARACTER*10 is contained in the
descriptor, so in the argument list you have to pass only the address
of the descriptor.
A VMS example (FORTRAN calling C)
---------------------------------
program for2c
integer n
character string*10
n = 123
string = 'abcdefghij'
write(*,*) ' In fortran: n= ', n
write(*,*) ' In fortran: string= ', string
call c_routine(n, string)
end
#include <stdio.h>
struct descriptor /* VMS fixed length string */
{ /* descriptor used in FORTRAN */
unsigned short length;
unsigned char data_type, /* = 14 */
dsc_class; /* = 1 */
char *string_ptr;
};
c_routine(int *n, struct descriptor *dsc)
{
int len;
char *string;
printf(" in C: n= %d \n", *n);
len = dsc->length;
printf(" in C: len= %d \n", len);
string = dsc->string_ptr;
printf(" in C: string= %*.*s \n", len, len, string);
return;
}
Another VMS example (C calling FORTRAN)
---------------------------------------
#include <stdio.h>
#include <string.h>
struct descriptor /* VMS fixed length string */
{ /* descriptor used in FORTRAN */
unsigned short length;
unsigned char data_type, /* = 14 */
dsc_class; /* = 1 */
char *string_ptr;
};
void f_routine(int *, struct descriptor *);
main()
{
int n = 123;
char string[] = "abcdefghij";
static struct descriptor dsc;
printf(" in C: n= %d \n", n);
printf(" in C: string= %s \n", string);
dsc.length = strlen(string);
dsc.data_type = 14;
dsc.dsc_class = 1;
dsc.string_ptr = string;
f_routine(&n, &dsc);
}
subroutine f_routine (n, string)
integer n
character string*(*)
write(*,*) ' In fortran: n= ', n
write(*,*) ' In fortran: string= ', string
return
end
A much more important factor in the social movement than those already mentioned was the ever-increasing influence of women. This probably stood at the lowest point to which it has ever fallen, during the classic age of Greek life and thought. In the history of Thucydides, so far as it forms a connected series of events, four times only during a period of nearly seventy years does a woman cross the scene. In each instance her apparition only lasts for a moment. In three of the four instances she is a queen or a princess, and belongs either to the half-barbarous kingdoms of northern Hellas or to wholly barbarous Thrace. In the one remaining instance208— that of the woman who helps some of the trapped Thebans to make their escape from Plataea—while her deed of mercy will live for ever, her name is for ever lost.319 But no sooner did philosophy abandon physics for ethics and religion than the importance of those subjects to women was perceived, first by Socrates, and after him by Xenophon and Plato. Women are said to have attended Plato’s lectures disguised as men. Women formed part of the circle which gathered round Epicurus in his suburban retreat. Others aspired not only to learn but to teach. Arêtê, the daughter of Aristippus, handed on the Cyrenaic doctrine to her son, the younger Aristippus. Hipparchia, the wife of Crates the Cynic, earned a place among the representatives of his school. But all these were exceptions; some of them belonged to the class of Hetaerae; and philosophy, although it might address itself to them, remained unaffected by their influence. The case was widely different in Rome, where women were far more highly honoured than in Greece;320 and even if the prominent part assigned to them in the legendary history of the city be a proof, among others, of its untrustworthiness, still that such stories should be thought worth inventing and preserving is an indirect proof of the extent to which feminine influence prevailed. With the loss of political liberty, their importance, as always happens at such a conjuncture, was considerably increased. Under a personal government there is far more scope for intrigue than where law is king; and as intriguers women are at least the209 equals of men. Moreover, they profited fully by the levelling tendencies of the age. One great service of the imperial jurisconsults was to remove some of the disabilities under which women formerly suffered. According to the old law, they were placed under male guardianship through their whole life, but this restraint was first reduced to a legal fiction by compelling the guardian to do what they wished, and at last it was entirely abolished. Their powers both of inheritance and bequest were extended; they frequently possessed immense wealth; and their wealth was sometimes expended for purposes of public munificence. Their social freedom seems to have been unlimited, and they formed combinations among themselves which probably served to increase their general influence.321 The old religions of Greece and Italy were essentially oracular. While inculcating the existence of supernatural beings, and prescribing the modes according to which such beings were to be worshipped, they paid most attention to the interpretation of the signs by which either future events in general, or the consequences of particular actions, were supposed to be divinely revealed. Of these intimations, some were given to the whole world, so that he who ran might read, others were reserved for certain favoured localities, and only communicated through the appointed ministers of the god. The Delphic oracle in particular enjoyed an enormous reputation both among Greeks and barbarians for guidance afforded under the latter conditions; and during a considerable period it may even be said to have directed the course of Hellenic civilisation. It was also under this form that supernatural religion suffered most injury from the great intellectual movement which followed the Persian wars. Men who had learned to study the constant sequences of Nature for themselves, and to shape their conduct according to fixed principles of prudence or of justice, either thought it irreverent to trouble the god about questions on which they were competent to form an opinion for themselves, or did not choose to place a well-considered scheme at the mercy of his possibly interested responses. That such a revolution occurred about the middle of the fifth century B.C., seems proved by the great change of tone in reference to this subject which one perceives on passing from Aeschylus to Sophocles. That anyone should question the veracity of an oracle is a supposition which never crosses the mind of the elder dramatist. A knowledge of augury counts among the greatest benefits222 conferred by Prometheus on mankind, and the Titan brings Zeus himself to terms by his acquaintance with the secrets of destiny. Sophocles, on the other hand, evidently has to deal with a sceptical generation, despising prophecies and needing to be warned of the fearful consequences brought about by neglecting their injunctions. The stranger had a pleasant, round face, with eyes that twinkled in spite of the creases around them that showed worry. No wonder he was worried, Sandy thought: having deserted the craft they had foiled in its attempt to get the gems, the man had returned from some short foray to discover his craft replaced by another. “Thanks,” Dick retorted, without smiling. When they reached him, in the dying glow of the flashlight Dick trained on a body lying in a heap, they identified the man who had been warned by his gypsy fortune teller to “look out for a hidden enemy.” He was lying at full length in the mould and leaves. "But that is sport," she answered carelessly. On the retirement of Townshend, Walpole reigned supreme and without a rival in the Cabinet. Henry Pelham was made Secretary at War; Compton Earl of Wilmington Privy Seal. He left foreign affairs chiefly to Stanhope, now Lord Harrington, and to the Duke of Newcastle, impressing on them by all means to avoid quarrels with foreign Powers, and maintain the blessings of peace. With all the faults of Walpole, this was the praise of his political system, which system, on the meeting of Parliament in the spring of 1731, was violently attacked by Wyndham and Pulteney, on the plea that we were making ruinous treaties, and sacrificing British interests, in order to benefit Hanover, the eternal millstone round the neck of England. Pulteney and Bolingbroke carried the same attack into the pages of The Craftsman, but they failed to move Walpole, or to shake his power. The English Government, instead of treating Wilkes with a dignified indifference, was weak enough to show how deeply it was touched by him, dismissed him from his commission of Colonel of the Buckinghamshire Militia, and treated Lord Temple as an abettor of his, by depriving him of the Lord-Lieutenancy of the same county, and striking his name from the list of Privy Councillors, giving the Lord-Lieutenancy to Dashwood, now Lord Le Despencer. "I tell you what I'll do," said the Deacon, after a little consideration. "I feel as if both Si and you kin stand a little more'n you had yesterday. I'll cook two to-day. We'll send a big cupful over to Capt. McGillicuddy. That'll leave us two for to-morrer. After that we'll have to trust to Providence." "Indeed you won't," said the Surgeon decisively. "You'll go straight home, and stay there until you are well. You won't be fit for duty for at least a month yet, if then. If you went out into camp now you would have a relapse, and be dead inside of a week. The country between here and Chattanooga is dotted with the graves of men who have been sent back to the front too soon." "Adone do wud that—though you sound more as if you wur in a black temper wud me than as if you pitied me." "Wot about this gal he's married?" "Don't come any further." "Davy, it 'ud be cruel of us to go and leave him." "Insolent priest!" interrupted De Boteler, "do you dare to justify what you have done? Now, by my faith, if you had with proper humility acknowledged your fault and sued for pardon—pardon you should have had. But now, you leave this castle instantly. I will teach you that De Boteler will yet be master of his own house, and his own vassals. And here I swear (and the baron of Sudley uttered an imprecation) that, for your meddling knavery, no priest or monk shall ever again abide here. If the varlets want to shrieve, they can go to the Abbey; and if they want to hear mass, a priest can come from Winchcombe. But never shall another of your meddling fraternity abide at Sudley while Roland de Boteler is its lord." "My lord," said Edith, in her defence, "this woman has sworn falsely. The medicine I gave was a sovereign remedy, if given as I ordered. Ten drops would have saved the child's life; but the contents of the phial destroyed it. The words I uttered were prayers for the life of the child. My children, and all who know me, can bear witness that I have a custom of asking His blessing upon all I take in hand. I raised my eyes towards heaven, and muttered words; but, my lord, they were words of prayer—and I looked up as I prayed, to the footstool of the Lord. But it is in vain to contend: the malice of the wicked will triumph, and Edith Holgrave, who even in thought never harmed one of God's creatures, must be sacrificed to cover the guilt, or hide the thoughtlessness of another." "Aye, Sir Treasurer, thou hast reason to sink thy head! Thy odious poll-tax has mingled vengeance—nay, blood—with the cry of the bond." HoME古一级毛片免费观看
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