glenn@suphys.physics.su.OZ.AU (08/28/90)
Hi,
I'm trying to write a program which uses a 2-d array of structs to
represent a matrix of complex numbers: struct complex {double r; double i}.
The array is dynamically allocated as it can become rather large. I don't
want to do complex arithmetic in C (we don't have C++ :-)) so I thought I'd
use Fortran.
Problem: How does one pass a 2-d C array of structs to a Fortran subroutine?
I've managed to do it with a 1-d array, but our Manuals (SUN OS 4.1) say
nothing about 2-d arrays; that part seems to just be a copy (with minor changes)
of the version 7 UNIX manual.
Any example programs or pointers to good cross language references would be much
appreciated.
BTW I'm using f77 and cc (standard SUN C compiler).
Thanks in advance,
Glenn
glenn@qed.physics.su.oz.au
--
Glenn Geers | "So when it's over, we're back to people.
Department of Theoretical Physics | Just to prove that human touch can have
The University of Sydney | no equal."
Sydney NSW 2006 Australia | - Basia Trzetrzelewska, 'Prime Time TV'tsaiwn@eecs.nwu.edu (Wen-Nung Tsai) (08/31/90)
In <1990Aug27.220828.9319@metro.ucc.su.OZ.AU> glenn@qed.physics.su.oz.au writes: > I'm trying to write a program which uses a 2-d array of structs to >represent a matrix of complex numbers: struct complex {double r; double i}. >The array is dynamically allocated as it can become rather large. I don't > want to do complex arithmetic in C (we don't have C++ :-)) so I thought I'd > use Fortran. > > Problem: How does one pass a 2-d C array of structs to a Fortran subroutine? > > I've managed to do it with a 1-d array, but our Manuals (SUN OS 4.1) say > nothing about 2-d arrays; that part seems to just be a copy (with minor changes) > of the version 7 UNIX manual. > ... > Glenn Since you already knew how to do it in one-d array, you can use the same FORTRAN routine you have written if you want to apply the operation to all elements of the 2-d array. I.e., pass the address of the 2-d C array and the total-no-of-elements to your FORTRAN routine which treats it as 1-d array. For example, assume your FORTRAN routine looks like: subroutine add(aa,bb,n) complex aa(n), bb(n) ... And your C program contains: complex a1[3][5], a2[3][5]; /* you already defined STRUCT complex */ int tot_ele; Then, you can call "add" in this way: tot_ele=15; /* 3*5=15 */ add(a1,a2,&tot_ele) NOTE the "&" sign! You can not say add(a1,a2,15), this is because : IN FORTRAN, parameters are always passed by REFERENCE. Thus, the variable "tot_ele" is necessary. IF you insist to do it in 2-d array,(for example, you want to do matrix operations in FORTRAN routine), it's not difficult: IN C: ... #define CN1 5 #define CN2 3 #define CN3 7 complex a1[CN1][CN2], a2[CN3][CN1]; complex a3[CN3][CN2]; int n1,n2,n3; ... n1=CN1; n2=CN2; n3=CN3; doit(a1,a2,a3,&n1,&n2,&n3) ... In FORTRAN: subroutine doit(aa,bb,cc,n1,n2,n3) complex aa(n2,n1), bb(n1,1), cc(n2,*) Comm aa is (n2,n1), bb is (n1,n3), cc is (n2,n3) .... NOTE the a1[5][3] in C maps to aa(3,5) in FORTRAN routine, this is because: Array in C is arranged in row-major. But array in FORTRAN is column-major. I.e., aa(1,1) is a1[0][0]; aa(2,1) is a1[0][1]; aa(3,1) is a1[0][2]; aa(1,2) is a1[1][0];..... ................aa(i,k) is a1[k-1][i-1] This allows the "aa" can be declared as aa(n2,*) or even aa(n2,1) in FORTRAN. If it's a 3-d array, say c1[n1][n2][n3], it can be mapped to FORTRAN routine as c1(n3,n2,n1) and the declaration in FORTRAN looks like: subroutine easy(c1,n1,n2,n3) complex c1(n3,n2,*) (The last dimension of dummy(parameter) array always doesn't affect the result. So, you can declared it as any one of the following: complex c1(n3,n2,*) complex c1(n3,n2,1) complex c1(n3,n2,2) ... complex c1(n3,n2,999) ... complex c1(n3,n2,n1) ===========================Hope this can help you. Wen-Nung ============================= Wen-Nung Tsai ============================= tsaiwn@eecs.nwu.edu "Man invented language to satisfy his deep need to complain." -- Lily Tomlin =========================================================================