Hi,
It's me again, I thougth the code would help!!
The coeffients fo C are defined in a main progran that
calls the function STIFFE
REAL FUNCTION STIFFE(NODES, C) RESULT(STIFF)
REAL C(:,:)
REAL NODES(:,:)
DIMENSION STIFF(8,8)
REAL BE(4,8)
REAL JINT(4,4)
REAL J11, J12, J21, J22
REAL MAT(4,8)
REAL XI, ETA
REAL N1, N2, N3,N4
INTEGER I, J, STAGE
MAT=0
B=0
STIFF=0
DO STAGE=1, 4
IF (STAGE .EQ. 1) THEN
XI = -1/3**(.5)
ETA = -1/3**(.5)
END IF
IF (STAGE .EQ. 2) THEN
XI = 1/3**(.5)
ETA = -1/3**(.5)
END IF
IF (STAGE .EQ. 3) THEN
XI = 1/3**(.5)
ETA = 1/3**(.5)
END IF
IF (STAGE .EQ. 4) THEN
XI = -1/3**(.5)
ETA = 1/3**(.5)
END IF
N1 = 1 - XI
N2 = 1 + XI
N3 = 1 - ETA
N4 = 1 + ETA
J11 = 0.25*( -N3*NODES(1,1) + N3*NODES(3,1) +
N4*NODES(5,1) - N4*NODES(7,1) )
J12 = 0.25*( -N1*NODES(1,1) - N2*NODES(3,1) +
N2*NODES(5,1) + N1*NODES(7,1) )
J21 = 0.25*( -N3*NODES(2,1) + N3*NODES(4,1) +
N4*NODES(6,1) - N4*NODES(8,1) )
J22 = 0.25*( -N1*NODES(2,1) - N2*NODES(4,1) +
N2*NODES(6,1) + N1*NODES(8,1) )
DETJ=J11*J22-J12*J21
JINT=0
JINT(1,1) = J22/DETJ
JINT(1,2) = -J21/DETJ
JINT(2,3) = -J12/DETJ
JINT(2,4) = J11/DETJ
JINT(3,1:4) = (/0.0, 0.0, 0.0, 0.0/)
JINT(4,1) = -J12/DETJ
JINT(4,2) = J11/DETJ
JINT(4,3) = J22/DETJ
JINT(4,4) = -J21/DETJ
MAT(1,1:8) = (/-N3, 0.0, N3, 0.0, N4, 0.0, -N4, 0.0/)
MAT(2,1:8) = (/-N1, 0.0, -N2, 0.0, N2, 0.0, N1, 0.0/)
MAT(3,1:8) = (/0.0, -N3, 0.0, N3, 0.0, N4, 0.0, -N4/)
MAT(4,1:8) = (/0.0, -N1, 0.0, -N2, 0.0, N2, 0.0, N1/)
BE=.25*MATMUL(JINT,MAT)
STIFF = MATMUL( MATMUL( TRANSPOSE(BE), C ), BE )*DETJ
+ STIFF
PRINT *,"STIFF"
PRINT '(18X 8EN18.5 )',STIFF
PRINT *,"Checking symmetry"
PRINT '(18X
8F18.2)',STIFF-TRANSPOSE(STIFF)
END DO
END FUNCTION STIFFE
--- miguel jiménez Zapata <smajz2000@xxxxxxxxxxxx>
escribió:
> Hello everybody,
>
> Mi name is Salomon and I'm a fortran user(This
> sounds
> like AA meeting).
> I'm new to the list and to fortran.
> So far I've been able to construct some programs
> with
> succes. However, rigth now I'm facing a problem that
> simply goes far beyond my undestanding.
>
> The problem I'm having is the following
>
> I have a program that has to multiply matrices, one
> of
> the matrices is symmetric and has the form
>
> S = BT.C.B*detj + S
>
> this matrix is in a do loop so it won't be symmetric
> until the end of the cycle. BT is the transpose of B
> and C is a 4*4 matrix. I've been playing with the
> coeffients of C, they are of the order of 1e10. When
> I
> use order of magnitude less than 1e9 the program
> works
> just fine, I get my symmetric matrix, but with
> values
> of 1e10 my result (S) is no longer symmetric. I
> tested
> my code in Matlab and works perfect, it doesnt
> matter
> the order of the coefficents of C.
> I declared C as
> REAL B(4,8)
> REAl S(8,8)
> REAL C(4,4)
> REAL C11,C12,C13,C33,C44
>
> I already tried REAL(4) and REAL(8) and nothing
> happens. I use the gfortran compiler in linux.
> Is there anything I'm missing??
>
> Thanks for your help
>
>
>
>
>
>
___________________________________________________________
>
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> La mejor conexión a Internet y <b >2GB</b> extra a
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>
>
___________________________________________________________
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La mejor conexión a Internet y <b >2GB</b> extra a tu correo por $100 al mes. http://net.yahoo.com.mx
