fortran workshop

8/10/2019 Fortran Workshop

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Fortran 90+IntensiveWorkshopDr Stephen So

([email protected])

Griffith Schoo of !ngineering
mailto:[email protected]:[email protected]


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http://maxwell.me.gu.edu.au/sso/fortran

"rief #utine Fortran versus $%&'%"

Fortran progra* deveop*ent and snta,

Intrinsic data tpes and operators

%rras and arra *anipuation Fie reading and -riting

Suprogra*s / functions and suroutines

$odues

Derived data tpes Function and operating overoading

gfortran co*pier opti*isation

aing '%%1 and FF&%1

aing Fortran 90 suprogra*s fro* $%&'%"
http://maxwell.me.gu.edu.au/sso/fortranhttp://maxwell.me.gu.edu.au/sso/fortran


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Introduction !ssentia ee*ents of the Fortran 90+

(90923004) progra**ing anguage -i e

covered rior progra**ing e,perience (e.g. $%&'%")

is assu*ed

Working in the Windo-s environ*ent

See http5*a,-e.*e.gu.edu.aussofortran
http://maxwell.me.gu.edu.au/sso/fortranhttp://maxwell.me.gu.edu.au/sso/fortranhttp://maxwell.me.gu.edu.au/sso/fortranhttp://maxwell.me.gu.edu.au/sso/fortran


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What do I need in order to-rite Fortran progra*s6 Fortran co*pier converts our source coded into an e,ecutae

proe*

&e,t editor or integrated deveop*entenviron*ent (ID!) used to -rite our source code into a te,t fie

So*e nu*erica iraries ('%%17 "'%S7FF&%17 81SI&!7 etc.) contains suprogra*s -ritten (and tested)

others


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Fortran co*piers&here are *an co**ercia Fortran co*piers on

the *arket (cost a ot of :::)

Inte ;isua Fortran GI ;isua Fortran


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ID!s o**ercia ID!s $icrosoft ;isua Studio (used Inte ;F7 GI

;F7 'ahe7 o*pa= ;F) usto* ID!s (used %soft and oder version

of 'ahe Fortran 92)

Free and open>source ID!s

ode"ocks !cipse (hotran pugin)


7/145http://maxwell.me.gu.edu.au/sso/fortran



Fortran versus $%&'%" I"$ $athe*atica For*ua &ransation Sste*

(Fortran II7 III7 I;7 ??7 7 907 927 30047 300A)

%dvantages5 ;er fast (co*pied versus interpreted)

!fficient -ith *e*or (can deaocate arras)

$ore contro over data representation and

for*atting ;er popuar in scientific and engineering

co**unit

'ots of egac Fortran code avaiae ("'%S7

'%%17 etc.)



Fortran versus $%&'%" Disadvantages5&edious and difficut to earn

$ore verose

;er i*ited *atri, *anipuation in routines or tooo,es

in visuaisation toos



Fortran versus strengths are in sste*s progra**ing

FortranBs strengths are in nu*er crunchingand nu*erica data processing

Fortran co*piers are *ore sophisticatedthan co*piers for nu*erica opti*isation

$odern Fortran co*piers have support forparae processing and G processing(D%) as -e



o*piing and inking Fortran 90 source code is tped into a te,t

fie ( C.f907 C.92)

&o run the Fortran progra*5 Step 5 o*piesource code E oect fie

(C.o) Step 35 'inkin other oect fies (other

suprogra*s) and stu E e,ecutae fie(C.e,e)



o*piing and inking

Compilationstage

Linkingstage

main.f90

program.exe

Windows stub

Static library

func2.o

func1.o

main.o

func2.f90

func1.f90



sing gfortran (fro*co**and>ine) In a co**and ine7 to co*pie and ink a

singe Fortran source fie (heo.f90) gfortran heo.f90 >o heo.e,e

&o perfor* co*piing on (no inking) gfortran heo.f90 >c

&o ink *utipe oect fies gfortran heo.o func.o func3.o >o heo.e,e

&o incude static iraries gfortran heo.o iapack.a ias.a >o heo.e,e



Fortran progra* structure

programprogram_name

specification statements

executable statements

[contains]

[internal subprograms]

end programprogram_name



Si*pe Fortran progra*

programhello

implicit none

! This is a comment

print*, 'Hello, world'

end programhello

Save this into a te,t fie caed heo.f90

o*pie in co**and ine gfortran heo.f90 >o heo.e,e

his statement should always beincluded



o**ents and continuation %n ine of code after J is treated as a

co**ent

% state*ent can e roken into *utipeines appending a K (in $%&'%" it is ...)print*, 'Length of the two sides are', &

side_1, 'and', side_2, &

'metres'$utipe state*ents can e put onto a singe

ine separating the* -ith se*i>coons (L)

side_1 = 3; side_2 = 4; h!ot = 1"



rinting to the screenWe can see the print state*ent ao-s us to

dispa te,t on the screen

Snta,5 printfmt, list

fmtspecifies ho- the te,t is to e for*atted(*ore aout this ater)

If fmtis an asterisk (C)7 for*atting isauto*atic (ist>directed I#)

list can consist of strings (te,t) or variaes



8eading fro* keoard&o read data fro* the keoard7 -e use the

readstate*ent

Snta,5readfmt7 list

If fmtis an asterisk (C)7 the for*at of inputdata is auto*atic

list consists of variaes to store the data



;ariaes 'ike $%&'%"7 variaes are *e*or

ocations used to store data

nike $%&'%"5 -e *ust decare every variablethat -e use

in the progra*(unike $%&'%") ;ariae na*es are not case>sensitive (e.g. pi7

pI7 i7 I are the sa*e na*e) Snta, for decaring variaes data_type[, specifiers##] variable_name



!,a*pes of variaedecarations integer## $o%nter, i, real## mass real, parameter## !i = 3141( logical## flag = .false. complex## im!edan$e

character)2" ## name


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Intrinsic nu*eric tpes Integer (M tes 43 its) % -hoe nu*er that has no fractiona part or

deci*a point e.g. 47 >MM7 30 'argest5 3MMA4?M

Real (M tes 43 its) % nu*er that can have a fractiona part or deci*a

point e.g. 4.07 3.4M7 >9A.37 4.4eA I!!! 2M singe precision5 ? deci*a digits

S*aest7 'argest5 .2M9M42!>4A7 4.M03A34M!+4A


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Intrinsic nu*eric tpesDouble precision(A tes ?M its) % rea nu*er -ith t-ice the precision e.g. 4.4dA

I!!! 2M doue precision5 2 deci*a digits

S*aest5 3.33204A2A20304A!>40A 'argest5 .9?944MA?342!+40A

Complex

o*pe, nu*er consisting of a rea part andi*aginar part

e.g. 4.3 / M.9A i E (4.37 M.9A)


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Intrinsic non>nu*eric tpesCharacter %SII character or te,t e.g. BaB7 BtB7 B:B character(N) to decare string of Nchars an use either N or B to dei*it strings for concatenation e.g. BacBBdefB

len() function returns the nu*er ofcharacters

Logical !ither .true.or .false.


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1ind para*eter&he range of an integer (*a, 3MMA4?M)

*a not e enough

&he precision of doue precision (2) *anot e enough

Fortran 90 ao-s us to specif the kind ofinteger and the kind of rea

&he kind nu*er is usually(ut not a-as)the nu*er of tesinteger(kindE A) or integer(A) / A te integer

real(A) / A te rea (doue precision)


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1inds for different co*piers o*pier specific (refer to kinds.f90 and

kindfind.f90)

gfortran supports5

integer()7 integer(3)7 integer(M)7 integer(A)7integer(?) (?M it on)

rea(M)7 rea(A) (doue precision)7

rea(0) / precision of A (e,tended precision)

'ahe Fortran 92 and Inte ;isua Fortransupports5 integer()7 integer(3)7 integer(M)7 integer(A)

rea(M)7 rea(A) (doue precision)7

rea(?) / precision of 44 (=uad precision)


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Intrinsic kind functions kind(a) -i return the kind of variae a

se the foo-ing functions for portaiit

(since the kind nu*er *a not e e=ua tothe nu*er of tes)5selected_int_kind(p) returns the kind of

integer -ithpsignificant digits

selected_real_kind(p7 r) returns the kindnu*er of a rea -ith p digit precision anddeci*a e,ponent range of >rand +r

&hese functions return > if not supported the co*pier7 generating a co*pie error


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Specifing the kind of iteraconstant In order to specif the kind for a itera

constant7 -e use an underscore foo-ed

the kind nu*er 34O3 / integer(3) itera constant

34.4OA / rea(A) itera constant

$ore convenient to use para*etersinteger7 parameter55 sp E selected_real_kind(?)

integer7 parameter55 dp E selected_real_kind(2)

&hen to specif a doue precision itera7 -etpe5 4.M?Odp


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1ind nu*er e,a*peprogram+ind_eam!le

implicit none

integer, parameter## d! = selected_real_kind)1-

integer, parameter## e! = selected_real_kind)1.

real## a

double precision## /, $ real)e! ## d

a = 1234-(0."1234-(0."1234-(0."1234-(0.0

/ = 1234-(0."1234-(0."1234-(0."1234-(0.0

$ = 1234-(0."1234-(0."1234-(0."1234-(0.0_d!

d = 1234-(0."1234-(0."1234-(0."1234-(0.0_e!

print*, 'real)4 ', a

print*, 'real)4 ', /

print*, 'real). ', $

print*, 'real)1" ', d

end program+ind_eam!le


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Intrinsic functions forco*pe, variaes real(P) / returns the rea part of P

aimag(P) / returns the i*aginar part of P

conjg(P) / return co*pe, conugate of P

abs(P) / returns *agnitude of P

P E cmplx(a7 ) / for* co*pe, nu*er

fro* t-o rea variaes a and


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Initiaising variaes&here are three -as to initiaise variaes

-ith starting vaues5

During the decaration5real## mass1 = -"3, mass2 = 1"""

In a datastate*ent (version )5

real## mass1, mass2,

datamass1, mass2 -"3, 1""" In a datastate*ent (version 3)5

real## mass1, mass2,

datamass1 -"3, mass2 1"""


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8epeating initiaising data If a ist of variaes need to e initiaised -ith

the sa*e vaue7 -e can repeat the*

Instead of5

integer## a, /, $, d

dataa, /, $, d ", ", ", "

We can use5integer## a, /, $, d

dataa, /, $, d 4 * "Works for initiaising arras too


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%rith*etic operators%ddition +

Sutraction >

$utipication C

Division

!,ponentiation CC

e.g. 43E 4 CC 3 For integer po-ers7 it is faster to *utip

*anua


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8eationa operators Greater than .gt.or

Greater than or e=ua .ge.or !

'ess than .lt.or "

'ess than or e=ua .le. or "!

!=ua .e#.or !!


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'ogica operators e=uivaence .ne#v.


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Si*pe e,a*pe progra*program age_!rogram

implicit none

integer## ear, age, !resent_ear = 2"11

character)1" ## m_name ! string of 10 chars

print*, 'hat is o%r name'

read*, m_name

print*, 'hat ear were o% /orn'

read*, ear

age = !resent_ear 5 ear

print*, 'Hello', m_name, 'o% are of age', age

end program age_!rogram


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Data tpe conversions


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!,picit data tpe conversionWe can e,picit force data tpe conversions7

ust to e certain

int(,) E converts to integer real(,) E convert to rea

dble(,)7 dfloat(,) E convert to doueprecision

cmplx(,) E converts reainteger to co*pe,(no i*aginar part)

cmplx(,7 ) E converts reainteger toco*pe, (rea , and i*aginar )


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!,a*peinteger## a = 3, $ = 0

real## / = 43, d

complex## e

$ = a 6 /

d = real)a 6 /

e = cmplx)/, $ ! not e = (b, cprint*, $, d, e


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Do oop Snta,5

do[7ar = start, end, ste!]

statements

end do

var*ust e an integer

!,a*pe5doi = 1, 1", 2

total = total 6 i

end do


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Do oop (no counter) Infinite do (no var) can e stopped

-ith exit

do

if)condition then

exit end if

end do


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I*pied Do oop an e used for5 Initiaising arras

8eading a ist of vaues (usefu for 3D arras) rinting a ist of vaues

Snta,5 )statement, var= start, stop, step

print*, )i, i = ", 2", 2 read*, )ta/le)i, i = 1, 1" real## 7al%es)2"

7al%es = ) )"2 * i, i = 1, 2"


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8eading -ith i*pied do o*pare this code5

doi = 1, 1"

read *, 7al%e)i

end doWith this code5

read*, )7al%e)i, i = 1, 1" Is there a difference6


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Whie oop Introduced in Fortran 90 (so*e Fortran

co*piers supported it)

Snta,5do while)expression

statements

end do

!,a*pe5do while)total .lt.1""

total = total 6 1

end do


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If then ese... !,a*pe5

if)dis$rim .gt." then

print*, '8here are two roots'

else if)dis$rim .eq." then

print*, '8here is a single root'

else

print*, '8he roots are $om!le'

end if


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Seect state*entselect case)o!tion

case)1

print*, '9ardening'

case)2#1"

print*, ':lothes'

case)11, 12, 1-, 2"#3"

print*, 'esta%rant'

case default

print*, ':ar!ar+'

end select


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%rras %rras are variaes that consist of *utipe

ee*ents of the sa*e tpe

Fortran supports up to di*ensions " defaut7 arra indices start at

!,a*pes5integer## ta/le1)2", 7e$tor)-, -

complex, dimension)3, 3 ## matri1, matri2

ta/le1)1 = 3

7e$tor)2, 3 =


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usto* arra indices and

initiaisationWe can redefine the inde, range

integer## n%m/er)" # 1", $ost)


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%rra initiaisation using a

data state*entWe can aso initiaise arras using a data

state*ent (fro* Fortran )

real## readings)-, $o%nt)3, 7oltage).datareadings 12, ",


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Ro- *utidi*ensiona arras

are stored nike 7 Fortran stores *utidi*ensiona

arras using column-order

indices to the eft change fastest I*agine a 3D arra5 integer55 a(37 4)

In Fortran7 this arra is stored in this order5

Ha(7)7 a(37)7 a(73)7 a(373)7 a(74)7 a(374)

a!1"1#

a!2"1#

a!1"2#

a!2"2#

a!1"$#

a!2"$#


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%rra sicing 'ike $%&'%"7 -e can seect su>sections or

sices of an arra

Snta,5 array_name)start#end#stride

integer## a)1", /)-, total

dataa 1, 2, 3, 4, -, (, 0, ., , 1"

/ = a)3#0 a)3,a)4,a)-,a)(,a)0

/ = a)#- a)1,a)2,a)3,a)4,a)-

/ = a)(# a)(,a)0,a).,a),a)1"/ = a)1#1"#2 a)1,a)3,a)-,a)0,a)

/ = a)) 2, -, 0, ., a)2,a)-,a)0,a).,a)

total = sum)a)2#0 ! um is an intrinsic function


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%rra operators


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Where...ese-here...end

-here %o-s us to perfor* an operation on on

certain ee*ents of an arra (ased on a

*asking condition)e.g. where)a > "" a = 1" a

&his perfor*s a reciproca on on theee*ents of arra athat are positive


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Where...ese-here...end

-here$ore genera for*5where)logical expression

array operations

elsewhere

array operations

end where

For e,a*pe5

where)a > "" a = log)a ! log of positive elements

elsewhere

a = "" ! set negative elements to "ero

end where


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Intrinsic vector*atri,

functions&ranspose a E transpose()

Dot product c E dot_product(a7 )

$atri, *utipication (*atrices *ust confor*) c E matmul(a7 )


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$atri, e,a*pe Given t-o *atrices % and "

We -ant to -rite a Fortran progra* thatco*putes and prints the foo-ing5

E %"%&

A=

[1 2

3 4

] B=

[5 6

7 8

]


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In=uiring and reshaping

arras s E shape(a) returns the shape of arra a

n E si%e(a) returns the tota nu*er of

ee*ents in arra a n E si%e(a7 i) returns the tota nu*er of

ee*ents aong di*ension iof arra a

c E reshape(7 s) function to change shape

of arra bto shape of a(stored as s) e.g. $ = reshape)/, )3, 4


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!,a*pe arra progra*programresha!e1

implicit none integer## a)4, /)2, 2, $)2, 2, i, , d)3, -

dataa 1, 2, 3, 4, / 1, 2, 3, 4

print*, '?ha!e of a=', shape)a

print*, '?ha!e of /=', shape)/

print*, 'si@e of dim 2=', size)d, 2

$ = reshape)a, )2, 2

print*, 'Aatri /'

doi = 1, 2

print*, )/)i, , = 1, 2

end do print*, 'Aatri $'

doi = 1, 2

print*, )$)i, , = 1, 2

end do

end programresha!e1


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#utput


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%ocatae arras ti*e

se aocatae arras if their siPe is not kno-nreal, allocatable## arra)#

In the code7 to aocate this arra to nee*ents

allocate)arra)n

When not needed7 -e can free the *e*ordeallocate)arra

Qou can aocate *utidi*ensiona arras

real, allocatable## arra)#, #, #


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For*atting screen outputWe have used printC7 var7 var37 var4

&he asterisk C *eans use ist>directed output

(co*pier auto*atica for*ats thevariaes)

For *ore fine for*atting contros7 there aret-o *ethods5

Incuding a for*at specifier string sing the formatstate*ent


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For*atting screen output For*at specifier string5

print')1, i-, -, f1".', inde, densit

For*at state*ent5

print1", inde, densit1" format)1, i-, -, f1".

&hese e,a*pes oth use the foo-ingfor*atting for each ine5 #ne space (,)7 then

Integer nu*er -ith -idth of 2 paces (i2)7 then

Five spaces (2,)7 then

8ea nu*er -ith -idth of 0 paces and A deci*apaces (f0.A)


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For*atting specifiers Nx/ < ank spaces

iW/ integer nu*er -ith W paces

fW.D rea nu*er -ith W tota paces(incudes deci*a point) and D deci*apaces

eW.DeE/ rea nu*er in e,ponentia for*at

-ith W paces7 D deci*a paces7 !e,ponentia paces (e.g. 0.,,,ePP)

enW.D engineering notation (e47 e?7 e97...)

esW.D scientific notation


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$ore for*at specifiers aW/ character -ith W paces

tN/ *ove to asoute screen position ne- ine (end of record)

N() > repeat the for*at inside () Nti*es


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!,a*peprogramad7format

implicit none

integer## iteration = 23, i

real## estimate = 231234-(0..00(, error = 04324

real, parameter## !i = 3141-2(-4

print')B8he 7al%e of !i isB, 1, f0-', !i

print- ! print column headings

doi = 1, 1"

print1", iteration, estimate, error

end do

- format)'Cteration', 4, 'Dstimate', 4, 'Drror'

1" format)i4, 4, f1"-, 4, f41

end programad7format


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#utput


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#pening te,t fies for

reading-riting&o open a te,t fie for reading-riting5

open)%nit = num, file = filename,

stat%s =mode, [options]

!ach fie opened has associated -ith it a unitnu*er (unit E is optiona)

&he status sets the *ode of the fie5old/ the fie aread e,ists and is not to e repaced

ne&/ create a ne- fie (the fie *ust not e,ist)replace/ over-rite e,isting fie (if it e,ists) or create a

ne- one (if it does not e,ist)

scratch/ -riting to te*porar fie that is auto*aticadeeted -hen cosed


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Fie opening Hoptions positionE BappendB (appends data to BodB

e,isting fie)

actionE read-riteread-rite read / cannot perfor* -rites on this fie

-rite / cannot perfor* reads on this fie

read-rite / can oth -rite and read


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Fie opening e,a*pes&o open an e,isting fie Bdata.datBopen)%nit = 1", file = 'datadat', stat%s = 'old'

&o open an e,isting fie Bdata.datB (appends-ritten data)open)1", file = 'datadat', stat%s = 'old',!osition = 'a!!end'

&o -rite data to a ne- fie Boutput.t,tB that doesnot e,ist

open)2, file = 'o%t!%ttt', stat%s = 'new'

8epace an e,isting fie Boutput.datB or create it ifit does not e,istopen)-, file 'o%t!%tdat', stat%s = 're!la$e'


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osing fies that are openWhen a fie is not used an*ore7 it is

reco**ended that it e cosed

When -riting7 cosing a fie -i ensure datain the *e*or uffer is -ritten to disk

Snta,5

close)num


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Writing to a fie Snta,5

&rite(num7 fmt7 Hoptions)7 var17 var27 ...

numis the unit nu*er of the fie (C is theter*ina e.g.&rite(C7 C) is e=uivaent to printC7)

fmtis the for*at specifier string (can use C)

Hoptions incude rec7 err7 end7 advance

If using for*at specifier string and -ant touse *ini*a spacing7 -e can use a B0 -idthBfor i7 a7 f (ut not e7 en7 es)

e.g. i07 a07 f0.0


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Writing e,a*pe integer## iter, i

real## est, error

open)-, file = 'o%tdat', stat%s = 'new'

write)-, 1" ! write column headings

1" format)'Cter', 4, 'Dstimate', 4, 'Drror'

doi = 1, 1""

write)-, 1- iter, est, error end do

1- format)i4, 4, f04, 4, f-2

close)-


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#pening a Bne-B fie that

aread e,ists Fortran -i give a runti*e error if opening a

Bne-B fie that aread e,ists

&his prevents the progra* fro* over-ritinge,istingfies (so it is a safet precaution)

For e,a*pe5

Et line 0 of file sim!leritef")%nit = -, file = ''

Fortran r%ntime error# File'sim!ledat' alread eists


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#pening an BodB fie that

does not e,istEt line 0 of file sim!leritef" )%nit= -, file = ''

Fortran r%ntime error# File 'sim!ledat'does not eist


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8eading fro* a fie Snta,5

read(num7 fmt7 Hoptions)7 var17 var27 ...

fmtE C (ist>directed input) is good for *ost

cases&he for*at specifiers ao- ver fine contro

-hen nu*ers are not separated spaces ordeci*a points

For e,a*pe7 if the data fie has a rea7 an integer

and a rea -ith no spaces5

34.M2?3M44.M?

We can use the foo-ing for*at specifier5

format)f04, i2, f(4


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8eading rea nu*ers %nother e,a*pe5

4M29 -ith f.2 -oud transfer as 4.M29

f.M -oud transfer as 4.M29 When reading rea nu*ers -ith a deci*a point

and a space after fractiona part7 the D part offW.D is overridden and W determines precision

For e,a*pe (note bis a ank space) b9.439b-ith fA.4 -oud transfer as 9.439 (the .4 isoverridden)


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8eading rea nu*ers For e,a*pe7 given the foo-ing nu*er

3.A34M243M4

If -e read using f0.7 -e transfer3.A34M2 (. is overridden to fi up to 0paces)

If -e read using f4.7 -e transfer 3. (. is

overridden ut sti get truncation ecauseon 4 paces)

&his on appies to reading7 not -riting


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8eading unti end of fie If -e do not kno- ho- *an vaues to read7

-e need to detect the end of fie read)unit, fmt, end=num 7ar1, 7ar2

When -e reach end of fie7 progra* u*ps tonum

do

read)-, *, end= 2", 7al%e

end do2" print*, Gea$hed end of file

hecking iostat (see ne,t side) is preferredover using end


79/145


!rror handing&o hande e,ceptions in read-rite7 -e

pass an integer as iostatinteger## ios

read)unit, fmt, iostat= ios, 7ar1, 7ar2

write)unit, fmt, iostat= ios, 7ar1, 7ar2

If the integer iosis5

negative / end of record or end of fiepositive / error detected0 / no proe*s


80/145


!rror handing e,a*pe

integer## ios

real## a

do

read)-, *, iostat= ios, a

if)ios .gt." then

print*, 'ead error'

stop ! abort program

else if )ios .lt."then

print*, 'Dnd of file rea$hed'

exit! exit the do loop

end if

end do


81/145


"ackspace and re-ind backspaceunit_num after each read-rite7 the fie pointer advances

to the ne,t record or ine ackspace *oves the pointer ack to the

previous record or ine after advancing

re&indunit_num

repositions pointer ack to the eginning ofthe fie


82/145


"ackspace e,a*pe 'et us sa -e have an open fie (2) that contains5

34

M

read(27 C)7 vaue E

read(27 C)7 vaue E 3 read(27 C)7 vaue E 4

ackspace 2

read(27 C)7 vaue E 4 (not 3)


83/145


Suprogra*s It is good practice to spit a arge progra* into

s*aer suprogra*s

ro*otes readaiit and re>usaiit We pass data as argu*ents to suprogra*s

(du** variaes)

" defaut7 argu*ents arepassed by referenceinFortran (uness e,picit specified)

Fortran supports t-o tpes of suprogra*s Functions

Suroutines


84/145


Functions Functions accept data as argu*ents and

direct return one vaue

e.g. , E sin(theta)7 P E c*p,(re7 i*)We need to e,picit state the data tpe of

the argu*ents and return vaue

" defaut7 the function na*e is the return

variae#r -e can use the result cause

&here are severa -as to decare the returnvaue of a function


85/145


8eturn tpe of a function$ethod 5

functionadd),

implicit none real, intent(in)## ,

real## add

add = 6

end functionadd

&o ca this function7 c E add(a7 )


86/145


87/145


8eturn tpe of a function$ethod 45

functionadd), result)@


real## @

@ = 6

end functionadd



88/145


8eturn tpe of a function$ethod M5

realfunctionadd), result)@


@ = 6

end functionadd



89/145


Intent of argu*ents&hough optiona7 it is reco**ended to state the

intent of each argu*ent to a function orsuroutine

%o-s co*pier to pick up ca errors

&here are three tpes of intent5 intent(in)

intent(out)

intent(inout)

%rgu*ents -ith intent(out) and intent(inout)refect an changes ack to caing progra*(pass reference)


90/145


!,a*pereal functionestimate), error

implicit none

real, intent)in ##

real, intent)out ## error

estimate = #some code$

error = #approx estimation error$

end functionestimate&his function returns the esti*ate direct

ut aso the esti*ate error via theargu*ents


91/145


Suroutines Suroutines do not return a vaue direct

&he can indirect return vaues via the

argu*ents (intent of outor inout)&hough optiona7 a argu*ents shoud have

their intent specified

se the callstate*ent to ca a suroutine


92/145


Suroutine e,a*pesubroutineadd), , res%lt

implicit none

real, intent)in ## ,

real, intent)out ## res%lt

res%lt = 6

endsubroutineadd

&o ca this suroutine5

calladd)a, /, $


93/145


%ternate returningWhen e,ecutation reaches the end

state*ent of a function or suroutine7 -e

return ack to the caing progra* If -e -ant to return ack via an aternate

*eans7 -e can use the returnstate*ent


94/145


%ssu*ed siPe arras and

strings


95/145


Interna suprogra*sWe can define suprogra*s to e kno-n and

used on the *ain progra* (often caed

utiities)&hese suprogra*s are internaland cannot

e caed other *ain progra*s

sed functionssuroutines that are on

usefu for the current *ain progra*


96/145


Snta, for interna

suprogra*sprogramprogram_name

implicit none

[executable statements]

contains

[function or subroutine]

end program!rogram_name


97/145


!,a*pes of interna

suroutines First e,a*pe re=uires the siPe of the arra

to e passed to suroutine

Second e,a*pe uses the shape() functionso -e on need to pass the arra

Suroutine in second e,a*pe is *oregeneric

program internal


98/145


programinternal

implicit none

integer## a)3, 3

dataa 1, 2, 3, 4, -, (, 0, ., call!rintAatri)a, 3, 3

contains ! internal subroutine

subroutine!rintAatri)a, n%mows, n%m:ols

implicit none

integer, intent)in ## n%mows, n%m:ols, &

a)n%mows, n%m:ols

integer## i,

doi = 1, n%mows

print*, )a)i, , = 1, n%m:ols

end do

end subroutine!rintAatri

end programinternal

program internal


99/145


programinternal

implicit none

integer## a)3, 3

dataa 1, 2, 3, 4, -, (, 0, ., call!rintAatri)a

contains ! internal subroutine

subroutine!rintAatri)a

implicit none integer, intent)in ## a)#, #

integer## i, , s)2

s = shape)a

doi = 1, s)1 print*, )a)i, , = 1, s)2

end do

end subroutine!rintAatri

end programinternal


100/145


sing e,terna suprogra*sWe can ca functions or suroutines that are

e,terna to the progra*

&his ao-s us to uid up a BirarB of usefuprocedures for future use

We can specif -hich procedures aree,terna (*andator for functions)

&-o *ethods -e can use5 sing externalstate*entattriute

Decaring an e,picit interface (highreco**ended)


101/145


!,a*pe using e,terna

functionprogrameam!le1

implicit none

real## = 3, = 4

real, external## $al$adi%s

print*, 'adi%s = ', $al$adi%s),

end programeam!le1

real function$al$adi%s),

implicit none


$al$adi%s = sqrt) ** 2 6 ** 2

end function$al$adi%s


102/145


!,a*pe using e,terna

suroutineprogram eam!le2

implicit none

real## = 3, = 4, r

external$al$adi%s

call$al$adi%s), , r

print*, 'adi%s = ', r

end programeam!le2

subroutine$al$adi%s), , r

implicit none real, intent)in ## ,

real, intent)out ## r

r = sqrt) ** 2 6 ** 2

end subroutine$al$adi%s


103/145


!,terna function (using

e,picit interface)programeam!le1

implicit none

real## = 3, = 4

interface

real function$al$adi%s),


end function$al$adi%s

end interface

print*, 'adi%s = ', $al$adi%s),

end programeam!le1


104/145


!,terna suroutine (using

e,picit interface)programeam!le2

implicit none

real## = 3, = 4, r

interface subroutine$al$adi%s), , r


real, intent)out ## r

end subroutine$al$adi%s

end interface


105/145


Wh use interfaces6 %o-s the co*pier to check -hether ou

have the correct argu*ents to the e,ternafunctionsuroutine ca

If ou use external7 the co*pier cannotcheck the argu*ents (*a cause runti*eerrors)

&r re*oving one of the argu*ents to

cac8adius and see ho- the co*pier reacts external*a e used if the

functionsuroutine is not direct caed (see


106/145


%nother e,a*pe of e,terna

dangerprogrammain

implicit none

real, external## add

print*, '8he res%lt is', add)3, 4end programmain

real functionadd)a, / result)$

implicit none

real, intent)in ## a, /

$ = a 6 /

end function add

OUTPUT:

8he res%lt is ."".2-D


107/145


BSaveB variaes ;ariaes decared in suprogra*s are

destroed after returning (i.e. voatie)

We can decare save variaes that re*ain(and retain their vaue) after the suprogra*has finished

integer, save## i

Initiaising a variaein a suprogra* *akesit automaticallya BsaveB variae

integer## i = "


108/145


!e*enta functions Functions -ith scaar du** argu*ents can

on e passed scaars7 e.g.

realfunctionadd)a, / real## a, /

add = a 6 /

&he aove function on adds t-o scaars7 a

and If -e define it as elemental7 the function

can e used for adding confor*ing arras

elemental real functionadd)a, /

Fu e,a*pe of an ee*enta


109/145


Fu e,a*pe of an ee*enta

functionprogramelem implicit none

real, dimension)3 ## a, /

dataa 1, 2, 3, / -, 3, 1 print*, add)a, /

contains

elemental real functionadd)a, /

real, intent)in ## a, /

add = a 6 /

end functionadd

end program elem


110/145


$oduesWriting interface ocks is tedious -hen

caing *an different e,terna suprogra*s

Fortran 90 provides a -a of groupingreated suprogra*s (as -e as tpedefinitions and variaes) into a singe iraror module

o*piing a *odue creates a C.*od fie thatcontains the interfaces

" using a *odue7 -e do not need to -ritean interface ock for each suprogra*


111/145


Snta, for *oduesmodulemodule_name

[variable declarations]

[type definitions]

contains

[functions and subroutines]

end modulemodule_name


112/145


!,a*pe of a *oduemodulegriffith_st%dent

typest%dent

integer## n%m/er

character)3" ## name

real## g!a end typest%dent

integer ## n%m?t%dents, netI%m

contains

subroutineadd_st%dent)name, g!a

end subroutineadd_st%dent

end modulegriffith_st%dent


113/145


sing a *odueWhen co*piing a *odue7 a .*od fie (e.g.

griffithOstudent.*od) -i e created

&o use a *odue7 -e use the usestate*ent e.g.

programst%dentJrogram

usegriffith_st%dent

implicit none


114/145


sing *odues When using a *odue7 a tpe definitions and

variaes defined there -i e avaiae in the*ain progra*

It is possie to BhideB variaes or suprogra*s(as private)

% suroutines and functions can e caed-ithout the need for an e,picit interface ock

(the co*pier can sti check our argu*entsJJ)&herefore7 it is reco**ended to put our o-n

suroutinesfunctions into *odues


115/145


8ecursive functions So*e *athe*atica agorith*s are recursive

nature

For e,a*pe7 the factoria52J E 2 , MJ

MJ E M , 4J

4J E 4 , 3J

etc. In Fortran7 on recursive functions can ca

the*seves


116/145


8ecursive functions nike nor*a functions7 the function na*e

cannot e used as the return variae (-h6)

We add the resultstate*ent For e,a*pe5recursive functionfa$torial) result)res

real, intent)in ##

real## res

end functionfa$torial


117/145


8ecursive functions %nother *ethod of decaring the tpe of the

resut variae5

real recursive functionfactoria(,) result(res) or

recursive real functionfactoria(,) result(res)

8e*e*er to incude a stopping condition

-hen using recursive functions se sparing as the are so-


118/145


!,a*pe of recursive functionreal recursive functionfa$torial) result)fa$t

real, intent)in ##

if) .gt.1 then fa$t = * fa$torial) < 1

else

fa$t = 1 ! stopping condition

end if

end functionfa$torial


119/145


Derived data tpes %rras can on store ee*ents of the sa*e

data tpe

Derived data tpes can group different datavariaes (kno-n as structures in )

!,a*pe5

typest%dent

integer## n%m/er character)2" ## name

real## g!a

end typest%dent


120/145


Derived data tpes&o decare a variae of the derived data

tpe5

type)st%dent ## /o/We use the operator to access the

*e*ers

/o/Kname = 'o/'

/o/Kn%m/er = 1234-/o/Kg!a = -.


121/145


!,a*pe of reading into

derived data tpestype)st%dent ## adam, e7e

adam = st%dent)1234-, 'Edam_?andler', -(

open)1", file= 't!eett', status= 're!la$e'

write)1", * adam ! write using listed %&'

close)1"

open)12, file= 't!eett', status= 'old'

read)12, * e7e ! read using listed %&'close)12

print*, adam

print*, e7e


122/145


Function overoading B#veroadingB *eans caing different

suprogra*s using the sa*e generic na*e

Which suprogra* is caed depends on the tpeof the argu*ents

For e,a*pe7 -e *ight have t-o versions of thefunction na*e func(,) sfunc(,) if , is a rea

dfunc(,) if , is a doue precision

#veroading ao-s Fortran to auto*aticachoose to ca sfunc() or dfunc() depending onthe tpe of ,


123/145

$ d d


124/145


$odue procedure

overoading Functions defined in an *odue aread have

an e,picit interface

So -e donBt need to define another e,picitinterface

&o overoad *odue functions sfunc anddfunc5

interfacef%n$ module proceduresf%n$, df%n$

end interfacef%n$


125/145


#perator overoading Suppose -e -rite a function that processes

t-o derived tpes (e.g. add)

8ather than caing the add() function7Fortran 90+ ao-s us to BoveroadB aconfor*ing arith*etic operator

For e,a*pe7 -e can BoveroadB the +

operator to ca the add function$akes progra* *ore readae

! f t


126/145


!,a*pe of operator

overoading 'et us define a poar coordinate derived tpe

in a *odue5

type!olar real## mag

real## angle

end type!olar

In our *odue7 -e define an poar%ddfunction that perfor*s an addition inrectanguar co>ordinates

! f t


127/145


!,a*pe of operator

overoadingfunction!olarEdd)a, / result)$

type)!olar, intent)in ## a, /

type)!olar ## $

We can overoad the + operator via theinterface

interfaceoperator)6

module procedure!olarEdd

end interface


128/145


!,a*pe of operator

overoading See the fu poaro*p source code

f t ti i ti


129/145


gfortran opti*isationWe can add the foo-ing s-itches for *ore

etter opti*isation >#3 or >#4 (eve 3 opti*isation is defaut) >funro>oops

>*tune E arch(opti*ises for a particuarprocessor) native ( used to co*pie) 7 pentiu*47

pentiu*M7 pentiu*>*7 core37 etc.

>*fp*athEsse >***,7 >*sse7 >*sse37 >*sse4 ....

http5gcc.gnu.orgoninedocsgcc>4.M.?gcc#pti*iPe>#ptions.ht*

http5gcc.gnu.orgoninedocsgcc>M.4.4gcci4A?>and>,A?O003d?M>#ptions.ht*

< t B th d
http://maxwell.me.gu.edu.au/sso/fortranhttp://gcc.gnu.org/onlinedocs/gcc-3.4.6/gcc/Optimize-Options.htmlhttp://gcc.gnu.org/onlinedocs/gcc-4.3.3/gcc/i386-and-x86_002d64-Options.htmlhttp://gcc.gnu.org/onlinedocs/gcc-4.3.3/gcc/i386-and-x86_002d64-Options.htmlhttp://gcc.gnu.org/onlinedocs/gcc-3.4.6/gcc/Optimize-Options.htmlhttp://maxwell.me.gu.edu.au/sso/fortran


130/145



131/145


Statistics *odue e,a*pe

(statistics.f90)&his progra* shoud read a data fie (reg.dat)

&his fie contains so*e header info and then 3

cou*ns of data (, and ) Functions and suroutines are -ritten to find

*ean7 variance7 and ine of est fit

&hese suprogra*s are grouped into a singe

*odue (statistics)


132/145


Static iraries 8ather than co*piing suprogra*s each

ti*e7 -e can store as oect fies (C.o) and

ink into the *ain progra* ater (saves ti*e) 'inking ots of oect fies can e a hasse

(esp. if ou donBt kno- -hich ones ou arecaing)

% static irar (C.a or C.i) is an archive forstoring *an reated oect fies into one fie

We si*p ink the static irar -ith our*ain progra*


133/145


"'%S and '%%1 iraries "asic 'inear %gera Suprogra*s ("'%S) and

'inear %gera ackage ('%%1)

"'%S contains routines for vector and *atri,*utipication (proa redundant due to

Fortran 90 capaiities) '%%1 contains routines for inear agera

(!;D7 S;D7 '7 T87 hoesk7 Schur7 etc.)

Generic "'%S and '%%1 source code can e

do-noaded fro* http5---.neti.orgapack o**ercia Fortran packages often co*e -ith

opti*ised '%%1 iraries (Inte $1'7 %$D%$'7 etc.)
http://maxwell.me.gu.edu.au/sso/fortranhttp://www.netlib.org/lapack/http://www.netlib.org/lapack/http://maxwell.me.gu.edu.au/sso/fortran


134/145


'%%1 iraries for -indo-s Static '%%1 iraries are provided -ith

co**ercia co*piers

We can uid a '%%1 static irar usingour o-n co*pier

Ro-ever7 the irar usua on inks tocode co*pied using sa*e co*pier

ie. a '%%1 irar *ade using gfortrancannot e inked into a progra* co*piedusing Inte ;isua Fortran


135/145


'%%1 na*ing convention#f the for* UQQVVV

U7 indicates the data tpe as foo-s5

S 8!%' D D#"'! 8!ISI#< #$'!U V #$'!UC? or D#"'! #$'!U

QQ7 indicate the tpe of *atri, (or of the*ost significant *atri,)

VVV7 indicate the co*putation perfor*ed


136/145



137/145


aing '%%1 fro* Fortran

90


138/145


sing '%%1 to cacuate

inverse of a *atri, '%%1 re=uires t-o suroutine cas (in

order)

sgetrf() > cacuates the ' deco*position of % sgetri() > uses ' deco*p of % to find its

inverse

8ead the docu*entation for each suroutine sgetrf.pdf or sgetrf.t,t

sgetri.pdf or sgetri.t,t

Write an interface ock for oth suroutines

i '%%1 t t


139/145


sing '%%1 to cacuate

eigenvectors and eigenvauesWe -i consider the '%%1 routinessyevd

for finding eigenvectors and eigenvauesfro* a s**etric *atri,

Docu*entation specifies the necessar siPeof each *atri, (-ork7 i-ork)

If -orking -ith doue precision *atrices7use dsyevd


140/145


sefu inks for using '%%1 http5---.neti.orgapackug(users

guide containing descriptions of a '%%1routines)

aing Fortran 90
http://maxwell.me.gu.edu.au/sso/fortranhttp://www.netlib.org/lapack/lug/http://www.netlib.org/lapack/lug/http://maxwell.me.gu.edu.au/sso/fortran


141/145


aing Fortran 90

suprogra*s fro* $%&'%" o*ines the speed of Fortran -ith $%&'%"

&here are t-o -as of doing this5

$!U fies 'oading of dna*ic iraries (D''s)

$!U fies are heavi docu*ented in $%&'%"

We -i ook at the second *ethod

Dna*ic iraries are si*iar to staticiraries7 e,cept that the are dna*icainked at runti*e


142/145


reating a dna*ic irar In Windo-s7 the e,tension is C.d (in 'inu,7 it

is C.so)


143/145


reating a header fie$%&'%" re=uires an acco*paning header

fie

onsists of the function na*e foo-ed anunderscore. e.g. add > addO

!,a*pe5

realfunctionadd)a, /

real, intent)in ## a, / add = a 6 /

end functionadd


144/145


header fie&he header fie (add.h) -oud consist of externfloatadd_)float*a, float*/;

&he corresponding data tpes in integer E int rea E foat

doue precision E doue

character E char If using arra argu*ents7 the siPe of the

arras *ust e passed

'oading and caing the D''


145/145

'oading and caing the D''

in $%&'%"We use the oadirar function in $%&'%"

loadli/rar)'li/add', 'addh'

#nce this has een oaded7 -e ca thefunction

a = $allli/)'li/add', 'add_', 2, 3

fortran workshop

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