enhancements to open source translator fable for code porting … · 2017-08-17 · a sample...

International Journals of Advanced Research in Computer Science and Software Engineering ISSN: 2277-128X (Volume-7, Issue-6)

Research Article

June 2017

© www.ijarcsse.com, All Rights Reserved Page | 631

Enhancements to Open Source Translator FABLE for Code

Porting of Legacy Applications S. Suguna Mallika

*, Ch. Sharada

Department of CSE, CVR College of Engineering,

Telangana, India

DOI: 10.23956/ijarcsse/V7I6/0145

Abstract - With the current and young researchers moving towards object oriented languages like C++ and Java,

maintenance of legacy software developed in languages like Fortran 77 and its native versions are becoming

increasingly difficult. To ease the maintenance of legacy software it is recommended to port them to C++ or Java. But

the task of hand coding every line of the existing software is painstakingly demanding lot of resources, time, and cost.

It is practical that any automatic translator is used for this purpose and among the many tools available, FABLE is

one. FABLE which is an open source translator, however needs some enhancements in appropriate binaries to

complete the translation successfully. This work focuses on some of the common practices of FORTRAN

programming which essentially hamper the effective translation of code. A detailed account on such challenges faced

with FABLE and enhancements done to FABLE is presented in the current work.

Keywords – FORTRAN file translation, C++ conversion, porting legacy software, code porting

I. INTRODUCTION

With the advent of many new programmer friendly languages, and the younger set of scientific community

learning the new languages like C++, the maintenance of legacy software developed in languages like FORTRAN is a

complex job[1]. Hence there is a need to translate legacy software to newer languages like C++ and Java which would

simplify the job of maintenance by the novices who are well versed with only the new languages. There is an open source

translator called “FABLE” which translates the original source program written in FORTRAN to C++ [1].

II. EXISTING CHALLENGES

Though FABLE is an automatic translator from FORTRAN to C++, there are set of challenges that we face at

three levels with respect to the translation [2]. The Source program statements may need modifications to get accurate

translations to CPP.

A. Pause Command – The pause statement in FORTRAN is used for debugging purposes which halts the program and

gives control to the user. Fable cannot interpret this statement and instead halts the translation process, throwing an error

in the command window resulting in a failure of translation. The figure 1 shows the error encountered when fable

encounters the keyword “pause”.

Figure 1. Screenshot displaying PAUSE Statement Error when translating FORTRAN code

dx.doi.org/10.23956/ijarcsse/V7I6/0145

Mallika et al., International Journals of Advanced Research in Computer Science and Software Engineering

ISSN: 2277-128X (Volume-7, Issue-6)


B. Inability to process some of the mathematical functions like tanh – There are many mathematical functions which

have not been defined in the fable fem libraries. However it has been observed that the source file responsible for

mathematical functions is the intrinsics.py file for which upon some enhancements FABLE, began accepting all the

mathematical functions which it was earlier failing to do so and was creating a user defined function with the same name

and dummy code placed to avert conversion errors. The definitions for all these functions are available at intrinsics.hpp.

However FABLE would refer only to intrinsics.py file to check whether the declaration of a particular function is

available at conversion time and would refer to intrinsics.hpp only at the time of invocation of the respective function at

compile time. The screenshot of the error displayed when a function declaration is not found is as shown in figure 2 and

figure 3.

Figure 2. Error Screenshot displayed when intrinsics.py file has missing math library inbuilt functions declarations

Figure 2. Error Screenshot when intrinsics.hpp has missing definitions of inbuilt functions

C. Equivalence Statements of FORTRAN – The Equivalence statement of FORTRAN was introduced originally for

conserving the memory on the early computers which typically operated on very low RAM‟s. Non - Overlapping arrays

within a program are assigned the same memory location to save space. Most of the programming practices of legacy

programming indulged in the extensive usage of EQUIVALENCE statements due to Constraints on memory. FABLE

does translate these EQUIVALENCE statements into corresponding C++ statements replacing independent arrays

preserving the logic. However, existing FABLE constrained the acceptance of only six EQUIVALENCE statements

where in legacy code normally land up with several hundreds of such statements by virtue of memory optimization.

Hence existing FABLE renders an error during the conversion process with the error message “„with‟: is not a member of

„fem::arr_index_data<Ndims>‟” which can see highlighted in figure 4.




Figure 3. Error Screenshot of existing FABLE throwing error at 10 EQUIVALENCE statements in source code

D. Formats of FORTRAN like the “T Format” were not being implemented with Fable. Fable needs modifications in

several binaries to enhance its functionality as it has many unimplemented features of FORTRAN like t format, b format,

s format, which simply rest on throwing an errorusing tbxx utils. The translation of these formats has not been considered

in the original implementation of FABLE. Figure 5 displays the error screenshot which is due to non-handling of T

format in the source program [4].

Figure 5. Error Screenshot displaying unhandled T format version

III. ENHANCEMENTS

Several enhancements are made to the existing code to overcome the challenges listed in Section 2. Some of the major

contributions include

A. The pause statement is parsed by the cout.py and the read.py files of the fem library. These two files were modified to

overcome the translation of pause statement. A small piece of code was inserted in the cout.py to handle the pause

keyword. Figure 6 shows the code modification made to read.py to parse the pause statement during translation

successfully without any hindrance.




Figure 6. Code modification in read.py binary for handling pause statement in source FORTRAN program

And the keyword pause is added to the process body_line_function() of the read.py file which would recognize the

keyword pause upon encountering it in the FORTRAN source code. A modification in the read.py and write.py to

support the translation of pause which was earlier not supported is incorporated to enable the user driven input “go” upon

which the translator would further continue with the process of execution. After the modification of binaries to handle

pause the output is displayed as in figure 7.

Figure 7. Screenshot showing successful translation of FORTRAN program with the pause statement handled effectively

B. Inability to process some of the mathematical functions like tanh - Appropriate modifications done to the intrinsics.py

and intrinsics.hpp file where the declarations and definitions of the missing functions are placed respectively, the success

screenshot is as shown in figure 8.




Figure 8. Screenshot of successful compilation of translated CPP file with the builtin functions definitions and

declarations implemented

C. The existing implementation of FABLE which is responsible for the translation of the EQUIVALENCE statement is

supporting only 6 equivalence variables only. The code that is newly added is as shown in figure 9 after which the

converted code gets successfully compiled supporting more number of equivalence variables.

Figure 9.Original FABLE Code showing accommodating limited EQUIVALENCEs

D. T Format - For horizontal positioning along the print line, FORTRAN supports Tn format where n is a strictly

positive integer [5]. The format specifier T be preceded by a positive nonzero number.Tn tab reads from the nth column

or writes to the nth column. This feature is not supported by FABLE. As the part of FABLE enhancement, this feature is

added. To add this feature modifications are done in the write.hpp and new header file named xy.h has been created. xy.h

is the header file contains definitions of gotoxy(), wherex() and wherey() functions and gotoxy() function in C++

language is used to take the cursor to a particular co-ordinate of the screen, wherex() return current horizontal cursor

position and wherey() return current vertical cursor position. Modifications of write.hpp are shown in the figure 10.




Figure 10. Code Modification for handling one variation of T format in write.hpp binary

IV. CASE STUDY

A sample Fortran program of around 200 lines, menu driven to display ratios of various standard intrinsic

functions has been written for demonstrating the enhancements made.

C MENU DIVEN PROGRAM TO DISPLAY RATIOS

C OF STANDARD INTRINSIC FUNCTIONS

REAL*8 DSINHVAL,A,DCOSHVAL,DAS,DAC,ATAN2,DAT,DAT2

REAL*8 DSINTBL(100),DCOSTBL(100),DTANTBL(100)

EQUIVALENCE(DSINTBL,DCOSTBL,DTANTBL)

EQUIVALENCE(DARCCOSVAL,DSINHVAL,DCOSHVAL,DAS,DAC,ATAN2,DAT,DAT2)

REAL*8 J

C MENU

15 CONTINUE

WRITE(6,*) "TRIGNOMETRY RATIOS"

WRITE(6,*) " 1.Dsin"

WRITE(6,*)

WRITE(6,*) " 2.Dasin"

WRITE(6,*)

WRITE(6,*) " 3.Dsinh"

WRITE(6,*)

WRITE(6,*)

WRITE(6,*) " 4.Dcos"

WRITE(6,*)

WRITE(6,*) " 5.Dacos"

WRITE(6,*)

WRITE(6,*) " 6.DcosH"

WRITE(6,*)

WRITE(6,*)

WRITE(6,*) " 7.Dtan"

WRITE(6,*)

WRITE(6,*) " 8.Datan"

WRITE(6,*)

WRITE(6,*) " 9.Datan2"

WRITE(6,*)

WRITE(6,*) " 10.DtanH"

WRITE(6,*)

WRITE(6,*) "ENTER AN TRIGNOMETRY OPTION TO KNOW THE RATIOS"

READ(5,*) I

c OPTION 1 DISPLAY SIN RATIOS.IT RETURNS THE SINE OF GIVEN ANGLE IN RADIANS.




IF(I.EQ.1) THEN

WRITE(6,*)

WRITE(6,*)

WRITE(6,115) "DSIN TABLE RATIOS FROM 0 TO 30 DEGREES"

115 FORMAT(T15,a40)

WRITE(6,*)

WRITE(6,115) "-------------------------------------"

WRITE(6,*)

WRITE(6,110) "ANGLE" , "SINVALUE"

110 FORMAT(t20,a5,T40,a9)

WRITE(6,115) "-------------------------------------"

WRITE(6,*)

DO 160 k=0, 30

j=k

DSINTBL(K+1)=DSIN(J*(3.14159265/180))

WRITE(6,100) '|', J,'|','|',DSINTBL(J+1),'|'

100 FORMAT(T20,a,f5.0,t28,a,T35,a,t40,f5.4,t50,a)

160 continue

WRITE(6,*)

WRITE(6,115) "-------------------------------------"

c OPTION 2 DISPLAY ARCSIN VALUES.RETURNS THE PRINCIPAL VALUE OF

CTHE ARC SINE OF X, EXPRESSED IN RADIANS.IN TRIGONOMETRICS, ARC

C SINE IS THE INVERSE OPERATION OF SINE

ELSE IF(I.EQ.2) THEN

WRITE(6,*)

WRITE(6,*)

WRITE(6,215) "ARCSIN TABLE RATIOS"

215 FORMAT(T15,a40)

WRITE(6,*)

WRITE(6,215) "-------------------------------------"

DO 255 k=0, 30

j=k

DSINTBL(K+1)=DSIN(J*(3.14159265/180))

255 continue

WRITE(6,*)

WRITE(6,210) "SIN VALUE" , "ANGLE"


WRITE(6,215) "-------------------------------------"

WRITE(6,*)

DO 260 k=0, 30

j=k

DAS=DASIN(DSINTBL(K+1))*(180/3.14159265)

WRITE(6,200) '|', DSINTBL(K+1),'|','|',DAS,'|'


260 continue

WRITE(6,*)

WRITE(6,215) "-------------------------------------"

C OPTION 3 DISPLAY HYPERBOLIC SIN VALUES.PARAMETER REPRESENTS

C A HYPERBOLIC ANGLE.


WRITE(6,*)

WRITE(6,*)

WRITE(6,*) " HYPERBOLIC SIN WITH DOUBLE PRECISION"

WRITE(6,*) " RETURNS THE HYPERBOLIC SINE OF ANGLE."

WRITE(6,*)

315 FORMAT(T15,a40)

WRITE(6,*)

WRITE(6,315) "-------------------------------------"

WRITE(6,*)

WRITE(6,310) "VALUE" , "HYPERBOLIC SIN IN DEGREES"


WRITE(6,315) "-------------------------------------"




WRITE(6,*)

DO 350 K=0, 30

J=K*1.0/10

DSINHVAL=DSINH(J)

WRITE(6,320) '|', J,'|','|',DSINHVAL,'|'


350 continue

WRITE(6,*)

WRITE(6,315) "-------------------------------------"

C OPTION 4RETURNS THE COSINE OF AN ANGLE OF GIVEN RADIANS.


WRITE(6,*)

WRITE(6,*)

WRITE(6,415) "DCOS TABLE RATIOS FROM 0 TO 30 DEGREES"

415 FORMAT(T15,a40)

WRITE(6,*)

WRITE(6,415) "-------------------------------------"

WRITE(6,*)

WRITE(6,410) "ANGLE" , "DCOS VALUE"


WRITE(6,415) "-------------------------------------"

WRITE(6,*)

DO 460 K=0, 30

J=K

DCOSTBL(K+1)=DCOS(J*(3.14159265/180))

WRITE(6,400) '|', J,'|','|',DCOSTBL(K+1),'|'


460 continue

WRITE(6,*)

WRITE(6,415) "-------------------------------------"

C OPTION 5 RETUNS ARC COS VALUE


WRITE(6,*)

WRITE(6,*)

WRITE(6,515) "DARCCOS TABLE RATIOS"

515 FORMAT(T15,a40)

WRITE(6,*)

WRITE(6,515) "-------------------------------------"

DO 555 K=0, 30

J=K

DCOSTBL(K+1)=DCOS(J*(3.14159265/180))

555 continue

WRITE(6,*)

WRITE(6,510) "ANGLE" , "COSVALUE"


WRITE(6,515) "-------------------------------------"

WRITE(6,*)

DO 560 K=0, 30

J=K

DARCCOSVAL=DACOS(DCOSTBL(K+1))*(180/3.14159265)

WRITE(6,500) '|', DCOSTBL(K+1),'|',DARCCOSVAL,'|'

500 FORMAT(T20,a,f7.4,t28,T35,a,t40,f7.2,t50,a)

560 continue

WRITE(6,*)

WRITE(6,515) "-------------------------------------"


WRITE(6,*)

WRITE(6,*)

WRITE(6,*) " COMPUTE HYPERBOLIC COS"

WRITE(6,*) " RETURNS THE HYPERBOLIC COS OF ANGLE."

WRITE(6,*)

C OPTION 6 RETURN HYPERBOLIC COS IN DEGREES

615 FORMAT(T15,a40)




WRITE(6,*)

WRITE(6,615) "-------------------------------------"

WRITE(6,*)

WRITE(6,610) "VALUE" , "HYPERBOLIC COS IN DEGREES"


WRITE(6,615) "-------------------------------------"

WRITE(6,*)

DO 660 K=0, 30

J=K*1.0/10

DCOSHVAL=DCOSH(J)

WRITE(6,600) '|', J,'|','|',DCOSHVAL,'|'


660 continue

WRITE(6,*)

WRITE(6,615) "-------------------------------------"

C OPTION 7 RETURN TAN VALUE FOR GIVEN RADIANS


WRITE(6,*)

WRITE(6,*)

WRITE(6,715) "DTAN TABLE RATIOS FROM 0 TO 30 DEGREES"

715 FORMAT(T15,a40)

WRITE(6,*)

WRITE(6,715) "-------------------------------------"

WRITE(6,*)

WRITE(6,710) "ANGLE" , "TAN VALUE"


WRITE(6,715) "-------------------------------------"

WRITE(6,*)

DO 760 K=0, 30

J=K

DTANTBL(K+1)=DTAN(J*(3.14159265/180))

WRITE(6,700) '|', J,'|','|',DTANTBL(K+1),'|'


760 continue

WRITE(6,*)

WRITE(6,715) "-------------------------------------"

C OPTION 8 RETURN ARC TAN VALUE


WRITE(6,*)

WRITE(6,*)

WRITE(6,815) "ARCTAN TABLE RATIOS"

815 FORMAT(T15,a40)

WRITE(6,*)

WRITE(6,815) "-------------------------------------"

DO 855 K=0, 30

J=K

DTANTBL(K+1)=DTAN(J*(3.14159265/180))

855 continue

WRITE(6,*)

WRITE(6,810) "TAN VALUE" , "ARCTAN"


WRITE(6,815) "-------------------------------------"

WRITE(6,*)

DO 860 K=0, 30

J=K

DAT=DATAN(DTANTBL(K+1))*(180/3.14159265)

WRITE(6,800) '|', DTANTBL(K+1),'|','|',DAT,'|'


860 continue

WRITE(6,*)

WRITE(6,815) "-------------------------------------"

c OPTION 9 COMPUTE DATAN2. ARC TANGENT WITH TWO PARAMETERS




c RETURNS THE PRINCIPAL VALUE OF THE ARC TANGENT OF

c Y/X, EXPRESSED IN RADIANS.Y VALUE REPRESENTING THE

c PROPORTION OF THE Y-COORDINATE.X VALUE REPRESENTING

c THE PROPORTION OFTHE X-COORDINATE.


WRITE(6,*)

WRITE(6,*)

WRITE(6,*) "SDATAN2 COMPUTE ARC TANGENT WITH TWO PARAMETERS "

WRITE(6,*) "RETURNS THE PRINCIPAL VALUE OF THE ARC TANGENT OF"

WRITE(6,*) "Y/X, EXPRESSED IN RADIANS.Y VALUE REPRESENTING THE"

WRITE(6,*) "PROPORTION OF THE Y-COORDINATE.X VALUE REPRESENTING"

WRITE(6,*) "THE PROPORTION OFTHE X-COORDINATE."

WRITE(6,*)

WRITE(6,*)

WRITE(6,915) "ARCTAN2 TABLE RATIOS"

915 FORMAT(T15,a40)

WRITE(6,*)

WRITE(6,915) "-------------------------------------"

DO 955 K=0, 30

J=K

DTANTBL(K+1)=DTAN(J*(3.14159265/180))

955 continue

WRITE(6,*)

WRITE(6,910) "Y X" , "RESULT"

910 FORMAT(t20,a15,T40,a9)

WRITE(6,915) "-------------------------------------"

WRITE(6,*)

DO 960 K=1, 30

J=K

DAT2=DATAN2(DTANTBL(K+1), J)*180/3.14159265

WRITE(6,900) DTANTBL(J+1),J,DAT2

900 FORMAT(T20,f7.4,t28,T30,f5.0,t40,f7.2,t50)

960 continue

WRITE(6,*)

WRITE(6,915) "-------------------------------------"


WRITE(6,*)

WRITE(6,*)

WRITE(6,*) " HYPERBOLIC TAN WITH DOUBLE PRECISION"

WRITE(6,*) " RETURNS THE HYPERBOLIC TAN OF ANGLE."

WRITE(6,*)

1015 FORMAT(T15,a40)

WRITE(6,*)

WRITE(6,1015) "-------------------------------------"

WRITE(6,*)

WRITE(6,1010) "VALUE" , "HYPERBOLIC TAN IN DEGREES"

1010 FORMAT(t20,a5,T40,a9)

WRITE(6,1015) "-------------------------------------"

WRITE(6,*)

DO 1050 K=0, 30

J=K*1.0/10

DTANHVAL=DTANH(J)

WRITE(6,320) '|', J,'|','|',DTANHVAL,'|'


1050 continue

WRITE(6,*)

WRITE(6,1015) "-------------------------------------"

END IF

PAUSE

IF (I .LE. 10) GOTO 15

stop

END




V. RESULTS

Post the modifications made to the binaries of FABLE, the FORTRAN code got translated into CPP file successfully and

the results of compilation of CPP file thereof are presented in Figure 11.

Figure 11. Screenshot displaying output of successfully translated FORTRAN source code into CPP file

VI. CONCLUSIONS AND FUTURE SCOPE

The code generated through FABLE is the FORTRAN code internally embedded in a class. This class in turn invokes the

FEM (FORTRAN Emulation Library) which calls the standard C/C++ libraries. The final output is more a look alike of a

FORTRAN program than a typical C++ code. The tool could further be enhanced to replace the FORTRAN statements

with the equivalent C++ statements for the end users to emulate a hand coded translation.

ACKNOWLEDGEMENT

The authors express their whole hearted The authors would like to thank Prof. Badrinarayana, who was instrumental in

getting them introduced to this tool and encouraging them towards working on this framework. The authors express their

heartfelt gratitude to the management of CVR College of Engineering for the support and encouragement all through the

work. The authors appreciate and acknowledge the effort of the original authors of FABLE, Grosse-Kunstleve RW,

Terwilliger TC, Sauter NK, Adams PD for inspiring them towards enhancement of this work and providing open source

access for enthusiasts to further enhance the tool.

REFERENCES

[1] Ralf W Grosse-Kunstleve,Thomas C Terwilliger, Nicholas K Sauter and Paul D Adams, “Automatic Fortran to

C++ conversion with FABLE”, Open Access, Source Code for Biology and Medicine 2012.

[2] Grosse-Kunstleve RW, Terwilliger TC, Sauter NK, Adams PD: Automatic Fortran to C++ conversion with

FABLE.

[3] https://www.python.org/downloads/

[4] http://www.cse.yorku.ca/~roumani/fortran/ftn.htm.

[5] R S Dhaliwal, SK Agarwal, SK Gupta, “Programming with FORTRAN 77 A structured Approach”, New Age

International Publishers.

http://www.cse.yorku.ca/~roumani/fortran/ftn.htm

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