I/O performance blues

[Arjen Markus]

I have not studied the code in detail, but what struck is the use of
BACKSPACE. Could that cause a performance penalty?

Regards,

Arjen

2013/11/25 Salvatore Filippone <filippone.salvatore@gmail.com>:
> HI Jerry,
> Thanks.
> Salvatore
>
> Source code sent offlist
>
> On Mon, Nov 25, 2013 at 6:58 PM, jvdelisle <jvdelisle@charter.net> wrote:
>> When I have some time in the next few weeks, I will take a look at your
>> example.
>>
>> Regards,
>>
>> Jerry
>>
>>
>>
>> -------- Original message --------
>> From Salvatore Filippone <filippone.salvatore@gmail.com>
>> Date: 11/25/2013 6:31 AM (GMT-08:00)
>> To gfortran <fortran@gcc.gnu.org>
>> Subject I/O performance blues
>>
>>
>> Hello
>> In the last few days I have investigated a rather disappointing
>> phenomenon related to I/O.
>> The Harwell-Boeing storage format is a rather well-known format for
>> storing matrix data on file; sample codes and pointers to further
>> documentation are available at http://math.nist.gov/MatrixMarket/
>>
>> The input is via read statements as follows
>> ==================================================
>>     open(infile,file=filename, status='OLD', err=901, action='READ')
>>
>>     read (infile,fmt=fmt10) mtitle_,key,totcrd,ptrcrd,indcrd,valcrd,rhscrd,&
>>          & type,nrow,ncol,nnzero,neltvl,ptrfmt,indfmt,valfmt,rhsfmt
>>     if (rhscrd > 0) read(infile,fmt=fmt11)rhstype,nrhs,nrhsix
>>     allocate(icp(ncol+1),ia(nnzero),val(nnzero),stat=ircode)
>>     if (ircode /= 0 ) then
>>       write(*,*) 'Memory allocation failed'
>>       goto 993
>>     end if
>>
>>     read (infile,fmt=ptrfmt) (icp(i),i=1,ncol+1)
>>     read (infile,fmt=indfmt) (ia(i),i=1,nnzero)
>>     if (valcrd > 0) read (infile,fmt=valfmt) (val(i),i=1,nnzero)
>>
>>     close(infile)
>> ===================================================
>> Now, at the Matrix Market site there is an alternative implementation
>> of this I/O in C.
>> It turns out the C version consistently outperforms the Fortran version!!
>>
>> [sfilippo@epsilon testhb]$ ./test_hbrd
>> File name?
>> ultrasound80.hb
>> Reading from matrix file: ultrasound80.hb
>>   nrows:      531441  ncols:      531441  nnzeros:    33076161
>> C       Time read for ultrasound80.hb:   18.724172830581665
>> Fortran Time read for ultrasound80.hb:   33.051491975784302
>> [sfilippo@epsilon testhb]$ ./test_hbrd
>> File name?
>> thm_6814k.hb
>> Reading from matrix file: thm_6814k.hb
>>   nrows:     6813804  ncols:     6813804  nnzeros:    33930324
>> C       Time read for thm_6814k.hb:   19.886425018310547
>> Fortran Time read for thm_6814k.hb:   38.642944097518921
>> [sfilippo@epsilon testhb]$ ./test_hbrd
>> File name?
>> pde-50.hb
>> Reading from matrix file: pde-50.hb
>>   nrows:      125000  ncols:      125000  nnzeros:      860000
>> C       Time read for pde-50.hb:  0.32523894309997559
>> Fortran Time read for pde-50.hb:  0.78256392478942871
>> ====================================================
>> This is with current trunk; I have seen fluctuations in the exact
>> timings when trying 4.6.4/4.7.3/4.8.2 but the overall picture is
>> pretty much the same.
>>
>> I have the full test program and many input cases available; is
>> anybody familiar with the IO in gfortran and willing to take a look?
>> And/or give me any suggestions where to look for clues and how? Should
>> I open a PR?
>>
>>
>> Thanks a lot
>> Salvatore