Error? Bug? Feature?

Too often, compilation leads to an error: 'Access violation: The instruction at address 100181b6 attempted to read from location 00000000.'

This happens when I dimension an array for (150) or greater. (125) works. So far, this happens with COMPLEX, INTEGER or REAL. Here is an example, furnished by Silverfrost under FTN95 Examples\Clearwin, and edited to spare bandwidth. This example dimensions Yarr1 as (1000).

!* Silverfrost ClearWin+ Example Code * !* plotfunc.f95 - version 1.0 29/6/99 * !* only compile using FTN95 version 1.6 or higher * !* Example of ClearWin+ graphics using the %pl format code * winapp
! ! * Module of shared data for plot *

include 'salf_about.f95'

module data_to_plot use mswin
parameter(narr=1000) integer, parameter :: rkind=selected_real_kind(15,307) integer :: param_window real (kind=rkind):: p1,p2,p3 real (kind=rkind):: yarr1(narr)

contains

! ! * Routine to prepare plot data *

subroutine prepare_data integer :: i,xx xx=0 do i=1,narr yarr1(i)=p1*sin(xx/p3)*exp(-xx/p2) xx=xx+1 enddo end subroutine prepare_data ! ! * Function to respond to PLOT button * !
integer function re_plot() call prepare_data
call simpleplot_redraw@ re_plot=2 end function re_plot ! ! * Function to display parameter box * ! integer function set_params() implicit none integer :: i ! Make sure we do not display the parameters window more than once
if(param_window < 0)return; i=winio@('%ca[Plot parameters]&') i=winio@('%ww[topmost]&') i=winio@('%sy[3d]%sf&') i=winio@('%eq[Y=P{sub 1}Sin(X/P{sub 3}) e{sup -X/P{sub 2}}]%ff%nl&',300,50) i=winio@('%ob[scored]&') i=winio@('P%sd1%sd%fl%10rf%2nl&',0.01d0,1.0d10,p1) i=winio@('P%sd2%sd%fl%10rf%2nl&',0.01d0,1.0d10,p2) i=winio@('P%sd3%`sd%fl%10rf&',0.01d0,1.0d10,p3) i=winio@('%cb&') i=winio@('%rj%^5bt[Plot]%2nl%rj%5bt[Close]&',re_plot) i=winio@('%lw',param_window) set_params=2 end function set_params end module data_to_plot

! ! ! * Main program - display window containing plot * !
program simpleplot_example use salf_about use data_to_plot use mswin implicit none integer :: i p1=1.5;p2=150.0;p3=15 param_window=0 call prepare_data i=winio@('%ca[SimplePlot example program]&') i=winio@('%mi[icon_1]&')
i=winio@('%ww[no_border]&') i=winio@('%mn[&File[E&xit],&Options[Set &Parameters]]&','EXIT',set_params) i=winio@('%mn[&Help[About]]&',about_box_cb) i=winio@('%pl[x_axis='Time(Miliseconds)',y_axis=Amplitude,'&
//'title='Sample plot',colour=red]&',& 400,300,narr,0.0d0,1.0d0,yarr1) i=winio@('%pv') end

resources

icon_1 icon salflogo.ico

Is there a workaround, other than using smaller arrays? I'd hate to think this freebie is limited to such small arrays.
😦 😦

kaliuzhkin

There may be an internal ClearWin+ limit when using the original interface to SIMPLEPLOT (i.e. %pl without [native]). As John says, the remedy may be to try using [native] assuming you have a recent version of ClearWin+.

There is no problem with much larger arrays with older SIMPLEPLOT method, the problem is that it does not like values less then 1e-22 (or 1e-30) or more then 1e22 as i remember, it simply crashes or plots nothing. Often very small numbers are not important, so if the numbers are smaller then 1e-22 just keep them 1e-22. But better switch to native PL, the more people polish it with their back the better compiler

This compilation access error is NOT limited to SIMPLEPLOT or CLEARWIN or %pl. I will try to furnish another example which does not involve plotting.

Thank you for your responses, John, Paul and Dan. I am now looking into plotting and have questions about the 4 or so different methods. You've provided useful information. As noted above, this error is not just with %pl or plotting.

Dan the K

This compilation access error is NOT limited to SIMPLEPLOT or CLEARWIN or %pl. I will try to furnish another example which does not involve plotting.

Thank you for your responses, John, Paul and Dan. I am now looking into plotting and have questions about the 4 or so different methods. You've provided useful information. As noted above, this error is not just with %pl or plotting.

Dan the K

Here is one of the first programs I wrote which, when compiled, generated the same access error:

[from Errorlog] Access violation: The instruction at address 100181b6 attempted to read from location 00000000 100181a0 _form(<ptr>char,<ptr>char,int,enumÄlogical,enumÄlogical,enumÄlogical,int) [+0016] 1001848a _sprintf(<ptr>char,<ptr>constÄchar,<ptr>char) [+0db7] 10019cbf sprintf [+0021] 004a6e93 describe_type(<ptr>structÄtype_definition,<ptr>structÄscoped_entity)#3A [+0475] 004a74a5 describe(<ptr>structÄscoped_entity)#3A [+00fe] 004a786c generate_xref_info(<ptr>structÄscope) [+01ca] 00417af9 end_function(int) [+11fc] 004199a4 parse_end_statement(<ptr>char,int,<ref>int) [+0c2f] eax=00000000 ebx=00000017 ecx=ffffffff edx=00000000 esi=00abb0dc edi=00000000 ebp=03d4e3d0 esp=03d4e3a4 IOPL=0 ds=002b es=002b fs=0053 gs=002b cs=0023 ss=002b flgs=00210246 [NC EP ZR SN DN NV] 0360/1020 TSTK=2 [ ] 100181b6 repne
100181b7 scasb

  WINAPP                                            !for CLEARWIN
  PROGRAM Main
  USE CLRWIN$

! ! Fortran 95, Martin Counihan ! Chapter 7, page 109, Introducing external procedures ! Section 7.4, Exercises 7.B, page 119 ! Exercise 7.B8 ! ! 'From two successive complex numbers z1 and z2, a third is ! generated by taking ! z3 = 0.5*(z1+z2) + c*(z1-z2) ! where c is an imaginary constant. Hence, an indefinite sequence of ! complex numbers can be generated, given two to start things off. ! Write a program to model what is going on and investigate the ! convergence of the sequence for different values of c.' ! ! Interpret this as c is strictly imaginary: c0i, c0 is entered by ! the user, z10 and z20 are randomly generated, and Function zthree ! is the called function which generates z3. ! ! The function will be zthree(z1, z2, c) ! COMPLEX:: zthree, c, z1, z2, z3(250) INTEGER:: i REAL:: c0 !c = ic0 REAL:: Rz12(2,2) !Rz12 randomly generates z1 and z2 REAL:: Converge !|z3(i)-z3(i-1)| ! ! Eps = EPSILON(1.) ReadIn: DO WRITE(,) 'Please enter a real number c. ic will be the & &complex coefficient used to generate z3 from z1 and z2 by & &z3 = 0.5(z1+z2) + c*(z1-z2).' READ(,) c0 c = c0 * (0,1.) ! z1 and z2 will be randomly generated CALL RANDOM_SEED CALL RANDOM_NUMBER(Rz12) z1 = CMPLX(Rz12(1,1),Rz12(1,2)) z2 = CMPLX(Rz12(2,1),Rz12(2,2)) iLoop: DO i=1,250 z3(i) = zthree(z1, z2, c) !Generate the next ! !element of the sequence InitValue: IF (i.EQ.1) THEN ! !Can't consider Cauchy convergence for z3(1) WRITE(,) 'z3(', i, ') = ' ELSE IF (i.GE.2) THEN InitValue ! !consider Cauchy convergence Converge = ABS(z3(i)-z3(i-1)) WRITE(,) 'z3(', i, ') = ', z3(i), '|z3(i)-z3(i-1)| = ', Converge PAUSE END IF InitValue ! !Rearrange z1, z2, z3 z1 = z2 z2 = z3(i) END DO iLoop
END DO Readin ! END PROGRAM Main

Note that this has nothing to do with %pl or plotting. I think it’s a defective compiler. The error occurs whenever an array is dimensioned as over (250). It does not occur in this example if I dimension z3 as (125). Ditto for yarr1 in the original example.

Dan the K.

What are ? USE CLRWIN$ zthree(z1, z2, c) !Generate the next

I can not get your program to run at all.

CLRWIN$ is not used. zthree is missing.

Guessed zthree and modified code for >250. My changes were to make it easier to test. Can't see how 250 is the issue, unless you did not change dimension.

PROGRAM Main 
!!??  USE CLRWIN$ 
 ! 
 ! Fortran 95, Martin Counihan 
 ! Chapter 7, page 109, Introducing external procedures 
 ! Section 7.4, Exercises 7.B, page 119 
 ! Exercise 7.B8 
 ! 
 ! 'From two successive complex numbers z1 and z2, a third is 
 ! generated by taking 
 ! z3 = 0.5*(z1+z2) + c*(z1-z2) 
 ! where c is an imaginary constant. Hence, an indefinite sequence of 
 ! complex numbers can be generated, given two to start things off. 
 ! Write a program to model what is going on and investigate the 
 ! convergence of the sequence for different values of c.' 
 ! 
 ! Interpret this as c is strictly imaginary: c0*i, c0 is entered by 
 ! the user, z10 and z20 are randomly generated, and Function zthree 
 ! is the called function which generates z3. 
 ! 
 ! The function will be zthree(z1, z2, c) 
 ! 
    integer, parameter :: n = 500
    COMPLEX*8 :: zthree, c, z1, z2, z3(n) 
    INTEGER :: i 
    REAL*8    :: c0         !c = i*c0 
    REAL*8    :: Rz12(2,2)  !Rz12 randomly generates z1 and z2 
    REAL*8    :: Converge   !|z3(i)-z3(i-1)| 
 ! 
 ! Eps = EPSILON(1.) 
   ReadIn: DO 
      WRITE(*,*) 'Please enter a real number c. i*c will be the & 
                 &complex coefficient used to generate z3 from z1 and z2 by & 
                 &z3 = 0.5*(z1+z2) + c*(z1-z2).' 
      READ(*,*) c0 
      if ( c0 < 0 ) exit
      c = c0 * (0.,1.) 
 ! z1 and z2 will be randomly generated 
      CALL RANDOM_SEED 
      CALL RANDOM_NUMBER(Rz12) 
      z1 = CMPLX(Rz12(1,1),Rz12(1,2)) 
      z2 = CMPLX(Rz12(2,1),Rz12(2,2)) 
 iLoop: DO i=1,n 
            z3(i) = zthree(z1, z2, c) !Generate the next 
 ! !element of the sequence 
 InitValue: IF (i.EQ.1) THEN 
 ! !Can't consider Cauchy convergence for z3(1) 
               WRITE(*,*) 'z3(', i, ') = ' 
            ELSE IF (i.GE.2) THEN InitValue 
 ! !consider Cauchy convergence 
               Converge = ABS(z3(i)-z3(i-1)) 
               WRITE(*,*) 'z3(', i, ') = ', z3(i), '|z3(i)-z3(i-1)| = ', Converge 
               if ( abs(converge) < 1.e-8 ) exit
!               PAUSE 
            END IF InitValue 
 ! !Rearrange z1, z2, z3 
            z1 = z2 
            z2 = z3(i) 
         END DO iLoop 
     END DO Readin 
 ! 
 END PROGRAM Main 

 function zthree (z1,z2, c)
    COMPLEX*8 :: zthree, c, z1, z2

  zthree = 0.5d0*(z1+z2) + c*(z1-z2)

end function zthree