<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; line-break: after-white-space;" class=""><div class=""><br class=""></div> I believe I have fixed the bug in the branch <b style="color: rgb(200, 20, 201); font-family: Menlo; font-size: 14px;" class="">barry/2021-11-26/fix-petscsfgetgraph-fortran/release </b><a href="https://gitlab.com/petsc/petsc/-/merge_requests/4605" class="">https://gitlab.com/petsc/petsc/-/merge_requests/4605</a><br class=""><div class=""><br class=""></div><div class=""> See <span style="font-family: Menlo; font-size: 14px;" class="">src/vec/is/sf/tutorials/ex1f.F90 for how to check if the returned value is a FORTRAN_NULL_INTEGER</span></div><div class=""><span style="font-family: Menlo; font-size: 14px;" class=""><br class=""></span></div><div class=""> Barry</div><div class=""><br class=""><div><br class=""><blockquote type="cite" class=""><div class="">On Nov 24, 2021, at 3:19 AM, 袁煕 <<a href="mailto:yuanxi@advancesoft.jp" class="">yuanxi@advancesoft.jp</a>> wrote:</div><br class="Apple-interchange-newline"><div class=""><div dir="ltr" class="">Thank you for the clarification. I am looking forward to this bug fix.<br class=""><div class=""><br class=""></div><div class="">Yuan</div></div><br class=""><div class="gmail_quote"><div dir="ltr" class="gmail_attr">2021年11月22日(月) 23:17 Barry Smith <<a href="mailto:bsmith@petsc.dev" class="">bsmith@petsc.dev</a>>:<br class=""></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div style="overflow-wrap: break-word;" class=""><div class=""><br class=""></div> The address of PETSC_NULL_INTEGER is not 0, it in some common block location. PETSC_NULL_INTEGER should not be used in the form <div class="">if idx == PETSC_NULL_INTEGER, it is only to be used as an argument to a PETSc function that on the C side can take a NULL (integer) argument.</div><div class=""><br class=""></div><div class=""> As I noted before whoever wrote the incorrect petscsfgetgraph_ Fortran wrapper needs to fix it.</div><div class=""><br class=""></div><div class=""> Barry</div><div class=""><br class=""><div class=""><br class=""><blockquote type="cite" class=""><div class="">On Nov 21, 2021, at 8:05 PM, 袁煕 <<a href="mailto:yuanxi@advancesoft.jp" target="_blank" class="">yuanxi@advancesoft.jp</a>> wrote:</div><br class=""><div class=""><div dir="ltr" class=""><div class="">Thank you very much.</div><div class=""><br class=""></div>The NULL pointer could be identified by if( loc(gmine)==PETSC_NULL_INTEGER) as above <a class="gmail_plusreply" id="gmail-m_-789483520662939723plusReplyChip-0" href="mailto:mfadams@lbl.gov" target="_blank">@Mark Adams</a> suggested. However, It seems that there is a memory leak here? <div class=""><br class=""></div><div class="">Yuan</div></div><br class=""><div class="gmail_quote"><div dir="ltr" class="gmail_attr">2021年11月19日(金) 22:20 Barry Smith <<a href="mailto:bsmith@petsc.dev" target="_blank" class="">bsmith@petsc.dev</a>>:<br class=""></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><br class="">
it is very possible there is a bug in the Fortran interface for this function. It looks like whoever wrote the Fortran interface did not think through the special case of contiguous entries.<br class="">
<br class="">
PETSC_EXTERN void petscsfgetgraph_(PetscSF *sf,PetscInt *nroots,PetscInt *nleaves, F90Array1d *ailocal, F90Array1d *airemote, PetscErrorCode *ierr PETSC_F90_2PTR_PROTO(pilocal) PETSC_F90_2PTR_PROTO(piremote))<br class="">
{<br class="">
const PetscInt *ilocal;<br class="">
const PetscSFNode *iremote;<br class="">
<br class="">
*ierr = PetscSFGetGraph(*sf,nroots,nleaves,&ilocal,&iremote);if (*ierr) return;<br class="">
*ierr = F90Array1dCreate((void*)ilocal,MPIU_INT,1,*nleaves, ailocal PETSC_F90_2PTR_PARAM(pilocal));<br class="">
/* this creates a memory leak */<br class="">
f90arraysfnodecreate_((PetscInt*)iremote,nleaves, airemote PETSC_F90_2PTR_PARAM(piremote));<br class="">
}<br class="">
<br class="">
PetscErrorCode F90Array1dCreate(void *array,MPI_Datatype type,PetscInt start,PetscInt len,F90Array1d *ptr PETSC_F90_2PTR_PROTO(ptrd))<br class="">
{<br class="">
PetscFunctionBegin;<br class="">
if (type == MPIU_SCALAR) {<br class="">
if (!len) array = PETSC_NULL_SCALAR_Fortran;<br class="">
f90array1dcreatescalar_(array,&start,&len,ptr PETSC_F90_2PTR_PARAM(ptrd));<br class="">
} else if (type == MPIU_REAL) {<br class="">
if (!len) array = PETSC_NULL_REAL_Fortran;<br class="">
f90array1dcreatereal_(array,&start,&len,ptr PETSC_F90_2PTR_PARAM(ptrd));<br class="">
} else if (type == MPIU_INT) {<br class="">
if (!len) array = PETSC_NULL_INTEGER_Fortran;<br class="">
f90array1dcreateint_(array,&start,&len,ptr PETSC_F90_2PTR_PARAM(ptrd));<br class="">
} else if (type == MPIU_FORTRANADDR) {<br class="">
f90array1dcreatefortranaddr_(array,&start,&len,ptr PETSC_F90_2PTR_PARAM(ptrd));<br class="">
} else SETERRQ(PETSC_COMM_SELF,PETSC_ERR_SUP,"Unsupported MPI_Datatype");<br class="">
PetscFunctionReturn(0);<br class="">
}<br class="">
<br class="">
It blindly calls F90Array1dCreate() with a len = *nleaves > 0 but a NULL array ilocal then f90array1dcreateint_ must create an invalid object.<br class="">
<br class="">
Barry<br class="">
<br class="">
<br class="">
<br class="">
> On Nov 19, 2021, at 12:34 AM, 袁煕 <<a href="mailto:yuanxi@advancesoft.jp" target="_blank" class="">yuanxi@advancesoft.jp</a>> wrote:<br class="">
> <br class="">
> Dear PETSc-team,<br class="">
> <br class="">
> I am using function PetscSFGetGraph in my program like<br class="">
> -----------------------<br class="">
> call PetscSFGetGraph(sf,gnroots,gnleaves,gmine,gremote,ierr)<br class="">
> -----------------------<br class="">
> <br class="">
> In some cases, it works well. But in some cases, I encountered following error<br class="">
> ------------------<br class="">
> PETSC ERROR: Caught signal number 11 SEGV: Segmentation Violation, probably memory access out of range <br class="">
> ------------------<br class="">
> I found it is due to the action of reading gmine, which is a fortran pointer point to an array. It is reasonable because PETSc manual tells me "if returned value is NULL, it means leaves are in contiguous storage". The problem is that I cannot find if gmine is a null pointer. <br class="">
> 1) I cannot use "if (gmine==PETSC_NULL_INTEGER)" because my intel compiler would return a compile error "A scalar-valued expression is required in this context"<br class="">
> 2) When using standard style of checking a null pointer in fortran, "associated(gmine)", it returns "T". Even in cases such action of "print *, gmine(1)" would give rise to above Segmentation Violation error.<br class="">
> Is there any means to check the NULL pointer in Fortran in above cases.<br class="">
> Many thanks,<br class="">
> Yuan<br class="">
<br class="">
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