2: #include <petscsys.h>

  4: /*@
  5:     PetscSplitOwnershipBlock - Given a global (or local) length determines a local
  6:         (or global) length via a simple formula. Splits so each processors local size
  7:         is divisible by the block size.

  9:    Collective (if N is PETSC_DECIDE)

 11:    Input Parameters:
 12: +    comm - MPI communicator that shares the object being divided
 13: .    bs - block size
 14: .    n - local length (or PETSC_DECIDE to have it set)
 15: -    N - global length (or PETSC_DECIDE)

 17:   Level: developer

 19:    Notes:
 20:      n and N cannot be both PETSC_DECIDE

 22:      If one processor calls this with N of PETSC_DECIDE then all processors
 23:      must, otherwise the program will hang.

 25: .seealso: PetscSplitOwnership()

 27: @*/
 28: PetscErrorCode  PetscSplitOwnershipBlock(MPI_Comm comm,PetscInt bs,PetscInt *n,PetscInt *N)
 29: {
 31:   PetscMPIInt    size,rank;

 34:   if (*N == PETSC_DECIDE && *n == PETSC_DECIDE) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_INCOMP,"Both n and N cannot be PETSC_DECIDE");

 36:   if (*N == PETSC_DECIDE) {
 37:     if (*n % bs != 0) SETERRQ2(PETSC_COMM_SELF,PETSC_ERR_ARG_INCOMP,"local size %D not divisible by block size %D",*n,bs);
 38:     MPIU_Allreduce(n,N,1,MPIU_INT,MPI_SUM,comm);
 39:   } else if (*n == PETSC_DECIDE) {
 40:     PetscInt Nbs = *N/bs;
 41:     MPI_Comm_size(comm,&size);
 42:     MPI_Comm_rank(comm,&rank);
 43:     *n   = bs*(Nbs/size + ((Nbs % size) > rank));
 44:   }
 45:   return(0);
 46: }

 48: /*@
 49:     PetscSplitOwnership - Given a global (or local) length determines a local
 50:         (or global) length via a simple formula

 52:    Collective (if n or N is PETSC_DECIDE)

 54:    Input Parameters:
 55: +    comm - MPI communicator that shares the object being divided
 56: .    n - local length (or PETSC_DECIDE to have it set)
 57: -    N - global length (or PETSC_DECIDE)

 59:   Level: developer

 61:    Notes:
 62:      n and N cannot be both PETSC_DECIDE

 64:      If one processor calls this with n or N of PETSC_DECIDE then all processors
 65:      must. Otherwise, an error is thrown in debug mode while the program will hang
 66:      in optimized (i.e. configured --with-debugging=0) mode.

 68: .seealso: PetscSplitOwnershipBlock()

 70: @*/
 71: PetscErrorCode  PetscSplitOwnership(MPI_Comm comm,PetscInt *n,PetscInt *N)
 72: {
 74:   PetscMPIInt    size,rank;

 77:   if (*N == PETSC_DECIDE && *n == PETSC_DECIDE) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_INCOMP,"Both n and N cannot be PETSC_DECIDE\n  likely a call to VecSetSizes() or MatSetSizes() is wrong.\nSee https://petsc.org/release/faq/#split-ownership");
 78:   if (PetscDefined(USE_DEBUG)) {
 79:     PetscMPIInt l[2],g[2];
 80:     l[0] = (*n == PETSC_DECIDE) ? 1 : 0;
 81:     l[1] = (*N == PETSC_DECIDE) ? 1 : 0;
 82:     MPI_Comm_size(comm,&size);
 83:     MPIU_Allreduce(l,g,2,MPI_INT,MPI_SUM,comm);
 84:     if (g[0] && g[0] != size) SETERRQ(comm,PETSC_ERR_ARG_INCOMP,"All processes must supply PETSC_DECIDE for local size");
 85:     if (g[1] && g[1] != size) SETERRQ(comm,PETSC_ERR_ARG_INCOMP,"All processes must supply PETSC_DECIDE for global size");
 86:   }

 88:   if (*N == PETSC_DECIDE) {
 89:     PetscInt64 m = *n, M;
 90:     MPIU_Allreduce(&m,&M,1,MPIU_INT64,MPI_SUM,comm);
 91:     if (M > PETSC_MAX_INT) SETERRQ1(comm,PETSC_ERR_INT_OVERFLOW,"Global size overflow %" PetscInt64_FMT ". You may consider ./configure PETSc with --with-64-bit-indices for the case you are running", M);
 92:     else *N = (PetscInt)M;
 93:   } else if (*n == PETSC_DECIDE) {
 94:     MPI_Comm_size(comm,&size);
 95:     MPI_Comm_rank(comm,&rank);
 96:     *n   = *N/size + ((*N % size) > rank);
 97:   } else if (PetscDefined(USE_DEBUG)) {
 98:     PetscInt tmp;
 99:     MPIU_Allreduce(n,&tmp,1,MPIU_INT,MPI_SUM,comm);
100:     if (tmp != *N) SETERRQ3(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Sum of local lengths %D does not equal global length %D, my local length %D\n  likely a call to VecSetSizes() or MatSetSizes() is wrong.\nSee https://petsc.org/release/faq/#split-ownership",tmp,*N,*n);
101:   }
102:   return(0);
103: }

105: /*@
106:     PetscSplitOwnershipEqual - Given a global (or local) length determines a local
107:         (or global) length via a simple formula, trying to have all local lengths equal

109:    Collective (if n or N is PETSC_DECIDE)

111:    Input Parameters:
112: +    comm - MPI communicator that shares the object being divided
113: .    n - local length (or PETSC_DECIDE to have it set)
114: -    N - global length (or PETSC_DECIDE)

116:    Level: developer

118:    Notes:
119:      This is intended to be used with MATSCALAPACK, where the local size must
120:      be equal in all processes (except possibly the last one). For instance,
121:      the local sizes when spliting N=50 with 6 processes are 9,9,9,9,9,5

123:      n and N cannot be both PETSC_DECIDE

125:      If one processor calls this with n or N of PETSC_DECIDE then all processors
126:      must. Otherwise, an error is thrown in debug mode while the program will hang
127:      in optimized (i.e. configured --with-debugging=0) mode.

129: .seealso: PetscSplitOwnership(), PetscSplitOwnershipBlock()

131: @*/
132: PetscErrorCode  PetscSplitOwnershipEqual(MPI_Comm comm,PetscInt *n,PetscInt *N)
133: {
135:   PetscMPIInt    size,rank;

138:   if (*N == PETSC_DECIDE && *n == PETSC_DECIDE) SETERRQ(PETSC_COMM_SELF,PETSC_ERR_ARG_INCOMP,"Both n and N cannot be PETSC_DECIDE");
139:   if (PetscDefined(USE_DEBUG)) {
140:     PetscMPIInt l[2],g[2];
141:     l[0] = (*n == PETSC_DECIDE) ? 1 : 0;
142:     l[1] = (*N == PETSC_DECIDE) ? 1 : 0;
143:     MPI_Comm_size(comm,&size);
144:     MPIU_Allreduce(l,g,2,MPI_INT,MPI_SUM,comm);
145:     if (g[0] && g[0] != size) SETERRQ(comm,PETSC_ERR_ARG_INCOMP,"All processes must supply PETSC_DECIDE for local size");
146:     if (g[1] && g[1] != size) SETERRQ(comm,PETSC_ERR_ARG_INCOMP,"All processes must supply PETSC_DECIDE for global size");
147:   }

149:   if (*N == PETSC_DECIDE) {
150:     PetscInt64 m = *n, M;
151:     MPIU_Allreduce(&m,&M,1,MPIU_INT64,MPI_SUM,comm);
152:     if (M > PETSC_MAX_INT) SETERRQ1(comm,PETSC_ERR_INT_OVERFLOW,"Global size overflow %" PetscInt64_FMT ". You may consider ./configure PETSc with --with-64-bit-indices for the case you are running", M);
153:     else *N = (PetscInt)M;
154:   } else if (*n == PETSC_DECIDE) {
155:     MPI_Comm_size(comm,&size);
156:     MPI_Comm_rank(comm,&rank);
157:     *n = *N/size;
158:     if (*N % size) {
159:       if ((rank+1)*(*n+1)<=*N)  *n = *n+1;
160:       else if (rank*(*n+1)<=*N) *n = *N-rank*(*n+1);
161:       else *n = 0;
162:     }
163:   } else if (PetscDefined(USE_DEBUG)) {
164:     PetscInt tmp;
165:     MPIU_Allreduce(n,&tmp,1,MPIU_INT,MPI_SUM,comm);
166:     if (tmp != *N) SETERRQ3(PETSC_COMM_SELF,PETSC_ERR_ARG_SIZ,"Sum of local lengths %D does not equal global length %D, my local length %D",tmp,*N,*n);
167:   }
168:   return(0);
169: }