1: /*
  2:        Low cost access to a system time. This, in general, should not be included in user programs.
  3: */
  4: #pragma once

  6: #include <petscsys.h>

  8: /* SUBMANSEC = Sys */

 10: PETSC_EXTERN PetscErrorCode PetscGetCPUTime(PetscLogDouble *);

 12: /* Global counters */
 13: PETSC_EXTERN PetscLogDouble petsc_BaseTime;

 15: /*MC
 16:    PetscTime - Returns the current time from some base time in the past in seconds.

 18:    Synopsis:
 19: #include <petsctime.h>
 20:     PetscErrorCode PetscTime(PetscLogDouble *v)

 22:    Not Collective

 24:    Output Parameter:
 25: .  v - time counter

 27:    Usage:
 28: .vb
 29:      PetscLogDouble v;
 30:      PetscTime(&v);
 31:      .... perform some calculation ...
 32:      printf("Time for operation %g\n",v);
 33: .ve

 35:    Level: developer

 37:    Note:
 38:    Since the PETSc libraries incorporate timing of phases and operations, we do not recommend ever using `PetscTime()`.
 39:    The options database command  `-log_view` activates PETSc library timing.
 40:    See `PetscLogStageRegister()`, `PetscLogEventRegister()`, `PetscLogEventBegin()`, `PetscLogEventEnd()` for how to register
 41:    stages and events in application codes.

 43: .seealso: `PetscTimeSubtract()`, `PetscTimeAdd()`, `PetscLogStageRegister()`, `PetscLogEventRegister()`, `PetscLogEventBegin()`, `PetscLogEventEnd()`
 44: M*/

 46: /*MC
 47:    PetscTimeSubtract - Subtracts the current time (in seconds) from the value `v`.

 49:    Synopsis:
 50: #include <petsctime.h>
 51:     PetscErrorCode PetscTimeSubtract(PetscLogDouble *v)

 53:    Not Collective

 55:    Input Parameter:
 56: .  v - time counter

 58:    Output Parameter:
 59: .  v - time counter (`v` = `v` - current time)

 61:    Level: developer

 63:    Note:
 64:    Since the PETSc libraries incorporate timing of phases and operations, we do not always recommend using `PetscTimeSubtract()`.
 65:    The options database command  `-log_view` activates PETSc library timing.
 66:    See `PetscLogStageRegister()`, `PetscLogEventRegister()`, `PetscLogEventBegin()`, `PetscLogEventEnd()` for how to register
 67:    stages and events in application codes.

 69: .seealso: `PetscTime()`, `PetscTimeAdd()`, `PetscLogStageRegister()`, `PetscLogEventRegister()`, `PetscLogEventBegin()`, `PetscLogEventEnd()`
 70: M*/

 72: /*MC
 73:    PetscTimeAdd - Adds the current time (in seconds) to the value `v`.

 75:    Synopsis:
 76: #include <petsctime.h>
 77:     PetscErrorCode PetscTimeAdd(PetscLogDouble *v)

 79:    Not Collective

 81:    Input Parameter:
 82: .  v - time counter

 84:    Output Parameter:
 85: .  v - time counter (`v` = `v` + current time)

 87:    Level: developer

 89:    Note:
 90:    Since the PETSc libraries incorporate timing of phases and operations,  we do not ever recommend using `PetscTimeAdd()`.
 91:    The options database command `-log_view` activates PETSc library timing.

 93: .seealso: `PetscTime()`, `PetscTimeSubtract()`, `PetscLogStageRegister()`, `PetscLogEventRegister()`, `PetscLogEventBegin()`, `PetscLogEventEnd()`
 94: M*/

 96: static inline PetscErrorCode PetscTime(PetscLogDouble *v)
 97: {
 98:   *v = MPI_Wtime();
 99:   return PETSC_SUCCESS;
100: }

102: static inline PetscErrorCode PetscTimeSubtract(PetscLogDouble *v)
103: {
104:   *v -= MPI_Wtime();
105:   return PETSC_SUCCESS;
106: }

108: static inline PetscErrorCode PetscTimeAdd(PetscLogDouble *v)
109: {
110:   *v += MPI_Wtime();
111:   return PETSC_SUCCESS;
112: }