fpakc/src/modules/common/moduleRandom.f90
JGonzalez 626e970d82 Some progress
Fixed an issue with random integer numbers.
Cylindrical coordinates are not perfect yet:
  - Box (cylinder) with initial constant density loses particles at r =
    0
  - Injection density still low in r = 0
2024-07-06 19:14:44 +02:00

94 lines
2 KiB
Fortran

MODULE moduleRandom
!Interface for random number generator
INTERFACE random
MODULE PROCEDURE randomReal, randomRealAB, randomIntAB
END INTERFACE random
CONTAINS
!Returns a Real random number between 0 and 1
FUNCTION randomReal() RESULT(rnd)
IMPLICIT NONE
REAL(8):: rnd
rnd = 0.D0
CALL RANDOM_NUMBER(rnd)
END FUNCTION randomReal
!Returns a Real random number between a and b
FUNCTION randomRealAB(a, b) RESULT(rnd)
IMPLICIT NONE
REAL(8), INTENT(in):: a, b
REAL(8):: rnd
REAL(8):: rnd01 !random real between 0 and 1
rnd = 0.D0
CALL RANDOM_NUMBER(rnd01)
rnd = (b - a) * rnd01 + a
END FUNCTION randomRealAB
!Returns an Integer random numnber between a and b
FUNCTION randomIntAB(a, b) RESULT(rnd)
IMPLICIT NONE
INTEGER, INTENT(in):: a, b
INTEGER:: rnd
REAL(8):: rnd01
rnd = 0
CALL RANDOM_NUMBER(rnd01)
rnd = a + FLOOR((b+1-a)*rnd01)
END FUNCTION randomIntAB
!Returns a random number in a Maxwellian distribution of mean 0 and width 1
FUNCTION randomMaxwellian() RESULT(rnd)
USE moduleConstParam, ONLY: PI
IMPLICIT NONE
REAL(8):: rnd
REAL(8):: x, y
rnd = 0.D0
x = 0.D0
DO WHILE (x == 0.D0)
CALL RANDOM_NUMBER(x)
END DO
CALL RANDOM_NUMBER(y)
rnd = DSQRT(-2.D0*DLOG(x))*DCOS(2.D0*PI*y)
END FUNCTION randomMaxwellian
!Returns a random number weighted with the cumWeight array
FUNCTION randomWeighted(cumWeight, sumWeight) RESULT(rnd)
IMPLICIT NONE
REAL(8), INTENT(in):: cumWeight(1:)
REAL(8), INTENT(in):: sumWeight
REAL(8):: rnd0b
INTEGER:: rnd, i
rnd0b = random()
i = 1
DO
IF (rnd0b <= cumWeight(i)/sumWeight) THEN
rnd = i
EXIT
ELSE
i = i +1
END IF
END DO
! rnd = MINLOC(DABS(rnd0b - cumWeight), 1)
END FUNCTION randomWeighted
END MODULE moduleRandom