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HPF%20(High%20Performance%20Fortran)

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int A(10), B(10), C(10) int D(50), E(100), F(100) int max. int G(100), H(100,100) A(1:8) = B(1:8) C(2:9) D = E(1:100:2) F(2:99:2) max = MAXVAL( G(1:100:10) ... – PowerPoint PPT presentation

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Title: HPF%20(High%20Performance%20Fortran)

1

HPF (High Performance Fortran)

2
What is HPF?

HPF is a standard for data-parallel programming.
Extends Fortran-77 or Fortran-90.
Similar extensions exist for C and C, but
Fortran is really the focus.

3
Principle of HPF

Extending sequential language with data
distribution directives.
Data distribution directives specify on which
processor a certain part of an array should
reside.
Compiler then produces
parallel program,
communication between the processes.

4
What the Standard Says

Can be used with both Fortran-77 and Fortran-90.
Distribution directives are just a hint, compiler
can ignore them.
HPF can be used on both shared memory and
distributed memory hardware platforms.

5
In Commercial Use

HPF is always used with Fortran-90.
Distribution directives are a must.
HPF used on both shared memory and distributed
memory platforms.
But the truth is that the language was really
meant for distributed memory platforms.

6
Not to Confuse You

We will discuss commercial use
Fortran-90
Concurrency extensions to Fortran-90 in HPF.
HPF data distribution directives.
How HPF maps to a distributed memory platform.
Afterwards, we will discuss what the standard
allows in addition.

7
Fortran-90

Fortran a number of array features.
Scalar operations are extended to arrays.
Intrinsic functions are extended to arrays.
Additional array-based intrinsic functions.

8
Array Assignment

Scalar assignment
integer a, b, c
a b c
Array assignment
integer A(10,10), B(10,10), C(10,10)
A B C

9
Requirements for Array Assignment

Arrays must be comformable
have the same number of dimensions, and
have the same size in each dimension.
One major exception for scalar is allowed
integer A(10,10), B(10,10), c
A B c

10
Intrinsic Functions Extended to Arrays

integer A(10,10), B(10,10)
A SQRT(A)
B ABS(A)

11
Additional Array Intrinsic Functions

MAXVAL, MINVAL
MAXLOC, MINLOC
return array of indices
SUM, PRODUCT
MATMUL, DOT_PRODUCT, TRANSPOSE

12
Examples

real A(100,100), B(100), s
int i(1), j(2)
s SUM(A)
i MAXLOC(B)
j MINLOC(A)
C DOT_PRODUCT(B, A)

13
Array Sections

array( lower_bound upper_bound stride )
Refers to the section of the array between
lower_bound and upper_bound, with an optional
stride specified.
Multiple dimensions may be specified, with the
obvious meaning.
Array sections may be used wherever arrays may be
used.

14
Examples

int A(10), B(10), C(10)
int D(50), E(100), F(100)
int max
int G(100), H(100,100)
A(18) B(18) C(29)
D E(11002) F(2992)
max MAXVAL( G(110010) )
max MINVAL( H(1100, 150) )

15
Semantics of Array Assignments

First, the entire right hand side is evaluated.
Then, assignments are made to the left hand side.

16
Example

int A(4) 7, 8, 12, 14
A(23) A(12)
gt results in A being 7, 7, 8, 14
gt not 7, 7, 7, 14

17
Sequential/Parallel Fortran-90

Fortran-90 is a sequential language.
However, its array assignment semantics makes it
easy to parallelize it (automatically).

18
Not Perfect, Though (1 of 2)

do i 1,100
X(i,i) 0.0
enddo
Obviously parallelizable.
Not expressible as a Fortran-90 array assignment
(only regular sections).

19
Not Perfect, Though (2 of 2)

int D(50), E(100), F(100)
D E(11002) F(2992)
is correct, but
int D(100), E(100), F(100)
D E(11002) F(2992)
is not, because array D is not conformable.

20
HPF Additional Expressions of Parallelism

FORALL array assignment.
INDEPENDENT construct.

21
FORALL Array Assignment

FORALL( subscript lower_bound upper_bound
stride, mask) array-assignment
Execute all iterations of the subscript loop in
parallel for the given set of indices, where mask
is true.
May have multiple dimensions.
Same semantics first compute right hand side,
then assign to left hand side.
Only one assignment to particular element (not
checked by the compiler!).

22
Examples (1 of 3)