J3/04-129

Date:    13 Dec. 2003
To:      J3
From:    Dan Nagle
Subject: HPF Intrinsics


This proposal is to incorporate the HPF operations
ceiling division and ceiling remainder.

Number:

Title: Ceiling Division and Ceiling Remainder

Submitted By: J3

Status: For Consideration

References: HPF (See, e.g., _The High Performance Fortran
                Handbook_, Koelbel, C. H., et al. page 107)
            Also, see Sections 13.7.80 MOD, 13.7.81 MODULO

Basic Functionality: Ceiling Division is a kind of integer devision,
                     rather than truncating the quotient, it is
                     rounded upwards.  Ceiling Remainder is
                     (always zero or negative) remainder after
                     Ceiling Division.

Rationale:  When dividing something into groups, one often has
            a size characteristic of the containers used.  For
            example, one might ask how many egg cartons is needed to hold
            an arbitrary number of eggs.  To hold 42 eggs, one
            needs 4 cartons (which can hold a dozen eggs each).
            This problem is often encountered when a parallel program
            assigns computations to processors.  Ceiling Division
            is the operation providing the answer.  Ceiling Remainder
            is the number of empty spaces left over, expressed as
            a negative number (so number = quotient * divisor + remainder
            always holds).

Estimated Impact: These are two more intrinsics to be supported.

Detailed Specification:  Add two new intrinsics: CDIV and CREM.

                         CDIV( A, P)  A, P are integers of any kind

                         Result is A/P if the remainder is zero,
                         otherwise the result is A/P + 1

                         CREM( A, P)  A, P are integers of any kind

                         Result is A - CDIV( A, P) * P

                         Example:

                         type( bigwork_t), dimension( n) :: work_items

                         work_per_processor = cdiv( n, number_of_processors)

History: