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Fernando Magno Quintao Pereira - One of the best experts on this subject based on the ideXlab platform.
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aliased register allocation for straight line programs is np complete
International Colloquium on Automata Languages and Programming, 2007Co-Authors: Jonathan K Lee, Jens Palsberg, Fernando Magno Quintao PereiraAbstract:Register allocation is NP-complete in general but can be solved in linear time for straight-line programs where each variable has at most one Definition Point if the bank of registers is homogeneous. In this paper we study registers which may alias: an aliased register can be used both independently or in combination with an adjacent register. Such registers are found in commonly-used architectures such as x86, the HP PA-RISC, the Sun SPARC processor, and MIPS floating Point. In 2004, Smith, Ramsey, and Holloway presented the best algorithm for aliased register allocation so far; their algorithm is based on a heuristic for coloring of general graphs. Most architectures with register aliasing allow only aligned registers to be combined: for example, the low-address register must have an even number. Open until now is the question of whether working with restricted classes of programs can improve the complexity of aliased register allocation with alignment restrictions. In this paper we show that aliased register allocation with alignment restrictions for straight-line programs is NP-complete.
Jonathan K Lee - One of the best experts on this subject based on the ideXlab platform.
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aliased register allocation for straight line programs is np complete
International Colloquium on Automata Languages and Programming, 2007Co-Authors: Jonathan K Lee, Jens Palsberg, Fernando Magno Quintao PereiraAbstract:Register allocation is NP-complete in general but can be solved in linear time for straight-line programs where each variable has at most one Definition Point if the bank of registers is homogeneous. In this paper we study registers which may alias: an aliased register can be used both independently or in combination with an adjacent register. Such registers are found in commonly-used architectures such as x86, the HP PA-RISC, the Sun SPARC processor, and MIPS floating Point. In 2004, Smith, Ramsey, and Holloway presented the best algorithm for aliased register allocation so far; their algorithm is based on a heuristic for coloring of general graphs. Most architectures with register aliasing allow only aligned registers to be combined: for example, the low-address register must have an even number. Open until now is the question of whether working with restricted classes of programs can improve the complexity of aliased register allocation with alignment restrictions. In this paper we show that aliased register allocation with alignment restrictions for straight-line programs is NP-complete.
Jens Palsberg - One of the best experts on this subject based on the ideXlab platform.
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aliased register allocation for straight line programs is np complete
International Colloquium on Automata Languages and Programming, 2007Co-Authors: Jonathan K Lee, Jens Palsberg, Fernando Magno Quintao PereiraAbstract:Register allocation is NP-complete in general but can be solved in linear time for straight-line programs where each variable has at most one Definition Point if the bank of registers is homogeneous. In this paper we study registers which may alias: an aliased register can be used both independently or in combination with an adjacent register. Such registers are found in commonly-used architectures such as x86, the HP PA-RISC, the Sun SPARC processor, and MIPS floating Point. In 2004, Smith, Ramsey, and Holloway presented the best algorithm for aliased register allocation so far; their algorithm is based on a heuristic for coloring of general graphs. Most architectures with register aliasing allow only aligned registers to be combined: for example, the low-address register must have an even number. Open until now is the question of whether working with restricted classes of programs can improve the complexity of aliased register allocation with alignment restrictions. In this paper we show that aliased register allocation with alignment restrictions for straight-line programs is NP-complete.
Hiroki Yamashita - One of the best experts on this subject based on the ideXlab platform.
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Spatial joint constraints for the absolute nodal coordinate formulation using the non-generalized intermediate coordinates
Multibody System Dynamics, 2011Co-Authors: Hiroyuki Sugiyama, Hiroki YamashitaAbstract:In this investigation, a systematic procedure that can be used for modeling joint constraints for the absolute nodal coordinate formulation is developed. To this end, the non-generalized intermediate coordinates are introduced to derive a mapping between the generalized gradient coordinates and the non-generalized rotation parameters. With this mapping, a wide variety of joint constraints can be defined for the absolute nodal coordinate formulation in terms of the non-generalized reference coordinates and, therefore, existing well-developed constraint libraries formulated for the rigid body reference coordinates can be directly employed without significant modifications in existing codes. Furthermore, in order to define a rigid surface at the joint Definition Point, a set of orthonormality conditions is imposed on the gradient coordinates. This leads to not only accurate modeling of interface to mechanical joint, but also a simpler Definition of the joint coordinate system obtained by the orthonormal gradient vectors. For this reason, a simpler form of constraint Jacobian and quadratic velocity vectors can be obtained as compared to those of the existing approach which requires the use of highly nonlinear joint coordinate system. A systematic procedure for eliminating the non-generalized coordinates and the dependent Lagrange multipliers associated with the coordinate mapping equations from the equations of motion is presented. As a result, a standard augmented form of the equations of motion can be obtained in terms of the generalized coordinates only. Several numerical examples are presented in order to demonstrate the use of the joint constraint formulation developed in this investigation.
Hiroyuki Sugiyama - One of the best experts on this subject based on the ideXlab platform.
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Spatial joint constraints for the absolute nodal coordinate formulation using the non-generalized intermediate coordinates
Multibody System Dynamics, 2011Co-Authors: Hiroyuki Sugiyama, Hiroki YamashitaAbstract:In this investigation, a systematic procedure that can be used for modeling joint constraints for the absolute nodal coordinate formulation is developed. To this end, the non-generalized intermediate coordinates are introduced to derive a mapping between the generalized gradient coordinates and the non-generalized rotation parameters. With this mapping, a wide variety of joint constraints can be defined for the absolute nodal coordinate formulation in terms of the non-generalized reference coordinates and, therefore, existing well-developed constraint libraries formulated for the rigid body reference coordinates can be directly employed without significant modifications in existing codes. Furthermore, in order to define a rigid surface at the joint Definition Point, a set of orthonormality conditions is imposed on the gradient coordinates. This leads to not only accurate modeling of interface to mechanical joint, but also a simpler Definition of the joint coordinate system obtained by the orthonormal gradient vectors. For this reason, a simpler form of constraint Jacobian and quadratic velocity vectors can be obtained as compared to those of the existing approach which requires the use of highly nonlinear joint coordinate system. A systematic procedure for eliminating the non-generalized coordinates and the dependent Lagrange multipliers associated with the coordinate mapping equations from the equations of motion is presented. As a result, a standard augmented form of the equations of motion can be obtained in terms of the generalized coordinates only. Several numerical examples are presented in order to demonstrate the use of the joint constraint formulation developed in this investigation.