Profile inference revisited

Profile-guided optimization (PGO) is an important component in modern compilers. By allowing the compiler to leverage the program’s dynamic behavior, it can often generate substantially faster binaries. Sampling-based profiling is the state-of-the-art technique for collecting execution profiles in data-center environments. However, the lowered profile accuracy caused by sampling fully optimized binary often hurts the benefits of PGO; thus, an important problem is to overcome the inaccuracy in a profile after it is collected. In this paper we tackle the problem, which is also known as profile inference and profile rectification . We investigate the classical approach for profile inference, based on computing minimum-cost maximum flows in a control-flow graph, and develop an extended model capturing the desired properties of real-world profiles. Next we provide a solid theoretical foundation of the corresponding optimization problem by studying its algorithmic aspects. We then describe a new efficient algorithm for the problem along with its implementation in an open-source compiler. An extensive evaluation of the algorithm and existing profile inference techniques on a variety of applications, including Facebook production workloads and SPEC CPU benchmarks, indicates that the new method outperforms its competitors by significantly improving the accuracy of profile data and the performance of generated binaries.

Effects of forming velocity on micro deep drawing performance with different blank thickness

Micro deep drawing is a promising manufacturing method to produce the hollow, thin walled, cup or box like products at micro scale. Forming velocity can affect the products’ quality significantly due to the size effect, and this effect can be various with different thickness material. In this study, 30, 40, and 50 µm thickness stainless steels were annealed at 950 °C for 2 min under protection of argon gas ambient respectively. These different thickness steels were utilized in the micro deep drawing with different forming velocities. The experimental results show that, the profile accuracy and surface quality of the micro product are affected by changing the forming velocity with different thickness blanks. The micro cup has a less indentation area at the bottom and becomes rounder and more symmetrical with a thicker blank. Besides, the wrinkling phenomenon turns distinct with a thinner blank, and the earing becomes more significantly when increasing the drawing velocity or decreasing the blank thickness. When the drawing velocity or blank thickness increases, the surface of the micro cup becomes smooth and even. The experimental results are in good agreement with the simulation results, which confirms the developed finite element simulation model is applicable.

A Simulation Method for Free-form Milling Cylindrical Gears With Disc Cutters

Free-form milling is a flexible gear machining method that allows using general disc cutters to machine various gear types on a 5-axis machine tool. This paper proposes a two-dimensional simulation method for free-form milling of cylindrical gears with disc cutters. A mathematical model for free-form milling of cylindrical gears with disc cutters is constructed. By analyzing the spatial positional relationships between the cutter and the workpiece, the instantaneous contact line is derived and projected onto the gear end face, and then the projected curves are intersected to obtain the final profile. This calculation method realizes the rapid simulation of the actual cutting condition on the gear end face, which is beneficial to the judgment of machining interference and the analysis of the tooth profile accuracy during the gear machining process.

The Influence of Sheet Tilting on Forming Quality in Single Point Incremental Forming

In the CNC incremental forming process, the sheet tilting method can be used to realize the non-fracture forming of a surface with large forming angles. However, the forming effect of the formed part will have big differences when the inclined angle of the sheet is different. Therefore, four different tilted sheets with inclined angles of 15°, 20°, 25°, and 30° were used to study the influence of sheet tilting on forming quality by using 1060 Aluminum sheet as the forming sheet in single point CNC incremental forming. First, the influence of four different inclined angles of the sheet on the overall thickness distribution, plastic strain, and material flow of the formed part was studied by using numerical simulation. Then, the influence of four different inclined angles of sheets on the profile accuracy and thickness thinning rate of the formed part was studied through single point incremental forming experiments. The research results show that sheet tilting has little effect on the profile accuracy of the formed part, but has a great influence on the material flow, plastic strain, and thickness distribution.

Influence of the road profile accuracy on disturbance compensation in active suspension systems

By applying disturbance feedforward control in active suspension systems, knowledge of the road profile can be used to increase ride comfort and safety. As the assumed road profile will never match the real one perfectly, we examine the performance of different disturbance compensators under various deteriorations of the assumed road profile using both synthetic and measured profiles and two quarter vehicle models of different complexity. While a generally valid statement on the maximum tolerable deterioration cannot be made, we identify particularly critical factors and derive recommendations for practical use.

Piezoelectric Active Damper for Surface Roughness Improvement in Hard Turning Processes

Surface roughness and profile accuracy on rolling or sliding surfaces are critical for the wear and fatigue of a component. A high roughness or poor profile accuracy results in higher friction and higher wear rate of the surface. One of the major factors affecting the surface roughness is chatter vibrations. This paper presents a novel design and development of an active damper for chatter suppression of hard turning processes using a piezoelectric actuator and strain signal for chatter detection. The active damper consists of a piezoelectric actuator with an embedded strain gauge for measuring the vibration displacement. In this work, the radial strain signal as a result of radial chatter vibrations from the strain gauge is used as a feedback signal to the actuator using a feedback controller. The experimental results showed a significant suppression in chatter vibrations and improvement of surface roughness using the proposed active damper. The details of the tool design, control design, hardware implementation and system validation are given hereinafter.

Theoretical modeling and experimental research on the depth of radial material removal for flexible grinding

Abrasive belt flap wheel has large elastic deformation, which can better fit the surface of aero-engine blades. Reasonable control of the depth of radial material removal can effectively improve the grinding efficiency and profile accuracy of the blade surface. The depth of radial material removal for flexible grinding was studied through the process parameters in this article. First, the material removal rate model was established based on Hertz elastic contact theory and Preston equation. Then, according to the principle of equivalent material removal volume, a noval approach to determine the depth of radial material removal was proposed. Finally, the experiments for both plane and surface were implemented on a vertical machining center. The results indicate that the proposed method can improve the accuracy and consistency for flexible grinding.

Design of Precision Finishing Method for Cold Extruded Sun Gear With Internal External Tooth Shapes

Due to the complex metal flow in the cold extrusion of sun gear, the teeth accuracy of formed sun gear is poor. In order to improve the accuracy of the extruded sun gear, a novel precision f inishing method was proposed in this study. A new finite element ( prediction strategy was developed to obtain an in-depth understanding of the deviation distribution laws of the finished sun gear. Then, the forming laws of internal-external gears such as material flow, tooth deformation, forming load and tooth accuracy were analyzed using FE simulation and verified experiment. The investigation results show that the single deviations in profile and helix both first diminished remar ka bly , and then rose gradually while the single M value deviation decreased remarkably with increasing the tooth width The simulation results of teeth deviations are well agreed with the experimental ones, which verifies the reliability of the FE prediction strategy Moreover, the profile accuracy of external gear can be improved from ninth to seventh class, lead accuracy can be enhanced from tenth to eighth class, and total M value deviation of internal spline is reduced to 72.3 μm which proves the feasibility and effectiveness of t he precision finishing method