Achieving High-Performance the Functional Way: A Functional Pearl on Expressing High-Performance Optimizations as Rewrite Strategies

Optimizing programs to run efficiently on modern parallel hardware is hard but crucial for many applications. The predominantly used imperative languages - like C or OpenCL - force the programmer to intertwine the code describing functionality and optimizations. This results in a portability nightmare that is particularly problematic given the accelerating trend towards specialized hardware devices to further increase efficiency. Many emerging DSLs used in performance demanding domains such as deep learning or high-performance image processing attempt to simplify or even fully automate the optimization process. Using a high-level - often functional - language, programmers focus on describing functionality in a declarative way. In some systems such as Halide or TVM, a separate schedule specifies how the program should be optimized. Unfortunately, these schedules are not written in well-defined programming languages. Instead, they are implemented as a set of ad-hoc predefined APIs that the compiler writers have exposed. In this functional pearl, we show how to employ functional programming techniques to solve this challenge with elegance. We present two functional languages that work together - each addressing a separate concern. RISE is a functional language for expressing computations using well known functional data-parallel patterns. ELEVATE is a functional language for describing optimization strategies. A high-level RISE program is transformed into a low-level form using optimization strategies written in ELEVATE . From the rewritten low-level program high-performance parallel code is automatically generated. In contrast to existing high-performance domain-specific systems with scheduling APIs, in our approach programmers are not restricted to a set of built-in operations and optimizations but freely define their own computational patterns in RISE and optimization strategies in ELEVATE in a composable and reusable way. We show how our holistic functional approach achieves competitive performance with the state-of-the-art imperative systems Halide and TVM

Declining mortality following acute myocardial infarction in the Department of Veterans Affairs Health Care System

<p>Abstract</p> <p>Background</p> <p>Mortality from acute myocardial infarction (AMI) is declining worldwide. We sought to determine if mortality in the Veterans Health Administration (VHA) has also been declining.</p> <p>Methods</p> <p>We calculated 30-day mortality rates between 2004 and 2006 using data from the VHA External Peer Review Program (EPRP), which entails detailed abstraction of records of all patients with AMI. To compare trends within VHA with other systems of care, we estimated relative mortality rates between 2000 and 2005 for all males 65 years and older with a primary diagnosis of AMI using administrative data from the VHA Patient Treatment File and the Medicare Provider Analysis and Review (MedPAR) files.</p> <p>Results</p> <p>Using EPRP data on 11,609 patients, we observed a statistically significant decline in adjusted 30-day mortality following AMI in VHA from 16.3% in 2004 to 13.9% in 2006, a relative decrease of 15% and a decrease in the odds of dying of 10% per year (p = .011). Similar declines were found for in-hospital and 90-day mortality.</p> <p>Based on administrative data on 27,494 VHA patients age 65 years and older and 789,400 Medicare patients, 30-day mortality following AMI declined from 16.0% during 2000-2001 to 15.7% during 2004-June 2005 in VHA and from 16.7% to 15.5% in private sector hospitals. After adjusting for patient characteristics and hospital effects, the overall relative odds of death were similar for VHA and Medicare (odds ratio 1.02, 95% C.I. 0.96-1.08).</p> <p>Conclusion</p> <p>Mortality following AMI within VHA has declined significantly since 2003 at a rate that parallels that in Medicare-funded hospitals.</p

Ethnic differences in satisfaction and quality of life in veterans with ischemic heart disease.

OBJECTIVE: To assess differences in self-reported health status and satisfaction between African-American and caucasian veterans with ischemic heart disease (IHD). DATA SOURCES/STUDY SETTING: African-American and caucasian patients enrolled in General Internal Medicine clinics at six Veteran Affairs Medical Centers. STUDY DESIGN: We conducted a cross-sectional analysis of baseline survey data from the Ambulatory Care Quality Improvement Project (ACQUIP). Patients who responded to an initial health-screening questionnaire were sent follow-up surveys, which included the Medical Outcomes Study 36-item Health Survey (SF-36), the Seattle Outpatient Satisfaction Questionnaire (SOSQ), and the Seattle Angina Questionnaire (SAQ). PRINCIPAL FINDINGS: Of the 44,965 patients approached, 27,977 (62%) returned the baseline survey, of which 10,385 patients reported IHD and were sent the SAQ. Of those, 7,985 patients (84% caucasian, 16% African-American) responded. Caucasian respondents tended to be older, married, nonsmokers, with annual incomes over dollar 10,000, and had higher educational attainment than African Americans. African-American patients reported significantly fewer cardiac procedures (33% vs. 52%, p < 0.001) but were more likely to have diabetes (37% vs. 28%, p < 0.001) and hypertension (81% vs. 68%, p < 0.001). After adjustment for demographic characteristics, comorbid conditions, clinic site, and site-ethnicity interactions, SF-36 scores for physical function, role physical, bodily pain, and vitality were greater for African Americans than caucasians, while adjusted scores were significantly lower for role emotional. However, because of the site-ethnicity interaction, scores varied significantly by site. For the SAQ, overall adjusted physical function summary scores and disease stability scores were significantly greater for African Americans than caucasians. Adjusted summary satisfaction scores for provider satisfaction were not significantly lower for African Americans overall but were significant at two of six sites. Similarly, on the SAQ, adjusted treatment satisfaction scores were significantly lower for African Americans at half of the sites and minimally but not clinically significant overall. CONCLUSIONS: Despite a higher prevalence of cardiac risk factors, African-American patients with CAD who were treated in the VA system appeared to have a greater level of physical functioning, vitality, and angina stability. After adjustment for confounding demographic variables, however, these differences were not consistently significant at all geographic locations. This suggests that many other sociodemographic variables, in addition to ethnicity, influence apparent discrepancies in quality of life, satisfaction, and angina

Transforming self-rated health and the SF-36 scales to include death and improve interpretability

BACKGROUND: Most measures of health-related quality of life are undefined for people who die. Longitudinal analyses are often limited to a healthier cohort (survivors) that cannot be identified prospectively, and that may have had little change in health. OBJECTIVE: To develop and evaluate methods to transform a single self-rated health item (excellent to poor; EVGGFP) and the physical component score of the SF-36 (PCS) to new variables that include a defensible value for death. METHODS: Using longitudinal data from two large studies of older adults, health variables were transformed to the probability of being healthy in the future, conditional on the current observed value; death then has the value of 0. For EVGGFP, the new transformations were compared with some that were published earlier, based on different data. For the PCS, how well three different transformations, based on different definitions of being healthy, discriminated among groups of patients, and detected change in time were assessed. RESULTS: The new transformation for EVGGFP was similar to that published previously. Coding the 5 categories as 95, 90, 80, 30, and 15, and coding dead as 0 is recommended. The three transformations of the PCS detected group differences and change at least as well as the standard PCS. CONCLUSION: These easily interpretable transformed variables permit keeping persons who die in the analyses. Using the transformed variables for longitudinal analyses of health when deaths occur, either for secondary or primary analysis, is recommended. This approach can be applied to other measures of health

Regional Variation in Health Status among Chronic Obstructive Pulmonary Disease Patients

Background: Little is known about geographic differences in health status among patients with chronic obstructive pulmonary disease (COPD). Objectives: The aim of this study was to examine regional variations in self-reported health status of COPD patients at 7 Veterans Affairs clinics. Methods: The Ambulatory Care Quality Improvement Project was a multicenter, randomized trial conducted from 1997 to 2000 that evaluated a quality improvement intervention in the primary care setting. Four thousand and nine participants with COPD (age 6 45 years) completed the Seattle Obstructive Lung Disease Questionnaire (SOLDQ) and 2,991 also completed the Medical Outcomes Study 36-item short form (SF-36). The unadjusted maximal difference in health status scores is reported as the ratio of the highest and lowest site prevalence. We report the maximal site difference in mean health status scores after adjusting for demographics, comorbidities, utilization, medication use and clinic factors. Results: Subjects were predominantly older (66.5 +/- 9.2 years) Caucasian (83.2%) men (97.9%). After adjustment, the maximal site difference for each health status score was significant (p < 0.01) but larger for the SOLDQ (physical 11.2, emotional 9.7, coping skills 7.6) than for the SF-36 (physical component summary 4.7, mental component summary 2.6). Most of the health status variation was explained by individual or clinic level factors, not clinic site. Conclusions: Our models explained < 30% of variation in health status measures; therefore, future studies should consider additional predictors of health status such as physical performance, social determinants of health, COPD treatment and environmental factors. Despite its limitations, this study suggests a need to consider regional differences in health status when comparing COPD health outcomes in diverse geographic areas. Copyright (C) 2010 S. Karger AG, Base

Inhaled Corticosteroids and Risk of Lung Cancer among Patients with Chronic Obstructive Pulmonary Disease

Rationale and Objectives: Lung cancer is a frequent cause of death among patients with chronic obstructive pulmonary disease (COPD). We examined whether the use of inhaled corticosteroids among patients with COPD was associated with a decreased risk of lung cancer