Training Support Vector Machines Using Frank-Wolfe Optimization Methods

Training a Support Vector Machine (SVM) requires the solution of a quadratic programming problem (QP) whose computational complexity becomes prohibitively expensive for large scale datasets. Traditional optimization methods cannot be directly applied in these cases, mainly due to memory restrictions. By adopting a slightly different objective function and under mild conditions on the kernel used within the model, efficient algorithms to train SVMs have been devised under the name of Core Vector Machines (CVMs). This framework exploits the equivalence of the resulting learning problem with the task of building a Minimal Enclosing Ball (MEB) problem in a feature space, where data is implicitly embedded by a kernel function. In this paper, we improve on the CVM approach by proposing two novel methods to build SVMs based on the Frank-Wolfe algorithm, recently revisited as a fast method to approximate the solution of a MEB problem. In contrast to CVMs, our algorithms do not require to compute the solutions of a sequence of increasingly complex QPs and are defined by using only analytic optimization steps. Experiments on a large collection of datasets show that our methods scale better than CVMs in most cases, sometimes at the price of a slightly lower accuracy. As CVMs, the proposed methods can be easily extended to machine learning problems other than binary classification. However, effective classifiers are also obtained using kernels which do not satisfy the condition required by CVMs and can thus be used for a wider set of problems

A Novel Frank-Wolfe Algorithm. Analysis and Applications to Large-Scale SVM Training

Recently, there has been a renewed interest in the machine learning community for variants of a sparse greedy approximation procedure for concave optimization known as {the Frank-Wolfe (FW) method}. In particular, this procedure has been successfully applied to train large-scale instances of non-linear Support Vector Machines (SVMs). Specializing FW to SVM training has allowed to obtain efficient algorithms but also important theoretical results, including convergence analysis of training algorithms and new characterizations of model sparsity. In this paper, we present and analyze a novel variant of the FW method based on a new way to perform away steps, a classic strategy used to accelerate the convergence of the basic FW procedure. Our formulation and analysis is focused on a general concave maximization problem on the simplex. However, the specialization of our algorithm to quadratic forms is strongly related to some classic methods in computational geometry, namely the Gilbert and MDM algorithms. On the theoretical side, we demonstrate that the method matches the guarantees in terms of convergence rate and number of iterations obtained by using classic away steps. In particular, the method enjoys a linear rate of convergence, a result that has been recently proved for MDM on quadratic forms. On the practical side, we provide experiments on several classification datasets, and evaluate the results using statistical tests. Experiments show that our method is faster than the FW method with classic away steps, and works well even in the cases in which classic away steps slow down the algorithm. Furthermore, these improvements are obtained without sacrificing the predictive accuracy of the obtained SVM model.Comment: REVISED VERSION (October 2013) -- Title and abstract have been revised. Section 5 was added. Some proofs have been summarized (full-length proofs available in the previous version

Nationwide analysis of laparoscopic groin hernia repair in Italy from 2015 to 2020

Since its introduction, the minimally invasive treatment of groin hernias has become widely accepted as a viable alternative to open surgery. Still, the rates and reasons for its adoption vary highly among countries and the regions within a country. After almost thirty years since its introduction, its spread is still limited. The present study, conducted under the auspices of AGENAS (Italian National Agency for Regional Services), aims at giving a snapshot of the spreading of minimally invasive and robotic techniques for the treatment of groin hernia in Italy. This study is retrospective, with data covering the period from 1st January 2015 to 31st December 2020. AGENAS provided data using the operation and diagnosis codes used at discharge and reported in the International Classification of Diseases 9th revision (ICD9 2002 version). Admissions performed on an outpatient basis, i.e., without an overnight stay of at least one night in hospital, were excluded. A total of 33,925 laparoscopic hernia repairs were performed during the considered period. Overall, a slight increase in the number of procedures performed was observed from 2015 to 2019, with a mean annual change of 8.60% (CI: 6.46-10.74; p < 0.0001). The number of laparoscopic procedures dropped in 2020, and when considering the whole period, the mean annual change was - 0.98% (CI: - 7.41-5.45; p < 0.0001). Urgent procedures ranged from 335 in 2015 to 508 in 2020 referring to absolute frequencies, and from 0.87% to 9.8% in relative frequencies of overall procedures in 2017 and 2020, respectively (mean = 4.51%; CI = 3.02%-6%; p < 0.001). The most relevant observation that could be made according to our analysis was that the adoption of the laparoscopic approach knew a slow but steady increase from 2015 onward

Nationwide analysis of inpatient laparoscopic ventral hernia repair in Italy from 2015 to 2020

Since 2010, several guidelines and consensus papers have been proposed to support surgeons in the decision-making process (Cuccurullo et al. in Hernia 17(5):557-566, 2013; Silecchia et al. in Surg Endosc 29:2463-2484, 2015; Bittner et al. in Surg Endosc 33(11):3511-3549, 2015) with the conclusion that laparoscopic repair (LR) has gained popularity in the treatment of IH.To date, however, it is not yet clear as to the uptake of LR for IH on national basis. Only dated studies encompassing of all types of incisional hernia repairs are available in literature (Bisgaard et al. in Br J Surg 96:1452-1457, 2009). The aim of our study is to present a snapshot of Italian data for LR of ventral hernias, over a 6 years period, including volume of LR, procedural features and major postoperative outcomes. Data were extracted from the Italian Hospital Information System (HIS) that collects clinical and administrative information regarding each hospital admission of every patient discharged from any hospital in Italy. Using Hospital Discharge records regional Databases (HDD), all laparoscopic ventral hernia procedures carried out in public and private hospitals between 2015 and 2020, in patients over 18 years and resident in Italy, were collected based on diagnosis and procedure codes. The National Agency for Regional Health Services (AgeNaS) oversees the management and analysis of data. All hospital admissions that occurred between 2015 and 2020 were analyzed.A total of 154,546 incisional hernia repairs were performed in Italy from 2015 to 2020. Of these, 20,789 (13.45%) were minimally invasive repairs. The number of procedures performed increased significantly over time, constituting 11.96 and 15.24% of all procedures performed in 2015 and 2020 respectively. However, considering the whole period, the mean annual change was-5.58% (CI - 28.6% to 17.44%; p < 0.0001).Urgent minimally invasive repairs were performed in 1968 cases (1.27%). The absolute rate of laparoscopically treated patients needing an urgent surgical procedure increased overtime (from 7.36% in 2015 to 13.418% in 2020). The mean annual change registered over the whole period was 7.42%. 92% (CI - 0.03 to 14.09%; p < 0.0001). However, when considering the period from 2015 to 2019, the mean annual change was 10.42% (CI 6.35 to 14.49%; p < 0.0001). To our knowledge this is the first nationwide Italian report presenting the national workload of surgical units and the main perioperative features of minimally invasive surgery for ventral hernia repairs

Appendectomy during the COVID-19 pandemic in Italy: a multicenter ambispective cohort study by the Italian Society of Endoscopic Surgery and new technologies (the CRAC study)

Major surgical societies advised using non-operative management of appendicitis and suggested against laparoscopy during the COVID-19 pandemic. The hypothesis is that a significant reduction in the number of emergent appendectomies was observed during the pandemic, restricted to complex cases. The study aimed to analyse emergent surgical appendectomies during pandemic on a national basis and compare it to the same period of the previous year. This is a multicentre, retrospective, observational study investigating the outcomes of patients undergoing emergent appendectomy in March-April 2019 vs March-April 2020. The primary outcome was the number of appendectomies performed, classified according to the American Association for the Surgery of Trauma (AAST) score. Secondary outcomes were the type of surgical technique employed (laparoscopic vs open) and the complication rates. One thousand five hundred forty one patients with acute appendicitis underwent surgery during the two study periods. 1337 (86.8%) patients met the inclusion criteria: 546 (40.8%) patients underwent surgery for acute appendicitis in 2020 and 791 (59.2%) in 2019. According to AAST, patients with complicated appendicitis operated in 2019 were 30.3% vs 39.9% in 2020 (p = 0.001). We observed an increase in the number of post-operative complications in 2020 (15.9%) compared to 2019 (9.6%) (p < 0.001). The following determinants increased the likelihood of complication occurrence: undergoing surgery during 2020 (+ 67%), the increase of a unit in the AAST score (+ 26%), surgery performed > 24 h after admission (+ 58%), open surgery (+ 112%) and conversion to open surgery (+ 166%). In Italian hospitals, in March and April 2020, the number of appendectomies has drastically dropped. During the first pandemic wave, patients undergoing surgery were more frequently affected by more severe appendicitis than the previous year's timeframe and experienced a higher number of complications. Trial registration number and date: Research Registry ID 5789, May 7th, 2020

Low-pressure versus standard-pressure pneumoperitoneum in laparoscopic cholecystectomy: a systematic review and meta-analysis of randomized controlled trials

Introduction: It has been previously demonstrated that the rise of intra-abdominal pressures and prolonged exposure to such pressures can produce changes in the cardiovascular and pulmonary dynamic which, though potentially well tolerated in the majority of healthy patients with adequate cardiopulmonary reserve, may be less well tolerated when cardiopulmonary reserve is poor. Nevertheless, theoretically lowering intra-abdominal pressure could reduce the impact of pneumoperitoneum on the blood circulation of intra-abdominal organs as well as cardiopulmonary function. However, the evidence remains weak, and as such, the debate remains unresolved. The aim of this systematic review and meta-analysis was to demonstrate the current knowledge around the effect of pneumoperitoneum at different pressures levels during laparoscopic cholecystectomy. Materials and methods: This systematic review and meta-analysis were reported according to the recommendations of the 2020 updated Preferred Reporting Items for Systematic reviews and Meta-analyses (PRISMA) guidelines, and the Cochrane handbook for systematic reviews of interventions. Results: This systematic review and meta-analysis included 44 randomized controlled trials that compared different pressures of pneumoperitoneum in the setting of elective laparoscopic cholecystectomy. Length of hospital, conversion rate, and complications rate were not significantly different, whereas statistically significant differences were observed in post-operative pain and analgesic consumption. According to the GRADE criteria, overall quality of evidence was high for intra-operative bile spillage (critical outcome), overall complications (critical outcome), shoulder pain (critical outcome), and overall post-operative pain (critical outcome). Overall quality of evidence was moderate for conversion to open surgery (critical outcome), post-operative pain at 1 day (critical outcome), post-operative pain at 3 days (important outcome), and bleeding (critical outcome). Overall quality of evidence was low for operative time (important outcome), length of hospital stay (important outcome), post-operative pain at 12 h (critical outcome), and was very low for post-operative pain at 1 h (critical outcome), post-operative pain at 4 h (critical outcome), post-operative pain at 8 h (critical outcome), and post-operative pain at 2 days (critical outcome). Conclusions: This review allowed us to draw conclusive results from the use of low-pressure pneumoperitoneum with an adequate quality of evidence

Policy options to support the rural job opportunities creation strategy in Ethiopia

In 2017, the Ministry of Agriculture and Natural Resources of Ethiopia adopted the Rural Job Opportunity Creation Strategy (RJOCS) to address a lack of job opportunities in rural areas and its related effects such as migration to urban areas and poverty. This report, using a dynamic computable general equilibrium model tailored to the Ethiopian context, quantifies several policy options in terms of jobs opportunity creation. This report aims to quantify six policy options employing a dynamic Computable General Equilibrium model developed by the Joint Research Centre (JRC) tailored to the Ethiopian context. The analysis of the Ethiopian economy through multipliers base on a specifically developed database shows that livestock has the greatest employment generation capacity, followed by cash crops, food crops and agri-food industry. This means that polices which focus on rural and agri-food sectors should have great potential to create job opportunities. All scenarios show the capacity of the Ethiopian agriculture and food industry to generate job opportunities and improve condition of workers and their families, with particular positive effects under scenario subsidising agroparks and developing workers skills through education.JRC.D.4-Economics of Agricultur