A 3-approximation algorithm for the facility location problem with uniform capacities
Mathematical Programming, 2012
ABSTRACT We consider the facility location problem where each facility can serve at most U client... more ABSTRACT We consider the facility location problem where each facility can serve at most U clients. We analyze a local search algorithm for this problem which uses only the operations of add, delete and swap and prove that any locally optimum solution is no more than 3 times the global optimum. This improves on a result of Chudak and Williamson who proved an approximation ratio of ${3+2\sqrt{2}}$ for the same algorithm. We also provide an example which shows that any local search algorithm which uses only these three operations cannot achieve an approximation guarantee better than 3.
A 3Approximation for Facility Location with Uniform Capacities
Integer Programming and Combinatorial Optimization, 2010
We consider the facility location problem where each facility can serve at most U clients. We ana... more We consider the facility location problem where each facility can serve at most U clients. We analyze a local search algorithm for this problem which uses only the operations of add, delete and swap and prove that any locally optimum solution is no more than 3 times the global optimum. This improves on a result of Chudak and Williamson who proved an approximation ratio of \(3+2\sqrt{2}\) for the same algorithm. We also provide an example which shows that our analysis is tight.
A 3-approximation algorithm for the facility location problem with uniform capacities
Mathematical Programming, 2012
ABSTRACT We consider the facility location problem where each facility can serve at most U client... more ABSTRACT We consider the facility location problem where each facility can serve at most U clients. We analyze a local search algorithm for this problem which uses only the operations of add, delete and swap and prove that any locally optimum solution is no more than 3 times the global optimum. This improves on a result of Chudak and Williamson who proved an approximation ratio of ${3+2\sqrt{2}}$ for the same algorithm. We also provide an example which shows that any local search algorithm which uses only these three operations cannot achieve an approximation guarantee better than 3.
A 3Approximation for Facility Location with Uniform Capacities
Integer Programming and Combinatorial Optimization, 2010
We consider the facility location problem where each facility can serve at most U clients. We ana... more We consider the facility location problem where each facility can serve at most U clients. We analyze a local search algorithm for this problem which uses only the operations of add, delete and swap and prove that any locally optimum solution is no more than 3 times the global optimum. This improves on a result of Chudak and Williamson who proved an approximation ratio of \(3+2\sqrt{2}\) for the same algorithm. We also provide an example which shows that our analysis is tight.
A 3-approximation algorithm for the facility location problem with uniform capacities
Mathematical Programming, 2012
ABSTRACT We consider the facility location problem where each facility can serve at most U client... more ABSTRACT We consider the facility location problem where each facility can serve at most U clients. We analyze a local search algorithm for this problem which uses only the operations of add, delete and swap and prove that any locally optimum solution is no more than 3 times the global optimum. This improves on a result of Chudak and Williamson who proved an approximation ratio of ${3+2\sqrt{2}}$ for the same algorithm. We also provide an example which shows that any local search algorithm which uses only these three operations cannot achieve an approximation guarantee better than 3.
A 3Approximation for Facility Location with Uniform Capacities
Integer Programming and Combinatorial Optimization, 2010
We consider the facility location problem where each facility can serve at most U clients. We ana... more We consider the facility location problem where each facility can serve at most U clients. We analyze a local search algorithm for this problem which uses only the operations of add, delete and swap and prove that any locally optimum solution is no more than 3 times the global optimum. This improves on a result of Chudak and Williamson who proved an approximation ratio of \(3+2\sqrt{2}\) for the same algorithm. We also provide an example which shows that our analysis is tight.
A 3-approximation algorithm for the facility location problem with uniform capacities
Mathematical Programming, 2012
ABSTRACT We consider the facility location problem where each facility can serve at most U client... more ABSTRACT We consider the facility location problem where each facility can serve at most U clients. We analyze a local search algorithm for this problem which uses only the operations of add, delete and swap and prove that any locally optimum solution is no more than 3 times the global optimum. This improves on a result of Chudak and Williamson who proved an approximation ratio of ${3+2\sqrt{2}}$ for the same algorithm. We also provide an example which shows that any local search algorithm which uses only these three operations cannot achieve an approximation guarantee better than 3.
A 3Approximation for Facility Location with Uniform Capacities
Integer Programming and Combinatorial Optimization, 2010
We consider the facility location problem where each facility can serve at most U clients. We ana... more We consider the facility location problem where each facility can serve at most U clients. We analyze a local search algorithm for this problem which uses only the operations of add, delete and swap and prove that any locally optimum solution is no more than 3 times the global optimum. This improves on a result of Chudak and Williamson who proved an approximation ratio of \(3+2\sqrt{2}\) for the same algorithm. We also provide an example which shows that our analysis is tight.
A 3-approximation algorithm for the facility location problem with uniform capacities
Mathematical Programming, 2012
ABSTRACT We consider the facility location problem where each facility can serve at most U client... more ABSTRACT We consider the facility location problem where each facility can serve at most U clients. We analyze a local search algorithm for this problem which uses only the operations of add, delete and swap and prove that any locally optimum solution is no more than 3 times the global optimum. This improves on a result of Chudak and Williamson who proved an approximation ratio of ${3+2\sqrt{2}}$ for the same algorithm. We also provide an example which shows that any local search algorithm which uses only these three operations cannot achieve an approximation guarantee better than 3.
A 3Approximation for Facility Location with Uniform Capacities
Integer Programming and Combinatorial Optimization, 2010
We consider the facility location problem where each facility can serve at most U clients. We ana... more We consider the facility location problem where each facility can serve at most U clients. We analyze a local search algorithm for this problem which uses only the operations of add, delete and swap and prove that any locally optimum solution is no more than 3 times the global optimum. This improves on a result of Chudak and Williamson who proved an approximation ratio of \(3+2\sqrt{2}\) for the same algorithm. We also provide an example which shows that our analysis is tight.
Scientific metadata containing semantic descriptions of scientific data is expensive to capture a... more Scientific metadata containing semantic descriptions of scientific data is expensive to capture and is typically not used across entire data analytic processes. We present an approach where semantic metadata is generated as scientific data is being prepared, and then subsequently used to configure models and to customize them to the data. The metadata captured includes sensor descriptions, data characteristics, data types, and process documentation. This metadata is then used in a workflow system to select analytic models dynamically and to set up model parameters automatically. In addition, all aspects of data processing are documented, and the system is able to generate extensive provenance records for new data products based on the metadata. As a result, the system can dynamically select analytic models based on the metadata properties of the data it is processing, generating more accurate results. We show results in analyzing stream metabolism for watershed ecosystem management.
Proceedings of the 1st ACM SIGSPATIAL International Workshop on Spatial Semantics and Ontologies - SSO '11, 2011
Using today's GIS tools, users without programming expertise are unable to fully exploit the grow... more Using today's GIS tools, users without programming expertise are unable to fully exploit the growing amount of geospatial data becoming available because today's tools limit them to displaying data as layers for a region on a map. Fusing the data in more complex ways requires the ability to invoke processing algorithms and to combine the data these algorithms produce in sophisticated ways. Our approach, implemented in a tool called Karma, encapsulates these algorithms as Web services described using semantic models that not only specify the data types for the inputs and outputs, but also specify the relationships between them. Karma semi-automatically builds these models from sample data and then uses these models to provide an easy to use interface that lets users seamlessly implement workflows that combine and process the data in sophisticated ways.
Linked data continues to grow at a rapid rate, but a limitation of a lot of the data that is bein... more Linked data continues to grow at a rapid rate, but a limitation of a lot of the data that is being published is the lack of a semantic description. There are tools, such as D2R, that allow a user to quickly convert a database into RDF, but these tools do not provide a way to easily map the data into an existing ontology. This paper presents a semiautomatic approach to map structured sources to ontologies in order to build semantic descriptions (source models). Since the precise mapping is sometimes ambiguous, we also provide a graphical user interface that allows a user to interactively refine the models. The resulting source models can then be used to convert data into RDF with respect to a given ontology or to define a SPARQL end point that can be queried with respect to an ontology. We evaluated the overall approach on a variety of sources and show that it can be used to quickly build source models with minimal user interaction.
Proceedings of the Workshop on Linked Science (Submitted for review), 2011
The Linked Open Data continues to grow rapidly, but a limitation of much of the data that is bein... more The Linked Open Data continues to grow rapidly, but a limitation of much of the data that is being published is the lack of a semantic description. While there are tools that help users to quickly convert a database into RDF, they do not provide a way to easily map the data into an existing ontology. This paper presents an approach that allows users to interactively map their structured sources into an existing ontology and then use that mapping to generate RDF triples. This approach automatically generates a mapping from the data source into the ontology, but since the precise mapping is sometimes ambiguous, we allow the user to interactively refine the mappings. We implemented this approach in a system called Karma, and demonstrate that the system can map sources into an ontology with minimal user interaction and efficiently generate the corresponding RDF.
Stress urinary incontinence in the prostate cancer survivor
Current Opinion in Urology, 2014
Urinary incontinence after treatment for prostate cancer is common, and the burden of disease is ... more Urinary incontinence after treatment for prostate cancer is common, and the burden of disease is substantial with an increasing number of prostate cancer survivors. We aim to review recent advances in this field with a focus on therapeutic surgical interventions and their outcomes. Recent studies have proven the efficacy of the male transobturator sling while elucidating the prognostic factors associated with its failure. Heavy incontinence and radiation history are strongly associated with poor outcomes after a sling. The artificial urinary sphincter continues to provide excellent outcomes even in patients with prior sling failure. A new quadratic sling has been introduced to the market, but clinical outcomes data are sparse. The use of urethral bulking and oral medicines for stress incontinence remains low because of inconsistent results. Stress urinary incontinence after prostate cancer treatment is common. Fortunately, there are excellent options for managing stress urinary incontinence in men, and recent data have allowed us to approach this problem in a systematic, algorithmic fashion.
Improving Intermittent Androgen-Deprivation Therapy: OFF Cycle and the Role of Steroid 5α-Reductase Inhibitors
Intermittent androgen-deprivation therapy (IADT) consists of cycles of androgen-deprivation (ON c... more Intermittent androgen-deprivation therapy (IADT) consists of cycles of androgen-deprivation (ON cycle) and treatment-free periods (OFF cycle), and is under investigation as a means to improve quality of life and retard progression to castration-recurrent prostate cancer in patients with advanced prostate cancer. IADT appears to be as effective as continuous androgen-deprivation therapy, while improving the side-effect profile. During the OFF cycle of IADT, the androgen-deprived prostate cancer cells are re-exposed to androgens. This milieu of androgen-induced regrowth provides a unique window of opportunity for designing OFF cycle-specific interventions. Testosterone, relative to dihydrotestosterone (DHT), is more potent in the induction of growth suppressive androgen-response genes during regrowth of regressed prostate. These findings suggest that during the OFF cycle of IADT, steroid 5α-reductase (SRD5A) inhibitors can be used to enhance the expression of tumor suppressive androgen-response genes and retard tumor growth by blocking conversion of testosterone to DHT. This chapter discusses how addition of SRD5A inhibitors during the OFF cycle of IADT could improve survival under certain clinical conditions. The molecular changes that accompany treatment suggest that prolongation of the OFF cycle may not be advisable.
BACKGROUND-We have previously reported that finasteride administration in intermittent androgen d... more BACKGROUND-We have previously reported that finasteride administration in intermittent androgen deprivation therapy (IADT) can improve survival of nude mice bearing LNCaP xenograft tumors when the duration of off-cycle in IADT was fixed. A recent retrospective study showed that addition of finasteride doubled the duration of the off-cycle, without changing progression to castration resistance. In view of the above difference, we attempted to investigate the relationship of 5α-reductase inhibition with the off-cycle interval and overall survival in a murine model.
BACKGROUND-Intermittent androgen deprivation therapy (IADT) was developed to improve the quality ... more BACKGROUND-Intermittent androgen deprivation therapy (IADT) was developed to improve the quality of life and retard prostate cancer progression to castration resistance. IADT involves regrowth of the tumor during the off cycle upon testosterone recovery. Our previous studies showed that testosterone is more potent than dihydrotestosterone (DHT) in the induction of a subset of androgen-responsive genes during rat prostate regrowth. However, it is not clear if the same phenomenon would occur during androgen-induced regrowth of prostate tumors. Understanding the differences between testosterone and DHT in inducing androgen-responsive genes during prostate tumor regrowth may provide new insight for improving IADT.
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Papers by Shubham Gupta