Stuart Feldman - Academia.edu (original) (raw)
Papers by Stuart Feldman
SSRN Electronic Journal, 2011
Nature Human Behaviour, Mar 13, 2023
SSRN Electronic Journal
We explore the commonalities between methods for assuring the security of computer systems (cyber... more We explore the commonalities between methods for assuring the security of computer systems (cybersecurity) and the mechanisms that have evolved through natural selection to protect vertebrates against pathogens, and how insights derived from studying the evolution of natural defenses can inform the design of more effective cybersecurity systems. More generally, security challenges are crucial for the maintenance of a wide range of complex adaptive systems, including financial systems, and again lessons learned from the study of the evolution of natural defenses can provide guidance for the protection of such systems.
arXiv (Cornell University), Nov 3, 2021
Social media are decentralized, interactive, and transformative, empowering users to produce and ... more Social media are decentralized, interactive, and transformative, empowering users to produce and spread information to influence others. This has changed the dynamics of political communication that were previously dominated by traditional corporate news media. Having hundreds of millions of tweets collected over the 2016 and 2020 U.S. presidential elections gave us a unique opportunity to measure the change in polarization and the diffusion of political information. We analyze the diffusion of political information among Twitter users and investigate the change of polarization between these elections and how this change affected the composition and polarization of influencers and their retweeters. We identify "influencers" by their ability to spread information and classify them into those affiliated with a media organization, a political organization, or unaffiliated. Most of the top influencers were affiliated with media organizations during both elections. We found a clear increase from 2016 to 2020 in polarization among influencers and among those whom they influence. Moreover, 75% of the top influencers in 2020 were not present in 2016, demonstrating that such status is difficult to retain.
ArXiv, 2016
IT-driven innovation is an enormous factor in the worldwide economic leadership of the United Sta... more IT-driven innovation is an enormous factor in the worldwide economic leadership of the United States. It is larger than finance, construction, or transportation, and it employs nearly 6% of the US workforce. The top three companies, as measured by market capitalization, are IT companies - Apple, Google (now Alphabet), and Microsoft. Facebook, a relatively recent entry in the top 10 list by market capitalization has surpassed Walmart, the nation's largest retailer, and the largest employer in the world. The net income of just the top three exceeds $80 billion - roughly 100 times the total budget of the NSF CISE directorate which funds 87% of computing research. In short, the direct return on federal research investments in IT research has been enormously profitable to the nation. The IT industry ecosystem is also evolving. The time from conception to market of successful products has been cut from years to months. Product life cycles are increasingly a year or less. This change h...
ACM SIGNUM Newsletter, 1979
Most programming languages seem to take a grudging approach to floating point computation. Many p... more Most programming languages seem to take a grudging approach to floating point computation. Many processors support these operations, and some peculiar and important users insist on using them, so languages provide some facility for using floating point entities. But very little care seems to be taken with numeric issues. Part of the problem is the wide range of anomalous hardware that must be made to "fit" the language. A language definition can be very vague (the most popular approach), or it can cover the limitations and anomalies by a careful specification (as in Brown's model [1]), or it can restrict its domain to particular hardware (such as the Floating Point Standard). The main impact of the proposed floating point standards may be to force a reconsideration of the role of floating point in programming languages. The following comments apply to all of the major proposals; where details are needed for a specific example, the Kahan, Coonen, and Stone [2] proposal ...
Communications of the ACM, 2008
I am writing this column in my last month as President of ACM. It's been a great opportunity ... more I am writing this column in my last month as President of ACM. It's been a great opportunity to support the Association's many successful programs and to expand and firmly establish new directions. Much has been accomplished, much remains to be done.
Not long ago, the problem of software portability seemed on the way to solution. Now, the need an... more Not long ago, the problem of software portability seemed on the way to solution. Now, the need and demand for portability is enormously greater, but solution seems much further away. Reasons include stricter requirements for portability, different expectations by and of the people doing the work, and a far wider range of environments in which software must function. This paper describes how this came about and modern approaches to the problem. 1. The Innocents Abroad Program portability is an old goal. There have been many notable successes, but there has been a major shift in expectations and satisfaction in the past decade. The flrst efforts were in the areas of mathematical and systems software, and a great deal of l. All the section headings refer to actual works; no prize is offered to those who
Queue, 2005
Quality assurance isn’t just testing, or analysis, or wishful thinking. Although it can be boring... more Quality assurance isn’t just testing, or analysis, or wishful thinking. Although it can be boring, difficult, and tedious, QA is nonetheless essential. Ensuring that a system will work when delivered requires much planning and discipline. Convincing others that the system will function properly requires even more careful and thoughtful effort. QA is performed through all stages of the project, not just slapped on at the end. It is a way of life.
ACM Transactions on Mathematical Software, 1980
This paper presents a language-independent proposal for envtronment parameters and basic function... more This paper presents a language-independent proposal for envtronment parameters and basic functions for floating-point computation, and suggests a speofic representation m terms of generic functions for Fortran 77 The enwronment parameters were introduced m 1967 by Forsythe and Moler, who attributed the essentmls of their theory to Wilkinson These parameters are also used m the PORT mathemaucal subroutine library, with precise definitions in terms of a more recent model of floatingpoint computatmn, and a similar set has been proposed by the IFIP Working Group on Numerical Software. Three of the basra functmns are taken from another proposal by this group, but redefined m terms of the parameters and the model to provide a firm theoretical foundation The other three basic functmns can be expressed in tetras of these, but we feel they should be provided separately for convenience The proposed parameters specify the base of the floating-point number system, the maximum precision consistent with the representational and operatmnal accuracy of the machine, and the maxnnum exponent range within whmh one can compute without fear of overflow, underflow, or unexpected loss of accuracy The proposed functions separate a floating-point number into its constituents, reconstruct a number from those constituents, scale a number by a power of the base, and determine the absolute or relatwe spacing (in the sense of the model) between numbers in the vmmlty of a given number.
ACM SIGPLAN Fortran Forum, 1990
We have produced a program that automatically converts ANSI standard Fortran 77 [1] to C [8]. It ... more We have produced a program that automatically converts ANSI standard Fortran 77 [1] to C [8]. It has converted many Fortran programs without manual intervention; it is easily available --- free of charge (and of warranty) --- by electronic mail and ftp.
Csys, 1990
Not long ago, the problem of software portability seemed on the way to solution. Now, the need an... more Not long ago, the problem of software portability seemed on the way to solution. Now, the need and demand for portability is enormously greater, but solution seems much further away. Reasons include stricter requirements for portability, different expectations by and of the people doing the work, and a far wider range of environments in which software must function. This paper describes how this came about and modern approaches to the problem.
ACM SIGPLAN Notices, 1979
I have recently written a portable compiler [1] for the Fortran 77 language [2]. It attacks an ol... more I have recently written a portable compiler [1] for the Fortran 77 language [2]. It attacks an old language with new tools: the parser is generated automatically from an LALR(1) grammar, the program is produced by code generators designed for another language. These tools proved very valuable, but they are based on theory and experience one or two decades fresher than that underlying Fortran, so they really do not fit this application. The following discusses the approach taken, the ways in which the tools had to be bent to do the job, the properties of Fortran that seem to cause the most trouble, and the costs of writing a portable compiler. It also describes certain aspects of the approach to code generation, since others may wish to use the same tools. This paper does not describe low-level details of the implementation. This compiler is intimately connected with the programming language C[3]. The compiler is written in C, it uses tools written in C, the input/output library uses...
ACM SIGPLAN Notices, 1976
The Fortran Standard is now ten years old, and the XSJ3 Committee has recently published a propos... more The Fortran Standard is now ten years old, and the XSJ3 Committee has recently published a proposal for a new one. Much has been learned about programming during this period. Many Fortran extensions have been implemented in various compilers. We must agree that a new standard is timely. The Committee undertook a Herculean task, for which they deserve great credit. Changing Fortran must be like fighting the Hydra-repairing one problem must introduce two new ones in its place. (We wish they had adopted the Augean Stables approach instead.) The Draft includes some new, good, and long-needed features. The description is far easier to understand than the old one. Unfortunately, many of the confusions in the language persist, though frequently in an attenuated form. Some new features are not added as neatly as one might have wished. The following are one reader's opinions of the proposed language definition.
Seventh IEEE International Conference on E-Commerce Technology (CEC'05)
Proceedings of the 1988 ACM SIGPLAN and SIGOPS workshop on Parallel and distributed debugging - PADD '88, 1988
Typical debugging tools are insufficiently powerful to find the most difficult types of program m... more Typical debugging tools are insufficiently powerful to find the most difficult types of program misbehaviors. We have implemented a prototype of a new debugging system, IGOR, which provides a great deal more useful information and offers new abilities that are quite promising. The system runs fast enough to be quite useful while providing many features that are usually available only in an interpreted environment. We describe here some improved facilities (reverse execution, selective searching of execution history, substitution of data and executable parts of the programs) that are needed for serious debugging and are not found in traditional single-thread debugging tools. With a little help from the operating system, we provide these capabilities at reasonable cost without modifying the executable code and running fairly close to full speed. The prototype runs under the DUNE distributed operating system. The current system only supports debugging of single-thread programs. The paper describes planned extensions to make use of extra processors to speed the system and for applying the technique to multi-thread and time-dependent executions.
ACM SIGSAM Bulletin, 1975
This paper contains a summary of the Altran ( Al gebraic Tran slator) language and system for per... more This paper contains a summary of the Altran ( Al gebraic Tran slator) language and system for performing symbolic computations on algebraic data. We hope we have included enough details to make it easy to understand published Altran programs. To this end, we describe the syntax and semantics of the language and briefly define the available library procedures. We have not included all of the details of error conditions, special cases, and default that a user may need to know to program a complicated problem.
The Computer Journal, 2010
Ad Hoc networks are characterized by fast dynamic changes in the topology of the network. A known... more Ad Hoc networks are characterized by fast dynamic changes in the topology of the network. A known technique to improve QoS is to use Multipath routing where packets (voice/video/…) from a source to a destination travel in two or more maximal disjoint paths. We observe that the need to find a set of maximal disjoint paths can be relaxed by finding a set of paths S wherein only bottlenecked links are bypassed. In the proposed model we assume that there is only one edge along a path in S is a bottleneck and show that by selecting random paths in S the probability that bottlenecked edges get bypassed is high. We implemented this idea in the MRA system which is a highly accurate visual ad hoc simulator currently supporting two routing protocols AODV and MRA. We have extended the MRA protocol to use multipath routing by maintaining a set of random routing trees from which random paths can be easily selected. Random paths are allocated/released by threshold rules monitoring the session quality. The experiments show that: 1) session QoS is significantly improved, 2) the fact that many sessions use multiple paths in parallel does not depredate overall performances, 3) the overhead in maintaining multipath in the MRA algorithm is negligible. 1
SSRN Electronic Journal, 2011
Nature Human Behaviour, Mar 13, 2023
SSRN Electronic Journal
We explore the commonalities between methods for assuring the security of computer systems (cyber... more We explore the commonalities between methods for assuring the security of computer systems (cybersecurity) and the mechanisms that have evolved through natural selection to protect vertebrates against pathogens, and how insights derived from studying the evolution of natural defenses can inform the design of more effective cybersecurity systems. More generally, security challenges are crucial for the maintenance of a wide range of complex adaptive systems, including financial systems, and again lessons learned from the study of the evolution of natural defenses can provide guidance for the protection of such systems.
arXiv (Cornell University), Nov 3, 2021
Social media are decentralized, interactive, and transformative, empowering users to produce and ... more Social media are decentralized, interactive, and transformative, empowering users to produce and spread information to influence others. This has changed the dynamics of political communication that were previously dominated by traditional corporate news media. Having hundreds of millions of tweets collected over the 2016 and 2020 U.S. presidential elections gave us a unique opportunity to measure the change in polarization and the diffusion of political information. We analyze the diffusion of political information among Twitter users and investigate the change of polarization between these elections and how this change affected the composition and polarization of influencers and their retweeters. We identify "influencers" by their ability to spread information and classify them into those affiliated with a media organization, a political organization, or unaffiliated. Most of the top influencers were affiliated with media organizations during both elections. We found a clear increase from 2016 to 2020 in polarization among influencers and among those whom they influence. Moreover, 75% of the top influencers in 2020 were not present in 2016, demonstrating that such status is difficult to retain.
ArXiv, 2016
IT-driven innovation is an enormous factor in the worldwide economic leadership of the United Sta... more IT-driven innovation is an enormous factor in the worldwide economic leadership of the United States. It is larger than finance, construction, or transportation, and it employs nearly 6% of the US workforce. The top three companies, as measured by market capitalization, are IT companies - Apple, Google (now Alphabet), and Microsoft. Facebook, a relatively recent entry in the top 10 list by market capitalization has surpassed Walmart, the nation's largest retailer, and the largest employer in the world. The net income of just the top three exceeds $80 billion - roughly 100 times the total budget of the NSF CISE directorate which funds 87% of computing research. In short, the direct return on federal research investments in IT research has been enormously profitable to the nation. The IT industry ecosystem is also evolving. The time from conception to market of successful products has been cut from years to months. Product life cycles are increasingly a year or less. This change h...
ACM SIGNUM Newsletter, 1979
Most programming languages seem to take a grudging approach to floating point computation. Many p... more Most programming languages seem to take a grudging approach to floating point computation. Many processors support these operations, and some peculiar and important users insist on using them, so languages provide some facility for using floating point entities. But very little care seems to be taken with numeric issues. Part of the problem is the wide range of anomalous hardware that must be made to "fit" the language. A language definition can be very vague (the most popular approach), or it can cover the limitations and anomalies by a careful specification (as in Brown's model [1]), or it can restrict its domain to particular hardware (such as the Floating Point Standard). The main impact of the proposed floating point standards may be to force a reconsideration of the role of floating point in programming languages. The following comments apply to all of the major proposals; where details are needed for a specific example, the Kahan, Coonen, and Stone [2] proposal ...
Communications of the ACM, 2008
I am writing this column in my last month as President of ACM. It's been a great opportunity ... more I am writing this column in my last month as President of ACM. It's been a great opportunity to support the Association's many successful programs and to expand and firmly establish new directions. Much has been accomplished, much remains to be done.
Not long ago, the problem of software portability seemed on the way to solution. Now, the need an... more Not long ago, the problem of software portability seemed on the way to solution. Now, the need and demand for portability is enormously greater, but solution seems much further away. Reasons include stricter requirements for portability, different expectations by and of the people doing the work, and a far wider range of environments in which software must function. This paper describes how this came about and modern approaches to the problem. 1. The Innocents Abroad Program portability is an old goal. There have been many notable successes, but there has been a major shift in expectations and satisfaction in the past decade. The flrst efforts were in the areas of mathematical and systems software, and a great deal of l. All the section headings refer to actual works; no prize is offered to those who
Queue, 2005
Quality assurance isn’t just testing, or analysis, or wishful thinking. Although it can be boring... more Quality assurance isn’t just testing, or analysis, or wishful thinking. Although it can be boring, difficult, and tedious, QA is nonetheless essential. Ensuring that a system will work when delivered requires much planning and discipline. Convincing others that the system will function properly requires even more careful and thoughtful effort. QA is performed through all stages of the project, not just slapped on at the end. It is a way of life.
ACM Transactions on Mathematical Software, 1980
This paper presents a language-independent proposal for envtronment parameters and basic function... more This paper presents a language-independent proposal for envtronment parameters and basic functions for floating-point computation, and suggests a speofic representation m terms of generic functions for Fortran 77 The enwronment parameters were introduced m 1967 by Forsythe and Moler, who attributed the essentmls of their theory to Wilkinson These parameters are also used m the PORT mathemaucal subroutine library, with precise definitions in terms of a more recent model of floatingpoint computatmn, and a similar set has been proposed by the IFIP Working Group on Numerical Software. Three of the basra functmns are taken from another proposal by this group, but redefined m terms of the parameters and the model to provide a firm theoretical foundation The other three basic functmns can be expressed in tetras of these, but we feel they should be provided separately for convenience The proposed parameters specify the base of the floating-point number system, the maximum precision consistent with the representational and operatmnal accuracy of the machine, and the maxnnum exponent range within whmh one can compute without fear of overflow, underflow, or unexpected loss of accuracy The proposed functions separate a floating-point number into its constituents, reconstruct a number from those constituents, scale a number by a power of the base, and determine the absolute or relatwe spacing (in the sense of the model) between numbers in the vmmlty of a given number.
ACM SIGPLAN Fortran Forum, 1990
We have produced a program that automatically converts ANSI standard Fortran 77 [1] to C [8]. It ... more We have produced a program that automatically converts ANSI standard Fortran 77 [1] to C [8]. It has converted many Fortran programs without manual intervention; it is easily available --- free of charge (and of warranty) --- by electronic mail and ftp.
Csys, 1990
Not long ago, the problem of software portability seemed on the way to solution. Now, the need an... more Not long ago, the problem of software portability seemed on the way to solution. Now, the need and demand for portability is enormously greater, but solution seems much further away. Reasons include stricter requirements for portability, different expectations by and of the people doing the work, and a far wider range of environments in which software must function. This paper describes how this came about and modern approaches to the problem.
ACM SIGPLAN Notices, 1979
I have recently written a portable compiler [1] for the Fortran 77 language [2]. It attacks an ol... more I have recently written a portable compiler [1] for the Fortran 77 language [2]. It attacks an old language with new tools: the parser is generated automatically from an LALR(1) grammar, the program is produced by code generators designed for another language. These tools proved very valuable, but they are based on theory and experience one or two decades fresher than that underlying Fortran, so they really do not fit this application. The following discusses the approach taken, the ways in which the tools had to be bent to do the job, the properties of Fortran that seem to cause the most trouble, and the costs of writing a portable compiler. It also describes certain aspects of the approach to code generation, since others may wish to use the same tools. This paper does not describe low-level details of the implementation. This compiler is intimately connected with the programming language C[3]. The compiler is written in C, it uses tools written in C, the input/output library uses...
ACM SIGPLAN Notices, 1976
The Fortran Standard is now ten years old, and the XSJ3 Committee has recently published a propos... more The Fortran Standard is now ten years old, and the XSJ3 Committee has recently published a proposal for a new one. Much has been learned about programming during this period. Many Fortran extensions have been implemented in various compilers. We must agree that a new standard is timely. The Committee undertook a Herculean task, for which they deserve great credit. Changing Fortran must be like fighting the Hydra-repairing one problem must introduce two new ones in its place. (We wish they had adopted the Augean Stables approach instead.) The Draft includes some new, good, and long-needed features. The description is far easier to understand than the old one. Unfortunately, many of the confusions in the language persist, though frequently in an attenuated form. Some new features are not added as neatly as one might have wished. The following are one reader's opinions of the proposed language definition.
Seventh IEEE International Conference on E-Commerce Technology (CEC'05)
Proceedings of the 1988 ACM SIGPLAN and SIGOPS workshop on Parallel and distributed debugging - PADD '88, 1988
Typical debugging tools are insufficiently powerful to find the most difficult types of program m... more Typical debugging tools are insufficiently powerful to find the most difficult types of program misbehaviors. We have implemented a prototype of a new debugging system, IGOR, which provides a great deal more useful information and offers new abilities that are quite promising. The system runs fast enough to be quite useful while providing many features that are usually available only in an interpreted environment. We describe here some improved facilities (reverse execution, selective searching of execution history, substitution of data and executable parts of the programs) that are needed for serious debugging and are not found in traditional single-thread debugging tools. With a little help from the operating system, we provide these capabilities at reasonable cost without modifying the executable code and running fairly close to full speed. The prototype runs under the DUNE distributed operating system. The current system only supports debugging of single-thread programs. The paper describes planned extensions to make use of extra processors to speed the system and for applying the technique to multi-thread and time-dependent executions.
ACM SIGSAM Bulletin, 1975
This paper contains a summary of the Altran ( Al gebraic Tran slator) language and system for per... more This paper contains a summary of the Altran ( Al gebraic Tran slator) language and system for performing symbolic computations on algebraic data. We hope we have included enough details to make it easy to understand published Altran programs. To this end, we describe the syntax and semantics of the language and briefly define the available library procedures. We have not included all of the details of error conditions, special cases, and default that a user may need to know to program a complicated problem.
The Computer Journal, 2010
Ad Hoc networks are characterized by fast dynamic changes in the topology of the network. A known... more Ad Hoc networks are characterized by fast dynamic changes in the topology of the network. A known technique to improve QoS is to use Multipath routing where packets (voice/video/…) from a source to a destination travel in two or more maximal disjoint paths. We observe that the need to find a set of maximal disjoint paths can be relaxed by finding a set of paths S wherein only bottlenecked links are bypassed. In the proposed model we assume that there is only one edge along a path in S is a bottleneck and show that by selecting random paths in S the probability that bottlenecked edges get bypassed is high. We implemented this idea in the MRA system which is a highly accurate visual ad hoc simulator currently supporting two routing protocols AODV and MRA. We have extended the MRA protocol to use multipath routing by maintaining a set of random routing trees from which random paths can be easily selected. Random paths are allocated/released by threshold rules monitoring the session quality. The experiments show that: 1) session QoS is significantly improved, 2) the fact that many sessions use multiple paths in parallel does not depredate overall performances, 3) the overhead in maintaining multipath in the MRA algorithm is negligible. 1