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Constructible function

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390: 574: 527: 499: 70:). The purpose of such a definition is to exclude functions that do not provide an upper bound on the runtime of some Turing machine. 552: 358:) can be time-constructible unless it is eventually constant, since there is insufficient time to read the entire input. However, 193:) steps. This definition is slightly less general than the first two but, for most applications, either definition can be used. 31: 579: 452: 403: 78:
There are two different definitions of a time-constructible function. In the first definition, a function
448:
for which the theorem is true. Time-constructible functions are often used to provide such a definition.
406:. They are important because the time hierarchy theorem relies on Turing machines that must determine in 469: 548: 523: 495: 350: 363: 154:)) time (a unary representation may be used instead, since the two can be interconverted in 17: 43: 408: 269: 142: 59: 568: 402:
Time-constructible functions are used in results from complexity theory such as the
444:. To formulate them precisely, it is necessary to have a precise definition for 465: 436:) in that time. Such results are typically true for all natural functions 169:
There is also a notion of a fully time-constructible function. A function
428:) steps. This is, of course, impossible without being able to calculate 451:
Space-constructible functions are used similarly, for example in the
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which, given a string 1, outputs the binary representation of
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Balcázar, José Luis; Díaz, Josep; Gabarró, Joaquim (1988).
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This article incorporates material from constructible on
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but not necessarily true for artificially constructed
259:
ones, outputs the binary (or unary) representation of
366: 332:, 2) are time- and space-constructible, as long as 492:Computational Complexity: A Conceptual Perspective 384: 494:. Cambridge University Press. pp. 130, 139. 420:)) time whether an algorithm has taken more than 470:Creative Commons Attribution/Share-Alike License 8: 46:to natural numbers with the property that 365: 518:Homer, Steven; Selman, Alan L. (2011). 477: 120:. In the second definition, a function 296:which, given a string 1 consisting of 255:which, given a string 1 consisting of 220:which, given a string 1 consisting of 181:which, given a string 1 consisting of 97:which, given a string 1 consisting of 7: 513: 511: 485: 483: 481: 520:Computability and Complexity Theory 394:is a space-constructible function. 209:if there exists a positive integer 86:if there exists a positive integer 25: 292:if there exists a Turing machine 251:if there exists a Turing machine 177:if there exists a Turing machine 128:if there exists a Turing machine 316:All the commonly used functions 300:ones, halts after using exactly 224:ones, halts after using exactly 575:Computational complexity theory 197:Space-constructible definitions 468:, which is licensed under the 379: 373: 74:Time-constructible definitions 1: 522:(Second ed.). Springer. 348:> 0. No function which is 27:Concept in complexity theory 243:. Equivalently, a function 36:time-constructible function 18:Time-constructible function 596: 185:ones, stops after exactly 101:ones, stops after exactly 54:) can be constructed from 290:fully space-constructible 490:Goldreich, Oded (2008). 175:fully time-constructible 545:Structural Complexity I 453:space hierarchy theorem 385:{\displaystyle \log(n)} 404:time hierarchy theorem 386: 201:Similarly, a function 387: 216:and a Turing machine 62:in the time of order 446:a natural function f 364: 267:), while using only 547:. Springer-Verlag. 249:space-constructible 207:space-constructible 93:and Turing machine 580:Types of functions 382: 126:time-constructible 84:time-constructible 529:978-1-4614-0681-5 501:978-0-521-88473-0 284:Also, a function 32:complexity theory 16:(Redirected from 587: 559: 558: 540: 534: 533: 515: 506: 505: 487: 393: 391: 389: 388: 383: 232:) cells for all 109:) steps for all 21: 595: 594: 590: 589: 588: 586: 585: 584: 565: 564: 563: 562: 555: 542: 541: 537: 530: 517: 516: 509: 502: 489: 488: 479: 461: 400: 362: 361: 359: 344:for a constant 314: 242: 215: 199: 119: 92: 76: 44:natural numbers 28: 23: 22: 15: 12: 11: 5: 593: 591: 583: 582: 577: 567: 566: 561: 560: 553: 535: 528: 507: 500: 476: 475: 460: 457: 399: 396: 381: 378: 375: 372: 369: 340:) is at least 313: 310: 240: 213: 198: 195: 117: 90: 75: 72: 60:Turing machine 38:is a function 26: 24: 14: 13: 10: 9: 6: 4: 3: 2: 592: 581: 578: 576: 573: 572: 570: 556: 554:3-540-18622-0 550: 546: 539: 536: 531: 525: 521: 514: 512: 508: 503: 497: 493: 486: 484: 482: 478: 474: 473: 471: 467: 458: 456: 454: 449: 447: 443: 439: 435: 431: 427: 423: 419: 415: 411: 410: 405: 397: 395: 376: 370: 367: 357: 353: 352: 347: 343: 339: 335: 331: 327: 323: 319: 311: 309: 307: 303: 299: 295: 291: 287: 282: 280: 276: 272: 271: 266: 262: 258: 254: 250: 246: 239: 235: 231: 227: 223: 219: 212: 208: 204: 196: 194: 192: 188: 184: 180: 176: 172: 167: 165: 161: 157: 153: 149: 145: 144: 139: 135: 131: 127: 123: 116: 112: 108: 104: 100: 96: 89: 85: 81: 73: 71: 69: 65: 61: 57: 53: 49: 45: 41: 37: 33: 19: 544: 538: 519: 491: 463: 462: 450: 445: 441: 437: 433: 429: 425: 421: 417: 413: 407: 401: 398:Applications 355: 349: 345: 341: 337: 333: 329: 325: 321: 317: 315: 305: 301: 297: 293: 289: 285: 283: 278: 274: 268: 264: 260: 256: 252: 248: 244: 237: 233: 229: 225: 221: 217: 210: 206: 202: 200: 190: 186: 182: 178: 174: 170: 168: 163: 159: 155: 151: 147: 141: 137: 133: 129: 125: 121: 114: 110: 106: 102: 98: 94: 87: 83: 79: 77: 67: 63: 55: 51: 47: 39: 35: 29: 324:) (such as 569:Categories 466:PlanetMath 459:References 281:)) space. 173:is called 166:)) time). 124:is called 82:is called 371:⁡ 308:) cells. 312:Examples 392:⁠ 360:⁠ 551:  526:  498:  140:) in 58:by a 42:from 549:ISBN 524:ISBN 496:ISBN 34:, a 368:log 288:is 247:is 205:is 30:In 571:: 510:^ 480:^ 455:. 342:cn 328:, 236:≥ 113:≥ 557:. 532:. 504:. 472:. 442:f 438:f 434:n 432:( 430:f 426:n 424:( 422:f 418:n 416:( 414:f 412:( 409:O 380:) 377:n 374:( 356:n 354:( 351:o 346:c 338:n 336:( 334:f 330:n 326:n 322:n 320:( 318:f 306:n 304:( 302:f 298:n 294:M 286:f 279:n 277:( 275:f 273:( 270:O 265:n 263:( 261:f 257:n 253:M 245:f 241:0 238:n 234:n 230:n 228:( 226:f 222:n 218:M 214:0 211:n 203:f 191:n 189:( 187:f 183:n 179:M 171:f 164:n 162:( 160:f 158:( 156:O 152:n 150:( 148:f 146:( 143:O 138:n 136:( 134:f 130:M 122:f 118:0 115:n 111:n 107:n 105:( 103:f 99:n 95:M 91:0 88:n 80:f 68:n 66:( 64:f 56:n 52:n 50:( 48:f 40:f 20:)

Index

Time-constructible function
complexity theory
natural numbers
Turing machine
O
O
o
time hierarchy theorem
O
space hierarchy theorem
PlanetMath
Creative Commons Attribution/Share-Alike License



ISBN
978-0-521-88473-0


ISBN
978-1-4614-0681-5
ISBN
3-540-18622-0
Categories
Computational complexity theory
Types of functions

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